Finalist: Yaroslav Trofimov and James Marson of The Wall Street Journal

By James Marson

SULYHIVKA, Ukraine—The messages arriving on Viktor Yatsunyk’s phone were vague and worrisome. Somewhere nearby, Ukrainian soldiers had triggered a land mine and lay dead or injured.

The onetime carpenter and his teammates, who included a store-sign maker, a boxing enthusiast and a computer-science student, converged on a map reference in a beat-up crossover and a pickup truck.

When other army units needed something hazardous done on the eastern front, they called this group. The team of more than 100 had retrieved bodies from no man’s land, led assaults on villages and crept through forests to hunt Russians with aerial drones. And they had won, repelling Russia’s advance in Ukraine’s northeastern Kharkiv region.

Viktor wrote to one of the group’s commanders on the Signal messaging app acknowledging, with a code, the information and the task. “++,” he typed.

The 44-year-old led seven soldiers in single file along the edge of a field in search of the casualties. A Wall Street Journal team followed behind.

The men knew the villages and fields in the area well. When Russian troops were around, a hamlet to the south had become the team’s home, and the forests and fields their terrain.

Viktor, who had served as a reservist in the British army, was a leader within the group. Known as Britanets, or Brit, for his secondary allegiance, he had lived in the U.K. for a quarter-century and received a British passport. He spoke with a London accent and served guests tea with milk. But his mother, who raised him alone with a passion for Ukrainian folk songs, had instilled in him a patriotism that never faded.

When the war started he headed to Ukraine to fight. The unit he joined in the east was dominated by men who made up for their limited military experience with bravery that verged on recklessness. The group was named Skala, or the Rock, after its leader, a giant army major with a passing resemblance to the actor Dwayne “The Rock” Johnson. He pulled together men of similar spirit from wherever he could, and provided them with a steady supply of equipment and food.

The recent Russian retreat had eased months of high tension. That September day, some of the men weren’t wearing body armor. Some wore T-shirts. One waved a metal detector, but it wasn’t much use and he stowed it.

As the team walked along the road, they passed burned-out armored vehicles, antitank mines and discarded weapons and clothes. Recent rain had turned the path to thick mud, which clumped on the men’s boots as they walked. Where recently artillery and tank guns had raged, there was little sound but for a light breeze in the trees.

The team approached a curve about 500 yards down the track. I assumed the casualties would be around the bend.

An explosion flashed, cracked and shook the ground. I ducked instinctively, even though it was little more impressive than a large firecracker.

The echo of the blast faded to silence. Smoke drifted in from the trees to the right. Several soldiers had dropped to the sodden earth. Britanets lay motionless on his left side. Surely they will get up, I thought.

A volunteer army

Over 10 months, Ukraine has stunned the world with its military success, which includes reclaiming half the territory it lost during the initial phase of Russia’s invasion.

The Ukrainian effort relies heavily on volunteer units grafted onto the professional army. A novel military experiment driven at first by expediency, the decentralized command has since given Ukraine a crucial advantage in tackling the lumbering Russian military.

The units are often named for their commanders, such as Skala. They work with volunteers who raise funds and provide equipment, such as drones, power banks and pickup trucks. The soldiers are enlisted and follow the standard chain of command, but have broad latitude to pick tasks, coordinate with other units on the ground and figure out how best to get jobs done.

Ukraine has plenty of experienced soldiers—it has fought a low-level war against Russian paramilitaries in the east since 2014. But Russia is girding for a protracted conflict, calling up 300,000 reservists and moving the economy to a war footing. Ukraine can’t afford to lose personnel through carelessness.

As many as 13,000 Ukrainian troops have been killed, officials say, and tens of thousands more have been wounded, taken prisoner or are missing. Many are inexperienced former civilians who learned on the job. Of eight members of one team in Skala’s group, only two remain at the front. Three have been killed, two are no longer physically fit for service and one is recovering in the hospital.

Members of Skala’s group sport badges emblazoned with two antitank weapons and a drone. Asked about the most important asset of his unit, Skala said: “My people.”

“For me as a commander the main thing is to keep my soldiers alive and to defeat the enemy completely,” he said.

‘Who wants to start a war?’

It was a few days after Russia invaded on Feb. 24 when Viktor left the farmhouse where he lived in Oxfordshire, England, to head to war. He wasn’t the type to sit idle when something needed doing, his wife Yulia told me. On a visit to the care home last December where she worked, he told her he didn’t want to end up like the old folks sitting silent and immobile.

“I want to die like a hero so my kids know I did something for the country,” he said.

“What are you talking about?” Yulia retorted. “Nobody’s going to die in a war. Who wants to start a war these days?”

After Viktor headed to the airport, Yulia felt confident he would be OK because he was always careful. In his job as a carpenter he would repeatedly check measurements before drilling a hole, she said.

Arriving in Ukraine, where he became Britanets, he joined with James Vasquez, a retired U.S. Army staff sergeant from Norwalk, Conn., who had come to volunteer his fighting skills. They hit it off and headed to Kyiv to join some of Britanets’s friends, who were based out of an auto-repair shop. They started ambushing Russian units with the help of antitank missiles. It was this kind of entrepreneurial warfare that characterized the early stages of the conflict.

Their comrades had little experience. One wore sneakers and a bright red top into early battles. “You are going to get us f—ing killed!” the American admonished him.

After one skirmish, Britanets shot a video of his U.S. teammate standing in front of a destroyed Russian tank. “Welcome to America!” Britanets called out from behind the camera.

Britanets would call Yulia on WhatsApp, his eyes shining, and gush about his teammates and the feeling of camaraderie.

“I can’t believe you went to Ukraine, to a war, where people are dying, and you’re so happy there,” she told him.

Skala gathers

After Russian forces retreated from Kyiv at the end of March, Britanets headed east to Barvinkove, a town of some 8,000, named for a 17th-century Cossack leader who founded it as a stronghold. For the Russians it was a new target.

If Russia could take the town, they could strike south and link up with troops slicing northward. That would trap some of Ukraine’s best military units in the east, where many had been fighting for years.

Britanets joined a crew whose job was to stop them. It was commanded by 33-year-old Maj. Yuriy Harkaviy, or Skala. He and a couple of dozen men had started out the war ambushing Russian tank columns. Now they were helping Ukraine’s 93rd Brigade, a battle-hardened mechanized unit, to keep the Russians north of Barvinkove.

The area saw brutal fighting during World War II and is dotted with memorials. Before the war with Russia, volunteer search teams would still dig up remains of bodies from the black earth.

Skala needed more men. He dispatched an aide to scour enlistment offices for suitable recruits. A local member of his team came across a group of soldiers in a house in Barvinkove attached to no official unit.

The team of eight had arrived from Kyiv. They had served in a volunteer unit named Brotherhood, whose leadership professes a far-right religious nationalism. Many of the men had signed up mainly because it was the quickest way to get their hands on weapons.

Among them was Ivan Shpylyevoi, 32, a gruff boxer who worked in online advertising. Ivan had recently switched from speaking Russian, his mother tongue, to Ukrainian. His mother had brought him up alone and they still lived together. He had started running with a bad crowd in his early 20s and getting into fights, his mom said.

After one trip to pick him up from the police station, his mom sat him down: “In life, I can only help you once, then you’re on your own,” she told him.

Something clicked. He distanced himself from the troublemakers and took up boxing more seriously. Around that time, an elderly neighbor approached his mom. “I want to thank you for your son,” the man told her. Ivan, he said, had fought off some teenagers who had tried to rob him.

At the start of the war, after three days trying and failing to enlist at a recruiting office, Ivan jumped on a train to Kyiv, and signed with Brotherhood. He was soon joined by an 18-year-old camp counselor and trainee auto mechanic called Denys Pankevych. They bonded the first night, sharing a laugh about how Denys had accidentally discharged his rifle into a wall of a university lecture hall where he had been billeted in early March.

Denys took the alias Kontrabas, which means cello but is also slang for contraband, because he used to smuggle cigarettes into Poland. Ivan became Sadist for his stern demeanor and the colorful descriptions of his plans for the Russians.

The reality of war stunned them at first. On an early mission to recapture a village, Kontrabas recalls taking cover from mortar fire behind a wall for 15 minutes in a stupor. “I prayed to everyone I could remember,” he said.

He decided he could just as easily be killed cowering in a bunker, so it was better to fight. He stepped out and began copying the more experienced fighters in his unit. The battle for the village lasted all day, ending with a Ukrainian success.

The group Skala inherited was a mixed bag. There was also Radek, a laconic 39-year-old Polish military veteran. Why was he fighting? “Right thing to do,” he said later. (The Wall Street Journal agreed to use only his first name.) The informal leader was 39-year-old Kostyantyn Rusanov, who lived in a Kyiv suburb with his wife and daughters of 11 and 13, where he ran a business selling store signage. When he enlisted and was asked for his nom de guerre, he responded “Nema,” meaning, “I don’t have one.” It stuck, as Nemo.

“Think hard if you are ready for this,” Skala told them. “It won’t be easy.”

Skala assigned the group a commander from his team and sent them on their first mission in May—to recover the body of a scout from the 93rd Brigade. The team set out on foot using a quadcopter drone to scan for the enemy. They took a rope with them, fearing the Russians could have mined the body. They located him, tied the rope around, and tugged. No explosion. They pulled him onto a stretcher and began to withdraw.

Suddenly, the rifle of one soldier caught on his belt and discharged a round. The noise apparently alerted the Russians, and a firefight broke out with the infantry from the 93rd Brigade, who had followed Skala’s men with the aim of digging a new forward position.

They got away with no losses—by sheer chance. “No one died, there was just a fight, and that’s it,” Nemo said.

Scouting by drone

Russia had an overwhelming advantage in artillery, firing around 10 shells to every one from Ukraine. Ukrainian forces, short on ammunition, focused on accuracy instead, often using drones.

Day after day, Nemo and his crew would head out in a pickup truck, then continue on foot into territory between the front lines to scout Russian positions. They would send the drone up to look for targets and report them back to HQ, a house in a village south of Barvinkove, where commanders would relay the data to artillery gunners. The gunners would correct their own fire from a live stream broadcast from the drone using Elon Musk’s satellite-based internet system, Starlink.

They began losing teammates, including Keks, or Cookie, a pilot, who rushed out on his own with a drone to locate a Russian tank. He had just gotten out of his car when a round exploded nearby, killing him. Another, Shram, or Scar, was sidelined by the lingering effects of injuries from a motorcycle accident he had suffered before the war. Rosomakha, or Wolverine, also quit because of old injuries.

Kontrabas was picked as a drone pilot. He would rather have been on an assault team, he said, for the thrill. When at home he drove at more than 120 miles an hour. “There are no healthy people at war. We are all addicted to something,” he said.

He grew close to Sadist, who became like an elder brother. Sadist had a hard shell but a soft side for those he allowed close. Kontrabas made a video of himself goofing around in a van to music with a cigarette hanging from his lips. Sadist, sitting alongside, glances at him then smiles.

Sadist shot a film of Kontrabas flying a drone. “Our pilot at work. What a hooligan!” he said. “Our little gem.”

Skala’s group had grown in size to more than 100 fighters. In the summer, the Ukrainians went on the offensive. They carefully prepared an assault on Dibrivne, a village to the north of Barvinkove, which would give them access to higher ground.

Nemo’s crew spent five days scouting the village. They located Russian armored vehicles and positions, and directed artillery to hit them. They would spend hours recording video so they had a better idea of the lay of the land.

Soon, Nemo felt he knew exactly where the hide-outs were. He told Skala they were ready to go.

The assault was led by small groups of Skala’s men, followed by troops from the 93rd Brigade, who were supposed to thrust into the village on foot and meet in the center. Nemo’s task was to lead the infantry to the village, using the knowledge he had gleaned.

As Nemo’s team approached a forest packed with concealed Russian positions, they heard the sound of explosions from the trees. The Russians were fleeing, and in such haste that they triggered their own booby traps.

The Ukrainians entered the abandoned village unscathed. From the heights nearby, they were able to strike farther and more accurately onto lower ground around other Russian-held villages. On one occasion, Kontrabas flew a drone 6 miles, a record for Skala’s pilots, to provide footage that helped artillery gunners destroy several Russian tanks.

On Sept. 10, Nemo and Kontrabas went to scout enemy positions in Brazhkivka, one of the Russian-controlled villages, but couldn’t find any Russians there. “Where the hell are they?” Nemo asked. The Russians had fled.

Tea, anyone?

The mood in Skala’s group was celebratory. They sped around the villages hunting for trophy vehicles left behind by the Russians and toured the places they abandoned.

At the village HQ, Britanets received a fresh consignment of equipment from volunteers with garrulous enthusiasm. He offered cookies and tea—“PG Tips or Yorkshire?”—to his guests, which included the Journal team.

Britanets paused now and then to field calls from men working farther east, where the Russians were trying to break through.

He commiserated with me, a fellow Brit, on the death of Queen Elizabeth II. “A good lady,” he said. He shared military banter with Journal security adviser Lee Brett, a former U.S. Army ranger whose job was to keep the reporting team safe.

Britanets showed us his freshly issued American M4 carbine and complained that it needed more accessories. He stowed it in a case. Then he fetched his Ukrainian-made Vulkan assault rifle and offered it to me to feel its weight. He laughed when I pulled my sleeves over my hands so as not to leave fingerprints.

He took back the weapon and laid it on top of a map marked with Russian positions. I continued to question him about how Skala’s group were using drones. The gun was pointing toward Lee, who raised his eyebrows.

“Oh sorry, mate,” Britanets said. “It’s empty.”

He pulled out the magazine to check the chamber. There was no bullet in the chamber, but the magazine was full.

“Running through your NSPs,” Lee noted, referring to Normal Safety Precautions, a set of basic drills to ensure a firearm is safe.

“Yeah,” said Britanets, before returning to the theme of drones.

Ukraine, he said, needed more equipment from the West because it is like a bodyguard standing between Europe and Russia. “What a price Ukraine pays,” he said.

‘I have to go’

The Ukrainians’ celebratory mood was broken on Sept. 17 by a call from an officer from the 93rd Brigade.

Two officers, a combat engineer known as a sapper and a driver had triggered a mine while scouting for the bodies of men lost during the summer, the officer told a top aide to Skala. Could Skala’s group send a team?

“Britanets, you’re in charge,” said Skala. Britanets pulled on his body armor and helmet.

Just then, our team arrived back at headquarters. “I have to go,” Britanets told me as he walked past.

He jumped into the Kia crossover of a local man who would drive. Three others squeezed in the back: Metr, or Meter, a giant 23-year-old with long hair tied back beneath a bucket hat; Biliy, or White, a computer-science student who played guitar in a funk-jazz band; and Zheka, a thickset man who had been unsteady since he suffered a concussion and had asked not to be sent to the front lines.

The four-person Journal team followed behind with a local video reporter. Britanets tried to call the sapper, who was uninjured, for updates on their position, but couldn’t get through.

We edged across a damaged bridge, then turned right onto a muddy road toward the village of Brazhkivka, where Britanets had raised the Ukrainian flag days earlier. The cars slid from side to side on the muddy road, past two dozen or so incapacitated Russian armored vehicles.

The cars arrived at a fork in the road. One track led left back into the village. The other went straight, with a line of trees to the right. A green pickup sat at the junction with Nemo’s crew—Sadist, Radek and a recent recruit called Chekh, or Czech.

The teams got ready to go. Metr searched, without success, for a USB-C cable to launch a drone. A view from the sky would have told them that the sapper had already dragged the injured man out toward the road we had just left, and that both were safe. Instead, the teams were relying on an outdated map.

Britanets told Nemo he knew the area, Nemo later recalled. “You lead, then,” Nemo told him.

Britanets instructed everyone to leave their weapons in their vehicles. They would likely be pulling people out and would be better off with less gear. He left his helmet behind, as did the others. Some, including Sadist, weren’t wearing body armor. This wasn’t their standard practice.

The soldiers set off along a path between the trees and a field, then turned down an embankment and onto a dirt track.

Britanets turned around to the single file behind him. “Don’t walk too close,” he yelled in English.

The ground was heavy from recent rain and it caked on our boots. After a couple of hundred yards, we came across a line of antitank mines, green metal disks the size of pizzas with fuses in the middle. They are detonated by the weight of a vehicle and can be safely maneuvered around on foot. We shuffled past.

Radek, the Polish veteran, swung a metal detector in front of him. It beeped constantly, rendered worthless by the amount of shrapnel littering the ground. He turned it off. Sadist picked up a Russian rocket launcher as a trophy.

In the lead, Britanets approached a bend. He must have not seen the copper wire in front of him, which was attached to an anti-personnel mine, a rectangular plastic box about the size of a purse. It was concealed behind the grass among the trees 10 yards to the right, its scissor legs dug into the earth to hold it in place.

As Britanets’s leg pushed on the wire, it pulled a pin in the fuse, which released a spring-loaded striker that slammed into the percussion cap and fired the detonator. That set off the charge in the mine and propelled hundreds of tiny pieces of metal in an arc toward Britanets and the soldiers behind him.

Several crumpled to the ground.

All was silent. Britanets didn’t move. Then someone cried: “I’m hit.”

The uninjured men swarmed around the stricken. Nemo, seeing blood soaking the right side of his shirt and pants, managed to tourniquet his leg and arm with help from Metr.

Sadist rose to his knees, grasping his gut. Radek clutched a piece of gauze to his face to try to stem bleeding from his mouth.

Our team had crouched down when the blast hit and remained still, apart from the photographer, who stood up to capture the scene.

“Help us,” Zheka yelled, his eyes wide.

“Stay here,” Lee told us firmly, concerned for our safety. He was worried another mine could be triggered as the men scrambled to help the wounded.

“Check Britanets,” someone said.

Metr walked over and peered at him.

“Half his head is gone,” he cried.

The men couldn’t figure out how to carry out the injured with only three fully healthy soldiers.

“We’re going to have to help carry them,” I said to Lee. I paused: “Well, you tell me.”

“No,” he said. “No. I need you guys out.”

Lee stood up, turned around and went first, inching along the footprints we’d left, checking for more booby traps.

We had got only a few yards when Zheka yelled: “Press! Turn around and come and f—ing help.”

I looked back and saw him struggling to support Nemo, who was limping badly and howling with every step.

“Can I help him with the guy on his shoulder?” I asked Lee. Lee didn’t object.

I put my right arm under Nemo’s left shoulder and around his back. My right hand gripped his clothing damp with blood.

“It’s not far,” I told him as we set off.

I asked his name, told him mine, and asked whether he had children.

“Yes, two,” Nemo grunted.

“OK, we’re walking to your children,” I said.

We found a slow but steady rhythm. His weight dragged down my right side and grew heavier with every step. I tried to keep us moving in a straight line on the trodden path, worried about more mines if we strayed.

We had walked for several minutes when we spotted three armored vehicles laden with soldiers chugging along the track. We halted, and I called for help.

Nemo was weakening. I shoved my shoulder deeper under his to support his weight better. I was panting now. “Come on, you can do it,” I said, to him—and to myself. We made it a few more yards before he collapsed to the ground.

Several of the men had jumped off the armored vehicles and charged down the bank. They began to tend to Nemo, so I scrambled to the relative safety of the track.

Lee was there treating Radek, who had blood dripping from his mouth. A metal fragment was lodged inside. Lee told him to sit and wait for evacuation.

Back where the mine went off, Zheka, Metr and Biliy were struggling with Sadist.

“Guys, I’m f—d, you can just leave me,” Sadist said between groans, Biliy told me later.

They tried to load him on a lightweight canvas stretcher, which ripped. Sadist was covered in mud.

Zheka lifted Sadist’s legs onto his shoulders and Biliy tried to raise his body. “Why are you carrying me?” Sadist protested. “Put me down!”

The troops from the vehicles brought a stretcher and carried him to the road. His face was white, his mouth open and features contorted.

The soldiers laid the stretcher down and we went to help—Lee to provide treatment, me to assist and interpret.

“Keep him steady for me,” Lee said, lifting up Sadist’s T-shirt. A small slit was visible around where his liver was. A tear of blood seeped out.

We rolled him onto his side to check his back for an exit wound. There was none. The fragment must have sliced up his insides.

The muscle-bound boxing enthusiast Sadist was fading. He was no longer speaking Ukrainian but had reverted to the Russian that his mom spoke to her little boy, Ivan.

“Please,” Ivan said weakly. He was clawing at his pants trying to release the pressure from the blood pooling inside his gut.

“Please. F—,” Ivan pleaded, suddenly thrashing with his arms as if trying to haul himself up. “I can’t lie here.”

We pinned his arms and Lee started to apply a bandage and tried to comfort him. We had done what we could.

We went to check on the other casualties. Nemo’s leg wound wasn’t serious, which meant the blood covering him must be coming from his arm, where the tourniquet was loose. Biliy held him from behind and I gripped his arm tight as Lee pulled off the bandage. Blood squirted a foot in the air.

“Tell him this is going to suck,” Lee told me. He took a wad of gauze designed to stop bleeding and shoved it into Nemo’s arm. Nemo screamed.

Lee wrapped a bandage over the top and secured it. “Done, done,” he told the soldier. “The good news is, you’re going to live.”

Lee bandaged up the minor leg wound of Chekh.

Biliy cradled Sadist. He was dead.

Some soldiers lifted him from the stretcher onto a blanket with a picture of a lion. His right arm flopped to the side, revealing a tattoo, which read: “Good luck.”

Skala sped up in his black SUV. He looked worried and needed to take control.

Metr had stayed with Britanets at the bomb site. Others worried the mine had been set off by vibrations and that there were more to come. Skala went to fetch his men. The sapper from the 93rd Brigade—the man whose group had sparked the day’s events—went with him. Skala also took a Russian prisoner the group was holding.

“I can’t risk my people,” he said.

They freed Britanets from the wire, which was wrapped around his boot, covered his head, loaded him onto a stretcher, and brought him back to the road. They lifted him onto the back of a pickup next to Sadist, and covered him with the blue canvas stretcher. His striped gray socks poked out from underneath.

No romanticism

Skala had questions for us when we saw him two days later.

“Why did you go onto the field?” he asked. He was worried he had put us at risk. I reassured him that we were doing our jobs and were aware of the danger.

Our presence there concerned him for another reason: Had Britanets been playing to the press and lost his vigilance? “He’s a character,” Skala said.

It was the group’s first loss to a tripwire, he said. He lamented that the men hadn’t been able to launch the drone, because perhaps then they would have seen the safer route via the main road.

“Carelessness,” he said. “We were heroes, real men. We were relaxed.”

Could Sadist have been saved? No, Lee replied.

The day after the incident, Kontrabas called Sadist’s mother and told her that Ivan was dead. He thought the call was better coming from someone who knew Sadist well, rather than from an unknown officer from HQ. When Kontrabas heard his friend’s mother burst into tears, he felt a surge of guilt. He was alive and hadn’t been there to look out for his friend, who had saved him earlier in the war.

Ivan died as he wanted, his mom said, recalling his words before he set off in February: “Mom, if I die at war, it is the death I want most of all.”

Radek had several operations over the following weeks. The fragment had hit a nerve, paralyzing his face. He had to learn to talk and eat again.

He said lack of training, poor midtier command and a lack of professionalism were costing Ukraine dear. The men were brave, he said, but they were being thrown into a meat grinder that was chewing up young men and experienced fighters.

He said he would go to the front when he recovered. “No romanticism here,” he wrote in a message, “just pragmatism.”

Nemo recovered well. By December he was back on the front lines in the east. “Who else is going to do it?” he said.

Shortly after he returned, another of their crew, a man in his early 30s named Arkhip, was killed in fighting. That left only Nemo and Kontrabas from their original group of eight from Brotherhood still at the front.

In England, Yulia mourned Viktor, Britanets. She knew him as a gregarious but meticulous man. She wondered—had he been so focused on the task of saving others that he had overlooked his own safety?

Viktor’s ashes were buried in his grandmother’s village in western Ukraine, where he had planned to retire with Yulia and renovate his ancestral home. The local mayor granted permission for him to be buried at a memorial for heroes of attempts to establish a Ukrainian state in earlier centuries.

Viktor’s mother fell to her knees in tears in front of the grave. Then dozens of mourners broke into the Ukrainian national anthem, a defiant ode to the price of liberty that includes this penultimate line: “We shall lay down our souls and bodies for our freedom.”

Oksana Grytsenko, Kate Vtorygina and Ievgeniia Sivorka contributed to this article.

Citizen volunteers teamed up with soldiers to turn the tide in the most consequential European battle since World War II

By James Marson

KYIV, Ukraine—Outside the Giraffe shopping mall on the western edge of Ukraine’s capital, a group of locals prepared to meet the Russian armored column thundering their way.

It was late February, and the Russians, from an elite airborne unit, were riding atop their vehicles, as if expecting a warm greeting. One wore a Cossack woolen hat instead of a helmet. Another hadn’t loaded his rifle.

The few dozen Ukrainians from the towns of Irpin and Bucha had other intentions, which they had written on the cement mixer and bulldozer that blocked the road: “Welcome to hell.”

After Russia launched an all-out invasion on Feb. 24, a 32-year-old Ukrainian city council member and solar-power entrepreneur named Volodymyr Korotya had led preparations for a fighting stand. The men were brandishing a grab bag of weapons, including pump-action shotguns and a handful of rocket-propelled grenades. Many were dressed in jeans, and few had body armor. Around half of their number, which included a psychotherapist, a firefighter and a bus driver, had never fought before.

“Look what I do and do the same,” Mr. Korotya, who had seen combat during his time in the Ukrainian army, told the new recruits.

As a vanguard of a dozen armored vehicles rumbled over the bridge between Bucha and Irpin and began to climb the hill toward them, the Ukrainians opened fire.

After a fierce three-hour battle, the Russian vehicles were destroyed or abandoned, and the soldiers were dead or in retreat. The Ukrainians set off across the bridge to finish off the rest of the column.

The Russians never crossed that bridge in their monthlong attempt to seize Kyiv.

It is hard to know how people will react to a huge invasion force. Resistance requires a core of people in villages, towns and cities to find enough courage and motivation to fight rather than flee. Confidence in communities large and small grows with each person who stays and picks up a weapon.

That’s especially true in a country like Ukraine, whose national anthem starts: “The glory and freedom of Ukraine have not yet perished.” That line reflects the nation’s painful attempts over centuries to establish itself as an independent country in the maw of empires.

Russian President Vladimir Putin sent his army into Ukraine to snuff out its latest, 30-year attempt to establish full-fledged independence after the collapse of the Soviet Union. He had boasted that it would take only days for his powerful army to take Kyiv.

Over the next month, enough Ukrainians found the will and means to resist him. They formed armed groups with whatever weapons they could lay their hands on. They fed and equipped fighters and billeted them in their homes. They shimmied up trees in search of cellphone reception to report on enemy movements. The result looked like something little seen in modern warfare—a domestic insurgency fused onto a traditional army.

“We are like a hive of bees,” said Yaroslav Honchar, head of an attack-drone crew who make their own armed craft. “One bee is nothing, but a thousand can defeat a big force.”

To a degree not fully appreciated, it was these citizen soldiers, teaming up with active-duty personnel, who turned the tide in the most consequential battle in Europe since World War II and preserved Ukraine’s status as a sovereign nation. The defense of Kyiv allowed the president to stay and rally national support. He could also then procure the weapons from the U.S. and Europe that are now helping the army to dislodge Russian forces in the east and south.

Without Kyiv’s defenders securing crucial spots around the city in the war’s early days, none of that would have been possible.

Saving the Airport

The Ukrainian special-forces team needed to get to Kyiv fast. But the roads from their base in western Ukraine were choked with cars heading the other way.

Civilians were panicking. Russian armored columns were streaming toward the capital from Belarus, less than 100 miles to the north. Information was scarce and often contradictory.

Marik, the team’s 32-year-old leader, focused. He needed to locate the sharpest Russian thrust toward Kyiv and figure out how his team could blunt it, he explained later, using only a pseudonym as required by Ukraine’s military.

A cyberattack had cut communications between commanders and units in the field, leaving unsecured cellphones as the only link. But Marik saw no reason to panic. He stuck to his mantra: You can’t win the war on your own; everyone has his own small front.

As the team threaded its way toward Kyiv, Marik saw videos posted online by civilians of around 30 black Russian helicopters swooping low toward the capital from the north. Their target was Antonov Airport in Hostomel, a cargo and testing airstrip about 20 miles from central Kyiv.

Marik’s commanders ordered him there. An understrength National Guard unit and another special-forces team at the airport had managed to shoot down three helicopters and hold off 200 elite paratroopers for nearly three hours before withdrawing when they ran out of ammunition. They had lost the airport but won time.

The Russians set up machine-gun nests and secured airport buildings in preparation for transport planes to land a larger force to thrust into the heart of Kyiv.

Marik had to get there and stop them. Arriving near the airport as darkness fell, he learned that others were also gunning for the Russians.

This would be no repeat of 2014, when Russian irregular fighters seized the city of Slovyansk in Ukraine’s east, igniting a war that was still simmering when Russia’s new invasion force rolled in.

Back then, when Marik was sent in to reclaim the city, his unit was equipped mostly with Soviet remnants, including metal helmets and rubber tourniquets that could snap when pulled tight. Now Marik’s men had Kevlar helmets, fitted body armor and secure American radios with headsets. Western training had helped accustom him to working autonomously in small groups. Special forces’ new motto, taken from a 10th-century Kyiv leader called Svyatoslav the Brave, announced their readiness for violence: “I come at you!”

An array of Ukrainian units, aided by civilian volunteers, threw themselves into a haphazard counterattack.

Forty-eight Ukrainian paratroopers landed in three helicopters to the southwest, while another assault team approached from the north. They used brief cellphone messages to direct artillery forces to pound Russian positions. Under assault from several angles, the Russians couldn’t safely land planes.

The counterattack had bought time. But Russian armored columns were advancing quickly by land.

Around dawn, commanders ordered Marik to pull back to a new defensive line along the Irpin River to the northwest of Kyiv. Sappers told him they were preparing to detonate the nearest bridge in 10 minutes, and couldn’t wait.

“Blow it,” Marik said. “We’ll find another way out.”

The explosion rang out as the vehicles sped off. They looped south, but for a second day were delayed by civilians: not ones fleeing, but those who had stayed, picked up assault rifles at their local recruiting offices and set up roadblocks. They wanted to check his documents and, when they found out who he was, pestered him to help them man the barricades.

It was early afternoon by the time he made it to the village of Horenka on the other side of the river, the last significant natural barrier on the western approach to Kyiv. His team hid its vehicles and crept 300 yards onto the bridge.

There, they found corpses in uniforms and burnt-out vehicles—the aftermath of a battle. Documents on bodies from both sides revealed that Ukrainians from the 72nd Mechanized Brigade had held off Russians from police special forces, apparently deployed for a public-order operation in anticipation of a quick military victory.

Civilians were picking their way across the bridge on foot, on bikes and in cars. There was a hole on one side of the road, but it was still passable. Marik called for explosives to finish the job, to deny the Russians the bridge.

The explosives arrived packed in a white van. With the Russians on the far bank, Marik couldn’t risk trying to lay charges under the bridge. Instead, they would have to drive the van onto the side that was still intact and detonate the load.

“Has it all been checked?” he asked the soldier who brought the explosives and detonators.

“Yes, all of it,” came the reply.

Russian helicopters were circling Antonov Airport. The enemy appeared to be in control and bringing forward reserves. There was no time to waste.

Two of Marik’s men drove the van onto the bridge, parking it on the right side and sprinted back, unspooling the detonator wire. With everyone clear, Marik plunged the detonator.

Nothing happened.

Marik cursed.

With every minute that passed, he worried that the Russians, lurking somewhere on the far bank, would launch an attack.

Marik grabbed a detonator set to five minutes and sprinted onto the bridge. He primed it then ran back to cover.

Three minutes had passed when the machine-gunner covering the bridge radioed Marik.

“Civilians moving toward the bridge,” said the soldier, known as Vova.

“Vova, just shoot,” Marik said. “Scare them.”

Vova fired two bursts of bullets. The civilians hit the deck. Seconds later, the van exploded.

After the dust settled, Marik sent up a quadcopter, a small drone with four rotors, to check the damage. There was a big hole in the bridge surrounded by fissures. Tanks wouldn’t be able to pass.

Commanders then ordered him north to prevent the Russians from crossing the river at another spot.

The Dam

Marik needn’t have worried. A 44-year-old property developer named Oleksandr Dmitriyev was already on the case.

A thickset man with a mop of brown hair and blue eyes, Mr. Dmitriyev for years had organized off-road races on the boggy land along the Irpin River.

He knew the Irpin had thwarted German invaders in 1941. Soviet bunkers still dot the eastern bank, part of a defensive stand that forced the Nazis to loop around Kyiv to take it.

When a reservoir was created on the Dnipro River to the capital’s north in the early 1960s, a dam was constructed at the mouth of the Irpin to prevent flooding. Pumps force water from the Irpin into the reservoir, whose level was several meters higher.

If the dam stopped holding the water back, it would flood the banks and create a natural barrier to the Russian advance. Mr. Dmitriyev’s audacious plan: Blow up the dam.

Mr. Dmitriyev headed a volunteer group of auto enthusiasts that had helped re-equip the army after Russia’s first invasion in 2014. He drove to the headquarters of Ukraine’s Ground Forces to pitch his idea.

Army Lt. Gen. Oleksandr Syrskiy listened intently as Mr. Dmitriyev explained with the help of a map. The commander gave the go-ahead.

Soldiers loaded hundreds of pounds of explosives into two of Mr. Dmitriyev’s sport-utility vehicles.

Mr. Dmitriyev called Oleksandr Aleksandrovych, a 41-year-old photographer who was another member of the volunteer group. The photographer made his way to the dam, where his first task was to explain the plan to the two men on duty at the pumping station.

“Are you crazy?” one of them exclaimed. Unleashing the water from the reservoir would flood people’s homes on the river banks.

“I know,” Mr. Aleksandrovych countered. “But this could save their lives.”

A local car mechanic who was part of Mr. Dmitriyev’s group tried an angle grinder and a blowtorch on the sluice gates. No luck.

There was only one option left, Mr. Aleksandrovych told Mr. Dmitriyev by telephone: “We need to blow it.”

As dusk fell, sappers detonated the charges with a bang heard in nearby villages.

Mr. Aleksandrovych went to inspect the result of their work. Water was gushing through a 5-foot hole.

Drone Strike

Early the next morning, on Feb. 26, a group of civilian drone enthusiasts stood on the edge of Moshchun village to the south, staring at images streamed from an octocopter hovering over the opposite bank.

“Jackpot,” said Mr. Honchar, 42. He was a former IT entrepreneur who used technology to make foreign pharmaceutical businesses more efficient. At that moment, dozens of Russian armored vehicles were loitering in fields on the opposite bank, apparently unsure where to go now that the bridges were blown.

It was the moment the Ukrainians had been training for since 2014, when Mr. Honchar and an investment banker friend launched Aerorozvidka, or Aerial Reconnaissance, to give the battered Ukrainian Army an eye in the sky to combat the Russian forces in the east.

Mr. Honchar and fellow drone missionaries would travel the front lines sharing images of enemy positions. They weren’t officially part of the army at first, but they had badges made to look the part, and soldiers and commanders were hungry for their pictures.

They initially used commercial drones and ordered models made by cinematographers. Then they constructed their own R18 octocopter from off-the-shelf and custom-made parts, improving it bit by bit with new components, including a thermal-imaging camera. That allows it to operate under cover of darkness.

The real MacGyver moment was when they figured out how to drop Soviet-era antitank grenades from the drones, using an attachment made from a 3-D printer.

As they stood in the village, Mr. Honchar looked at the drone pilot, a baby-faced 40-year-old known as Frodo, and they grinned. “Now we’re going to blow someone up,” said Mr. Honchar.

Through military contacts, Mr. Honchar had secured five boxes each containing six RKG-3 grenades. They loaded three onto the craft and sent it streaking over the river. Frodo positioned it over a tank, then pressed the button to release the grenade.

They heard an explosion and saw smoke billowing from the vehicle. It was the first time they had taken out a tank. The crew cheered. They reloaded and went out again. On the opposite bank, the tank crews had dismounted and had spotted the noisy craft in the dawn light. On the screen, Frodo saw a crowd of Russian soldiers firing their automatic rifles at the octocopter. Suddenly, they started to lose the connection. The drone went down, but it was a trade they would make any day.

“It wasn’t about how many we killed,” he said, “but letting them know that it wouldn’t be a walk in the park.”

Giraffe Mall

On the other side of the river the morning of Feb. 27, outside the Giraffe shopping mall in the city of Irpin, the local militia was bracing for battle. Its leader, Mr. Korotya, had dusted off his old nom de guerre, Insurgent, which he took on during his youth as a fan of the soccer team Dynamo Kyiv, when he brawled with fans from rival teams.

Now a city councilor in neighboring Bucha, Mr. Korotya had spent the prior three days scrounging for men and munitions.

On the day of the invasion, he met with fellow veterans, then headed to the local military office to ask for rifles. Officers there refused and told them to go to their former army units. Late that evening he took a dozen veterans to the National Guard base in Irpin, which appeared deserted.

The armory was locked, but there were two armored personnel carriers in the garage. They wouldn’t start, so the men brought spare parts from an auto repair shop and set to work fixing them as mortar fire exploded close by.

They got the vehicles running and were preparing to leave when a handful of National Guard troops showed up, stunned to find armed men on their base with the dud vehicles running.

Insurgent gave them one of the APCs but took the other and hid it behind the Giraffe mall.

As morning broke, he heard of more abandoned vehicles up the road toward Antonov Airport. Insurgent’s men set to work getting them moving when an elderly man approached and quizzed them about who they were.

“Gramps, go away,” Insurgent said.

“No, listen,” the man persisted. “We’ve got paratroopers in our basement.”

Insurgent followed him to a house a few hundred yards closer to the airport, where they found eight Ukrainian paratroopers with rifles, a machine gun and rocket-propelled grenade launchers.

Their war had started near Chernobyl on the Belarus border, but they had quickly withdrawn as Russian armored vehicles threatened to overrun them. Part of their unit had been sent to assault Antonov Airport. The remainder set off toward Bucha but was ambushed by mortar fire around 5 a.m.

Insurgent brought the reinforcements and the vehicles that could drive or be towed back to Giraffe.

Other fresh troops were trickling in. Among them was Oleksandr Kotenko, a 42-year-old psychotherapist with a dark goatee and long hair pulled back into a ponytail. He took the name Tango for his love of dancing.

They brought a cement mixer and a bulldozer to block the road. They set up the machine gun and hid their four armored vehicles behind buildings around the mall. Around half of the 70 men were veterans, the rest were raw recruits like Tango who received a few quick tips about fighting, mainly about the importance of avoiding friendly fire.

It was just after 7 a.m. on Feb. 27 when Insurgent got word from an acquaintance at the northern end of Bucha that a huge Russian column was heading toward Station Street.

The roar of dozens of diesel engines grew louder. Then a vanguard of around a dozen vehicles rumbled across the bridge.

As the first vehicle started crawling up the hill, one of the Ukrainian paratroopers fired a rocket-propelled grenade, destroying it in one blow. He quickly picked up another RPG, already loaded, and fired again, hitting a second vehicle.

The rest of the ambush team opened fire with everything they had. The Ukrainian armored vehicles darted forward and let loose with their machine guns, then ducked back behind cover. One of the novices fired a machine gun from behind the roadblock, fed by Tango. When he got shot, Tango dragged him away and patched him up.

The Russians were in disarray. Their vehicles that could still move careened off the road and sought shelter behind buildings, including the shopping mall.

Soon after the shooting began, the mayor of Irpin, city councilors and utilities workers sped up and joined the fight with AK-47 rifles in hand.

With no radios other than the ones in the vehicles, Insurgent yelled commands or passed them on via a runner. Artillery began firing. Insurgent marked coordinates on Google maps and sent them to councilors he knew, who passed them to the military. At one point, they heard violent explosions from the other side of the bridge.

Some Russian soldiers tried to flank the Ukrainians through a deserted brick factory, but Insurgent’s men pushed them back. More than a dozen Russians took shelter in the shopping mall. They appeared unprepared and terrified. One came running out of the building on fire and shooting, until he was cut down. Another who had lost the bottom parts of his legs crawled out and opened fire. Lacking modern tourniquets, the Russians had bound their wounds with tape.

After more than two hours, the fight was over. Insurgent picked through the detritus of battle. Documents identified the Russians as members of the elite 76th Guards Air Assault Division.

He gathered a team of around 30, including newly arrived reinforcements from special forces. “Let’s go and finish them off,” he said.

‘It’s Begun’

Ukrainian forces on the eastern flank of Kyiv didn’t have a river for protection. But they had time.

Russian columns were trundling along a highway from the east. It would be almost two weeks before the first one approached.

A battalion of the 72nd Mechanized Brigade, which defended the capital’s flanks, had set up an ambush there in the first days of the war. Reinforcements arrived in the shape of Tetyana Chornovol, a 42-year-old former investigative journalist.

As a reporter, she scaled the wall of a corrupt, pro-Russian president’s mansion to photograph its opulence. She was beaten by thugs during street protests that ousted that leader. After becoming a lawmaker, she promoted domestic weapons production.

As the Russians gathered forces around Ukraine’s borders last year, she had grown certain they would invade, and she had recently completed a training course on a Ukrainian antitank weapon called a Stugna.

She had been drinking wine with a companion until the wee hours on Feb. 24 and had barely slept when she was roused by a phone call.

“It’s begun,” a friend told her.

Moments later, a missile exploded nearby.

She jumped in her ruby-red hybrid hatchback and set off for the Stugna factory to pick up some missiles.

After a few days searching for action, Ms. Chornovol called an officer in the 72nd Brigade who directed her to Brovary, a city on the eastern edge of Kyiv. A Russian armored column from the 6th Guards Tank Regiment was heading along a highway from the east toward the city.

Preparing its defense was softly spoken 29-year-old Lt. Col. Roman Darmohrai, a battalion commander whose military career had been forged in war. He graduated from the National Army Academy in 2015 and went straight into battle in eastern Ukraine with the 72nd, whose badge bears a skull and the phrase “Ukraine or death.”

After arriving in Brovary, he began laying a trap. The Russian tanks would vastly outnumber his vehicles, so his plans would rely on antitank weapons, surprise and local assistance.

Locals armed with backhoes and shovels helped them dig in.

Lt. Col. Darmohrai positioned Ms. Chornovol in a field near the village of Skybyn, at the front of the main ambush team. They couldn’t light a fire for fear of giving away their positions, so took shelter from the freezing wind in a small concrete irrigation station. She set up her Stugna, an export version that had a digital control screen with text in Arabic, and waited.

They knew the column was coming. Villagers were sending updates by phone and an app that computer whizzes had helped create for the Security Service of Ukraine. On March 9, a column of around two dozen vehicles rolled through the village of Zalissya in the direction of Brovary.

Part of the ambush team was ready at the side of the road, guided by a reconnaissance team using a drone. As the vehicles emerged from behind the tree line, a soldier who until recently had worked as a barista took aim with his NLAW, a shoulder-fired antitank missile provided by the U.K. government.

The missile slammed into the side of a tank. A couple of vehicles veered off into surrounding fields, while others returned fire on the Ukrainian position.

Stunned, most of the column halted. When it regrouped, it was moving in a single line rather than spreading out into a battle formation. As the vehicles approached the next village of Skybyn, Ms. Chornovol opened fire.

Her first shot missed. Her second was a direct hit, her first in battle.

As Ukrainian Korsar missiles landed and artillery guns boomed, the Russian tanks careened onto the muddy roadside. Trying to spin around, they clumped together, providing even juicier targets for Ukrainian gunners.

By the time the column retreated, it had lost 17 tanks, three other armored vehicles and dozens of men.

The vehicle of Russian Army Col. Andrei Zakharov, commander of the 6th Guards Tank Regiment, was among those hit. His men sped him to Bohdanivka, where they pulled up outside a house and ordered the gate opened. The owner, Serhiy Bobko, was a member of the local militia who had fled, but his wife opened up.

“Get us an operating table or something,” ordered one Russian soldier.

Soldiers pulled Col. Zakharov from the vehicle. He was covered in blood that had soaked into the sheet covering him. They were taking him to Mr. Bobko’s barn when he died.

As the Russians carried Col. Zakharov’s body away, one of them turned to Ms. Bobko.

“We no longer have a commander,” the forlorn soldier said. “We don’t know what to do: go forward or back.”

Greek’s Group

Yuriy Ulshyn, better known as Greek, was in Mariupol when the war started, but changed plans when he saw Russian invasion forces streaming toward the capital.

“Guys, let’s go to Kyiv,” he told the dozen teammates on his informal commando team. “If they take Kyiv, then it’s pointless defending elsewhere.”

The 47-year-old geologist, who took his alias from his Greek mother, had been at war for eight years and gained a reputation as a skilled army scout and sniper. He wanted to take the fight to the Russians but despised the paralyzing bureaucracy of the military and preferred to serve as a volunteer, picking where he and his men could work most effectively.

In the early days of March, Greek spotted a weak point that he and his couple of dozen men could help plug. The bridge over the Zhytomyr Highway near Makariv was a prime target for Russian forces seeking to cut off weapons deliveries from the West and advance toward the highway leading south to Odessa. There was a gap there between the 72nd Brigade and its neighboring unit.

He went to see the commander of the 72nd. “Sanya, I’ll go to the other side of the highway,” he said, calling Col. Oleksandr Vdovychenko by his familiar name. “There’s a hole near Makariv.”

His team was small, but then he received an offer of reinforcements from Vasyl Virastyuk, winner of the World’s Strongest Man contest in 2004, who was elected to Parliament in 2021. Mr. Virastyuk recommended a powerlifter called Andriy Kotovenko, better known as Cat, a short, stocky man who used to work at Epicenter, Ukraine’s equivalent of Home Depot.

Cat had been planning to head to Columbus, Ohio, to take part in Arnold Schwarzenegger’s renowned strength competition. Instead, on the first day of war, he went looking for the fastest way onto the front lines.

He called Mr. Virastyuk, who directed him to Greek’s freewheeling band of commandos.

Days later, Cat arrived with his team of six, including a former colleague from Epicenter and an ex-foodstore manager who had fought with him in the east.

They were a neat match: Greek a cerebral player-coach, Cat spoiling for a fight.

“I wake up thinking about killing Russians, and I go to sleep thinking about killing Russians,” Cat would say.

Eight years earlier the military recruiting office had refused to take him because he had no military experience. Instead he had joined Right Sector, a nationalist militia, which was the fastest way to get to the front line.

Right Sector became a boogeyman for the Russians, like the so-called Banderites who followed a nationalist leader and fought the Soviets into the 1950s.

Cat learned to operate a mortar and fought in several hot spots before he was badly injured after a soldier close by stepped on a land mine. He had fought back to health after 22 operations and started a new career as a competitive powerlifter.

Cat got hold of a 120 mm mortar and ammunition that an army unit had seized from the Russians. With the help of volunteers he acquired a Ford Ranger pickup to transport the mortar, and a Land Rover for the rounds.

Operating out of a house offered by a local in a village just to the west of the Makariv bridge, they worked in the gray zone, finding targets for the army’s artillery and for Cat’s mortar. They pushed the Russians back from the bridge to the woods and a hamlet known as the Makariv Dachas.

The Russians moved into houses there and dug into the woods, burying their tanks deep.

“We’ve dug in so well that the Banderites won’t see us,” one of the soldiers told a local villager.

Chernobyl’s Shadow

Frodo, the drone pilot, was in a village nearby, just south of the Zhytomyr Highway, bristling with frustration because wet and foggy weather meant he couldn’t fly his drones.

A commander he knew from his service in the east called with an offer: Would he like to join a team hunting Russians near Chernobyl?

From the first day of war, Russian armored columns had been rumbling toward Kyiv from Belarus down two roads through the area around the defunct nuclear plant.

With the Russian army stuck on the edge of Kyiv, huge tailbacks formed, one of which stretched 40 miles back from Antonov Airport.

Firing on Russian vehicles, the 72nd Brigade’s artillery chief said, was like playing Tetris, the Soviet-designed computer game where a player lines up blocks to make them disappear.

“We eliminated them,” he said, “then new ones appeared.”

The commander who called Frodo, the Russia-born son of a Soviet airman, wanted him on a team of special-forces soldiers, hunters and poachers who would attempt to pinch the flow of vehicles at the source, starving the Russian units ranged around Kyiv of reinforcements, fuel and ammunition.

Frodo and the team of around 20 loaded pickups with equipment including remote-controlled mines and rifles. They also took five terminals to connect up with Starlink, the internet service of Elon Musk’s SpaceX, after a Ukrainian minister tweeted a request to the billionaire. Russia was targeting cell towers and using jamming to cut mobile communications, but Starlink would keep them connected.

They headed toward the village of Bazar in the wooded and sparsely populated area to the west of Chernobyl, where they linked up with Artem Sandratskiy, a 43-year-old hunting-lodge manager who knew the area well.

When Russia invaded, he helped around 1,500 people to flee Russian-held territory via Bazar, which remained under Ukrainian control. He arranged accommodation at the local school and food and clothes from volunteers. He also coaxed information from them, asking them to point to the spots on Google Maps where command posts and vehicles were located.

“I helped everyone,” he said, “and almost everyone helped me.”

He would double check the information with informers on occupied territory. Contacts clambered up trees in search of phone signal to send him messages. Oleksandr Rakov, a 47-year-old baker in the village of Krasyatichi, would share information he had collected on his rounds delivering bread.

Frodo and his crew arrived around March 10. By then, he and other members of Aerorozvidka had signed up with the Security Service of Ukraine to make their service official.

Their first target was a bridge near Poliske, a town near the Belarusian border that was abandoned after the Chernobyl nuclear accident in 1986.

They moved carefully. Frodo sent his drone up to check ahead for enemy troops every half-mile or so. They carried boxes of explosives on quad bikes fitted with mufflers and used them to blow the bridge.

Ideas for missions came thick and fast. They would sit around a table at Mr. Sandratskiy’s house and draw up plans on a map. They sought to target high-value Russian vehicles and equipment, sometimes staying in houses abandoned after the Chernobyl disaster, living right under the Russians’ noses. It wasn’t long before they were targets in a cat-and-mouse game with Russian helicopters, drones and special forces hunting them.

Locals informed them of a juicy target: dozens of ammunition and fuel trucks at a farm near the village of Zirka.

If they could get howitzers close enough and coordinate fire from a drone, it would be a turkey shoot. To succeed, they would have to take the howitzers, which weigh more than six tons each, into a gray zone controlled by neither side without being seen and keep a connection between the drone and the artillery commander giving the orders.

The commander persuaded an army general to provide three 152 mm howitzers with a range of 11 miles. Frodo arranged for a Ukrainian fixed-wing drone called a Leleka, or Stork, to provide live video. Frodo would be in charge of making sure they had a link.

Special-forces soldiers used chain saws to carve a path through the woods for trucks to drag the guns.

In the early hours of March 16, the trucks pulled the guns forward. Frodo went with them. In position a few miles from Zirka, he couldn’t get the Starlink powered from his car, as he’d planned, and had to call for a generator, which was rushed to his position.

As the Leleka was approaching the target around 10 a.m., the connection suddenly appeared.

The artillery commander standing next to the drone pilots called the gunners on Signal on his cellphone and gave the order to fire, directing their aim using the picture from the drone.

A video from the craft posted later on Facebook by Gen. Valeriy Zaluzhniy, the commander-in-chief of Ukraine’s armed forces, shows the destruction. Truck after truck is blown up as the howitzers score 47 hits from 52 shots. Gen. Zaluzhniy’s video is set to the song “Highway to Hell,” by AC/DC.

Peat Bog

By the start of March, the blown bridges had halted the Russians on the Irpin River. The flooding had prevented them from crossing in the north.

Over the following days, Mr. Dmitriyev observed drone footage that showed the river spreading from a channel of some 10 yards, submerging fields and bushes and leaving trees and pylons sticking out.

But there was a stretch of a few miles where the Russians could attempt a crossing. The peat bog was absorbing water like a sponge. Another sluice gate near the village of Chervone was blocking the flow. The Ukrainians tried and failed to destroy it with shelling.

Spotting their opening, the Russians began laying pontoon bridges. Dozens of vehicles came across through channels of water, thick woods and Ukrainian machine-gun positions.

The Ukrainian defenders, including a battalion of the 72nd Brigade and Marik’s special-forces team, withdrew to defensive positions on the edge of the village and the forest, where villagers had used a backhoe to help them dig trenches. The Russians took control of an area filled with cottages that is on the river’s edge in front of the village, where the drone team had fired from on the first day.

Concerned by the Russians’ progress, Gen. Zaluzhniy came to the 72nd Brigade’s command post at the tennis academy in a nearby Kyiv suburb.

“You must stop them here,” Gen. Zaluzhniy told Col. Vdovychenko. “Kyiv is right behind you.”

By then, the Russians had dug trenches in a forest on the village’s northern flank and sought to thrust into central residential areas. Battles raged in the streets and forests around the village. Ukrainian forces later found the bodies of 27 Russians that their comrades had not recovered.

Forced back into the ruins of the village ravaged by artillery strikes, the Ukrainians held firm.

“There was nowhere for us to retreat to,” said Col. Vdovychenko. “If the enemy could have created a bridgehead and regrouped its forces, it would certainly have entered Kyiv.”

But help was at hand. On March 8, sappers had returned to the dam at the mouth of the Irpin River and blown it wide open.

The fresh flow of water overwhelmed the sluice gate at Chervone and rendered the pontoon bridges largely unusable. Marik saw from surveillance drones that Russian vehicles were stranded on the bridges or washed into the river. They couldn’t get them onto the bridges on boggy ground. With no reinforcements able to cross, never mind tanks, the Russian assault petered out.

The Irpin River, said Marik, “changed the direction of the whole war.”

‘They were like rabble’

For the Russian troops under Col. Zakharov, who had died in the yard of a village house, things quickly went awry.

Following the battle, they rammed their vehicles through villagers’ gates and parked them in their yards.

A group returned to Mr. Bobko’s house with some Champagne looted from a foodstore and offered it to his wife as an apology for troubling her with their bloodied and dying commander a day earlier.

“We don’t need it, we have some,” she told them.

“Oh, you have some?” one soldier replied.

The next day, the soldiers returned, asking for alcohol. She gave them a bottle of Champagne and a bottle of cognac to get rid of them.

An hour later, there was a noise outside. One of the soldiers had scaled the brick wall, apparently in search of fresh supplies, and fallen asleep on top.

The occupiers had a brutal streak. They held captives, including the local Orthodox priest, in various cellars across the city. One Russian soldier killed a man and raped his wife, according to Ukrainian prosecutors.

Many of the troops were young men. They would shoot from their tanks a few times in the direction of Ukrainian positions in the morning and a few in the evening, but didn’t try to advance. Instead, they spent their time scrounging cigarettes from locals, arguing over looted goods from stores and stealing items such as sneakers, jeans and a garden trimmer.

“They didn’t look like soldiers,” said Nataliya Landyk, a 67-year-old retiree. “They were like rabble that had just gotten out of jail.”

On the roadside near her house, the Russians dug in a few tanks and covered them with branches. They set up a dining area with beer crates for seats, polishing off bottles of beer, wine and brandy.

Vadym Horbach, the 44-year-old owner of a car-repair yard, asked one officer of around his age what he was doing there.

“I myself don’t know what I’m doing here,” the officer responded. But, he said, he was a military man and had no choice but to follow orders.

The Russians made one more halfhearted effort to advance to Brovary on March 19. As the tanks began firing at the railway bridge where Ms. Chornovol was positioned, she got off a shot that hit the first tank. The rest retreated.

Afterward, the soldiers from the 72nd Brigade and Ms. Chornovol piled into Khutorets, a cafe near the bridge where the cooks would serve them coffee, tea and potato pancakes.

The women had baked a cheese pie, but were refusing to hand it over to Ms. Chornovol’s teammates.

“It’s for the guy who took out the tank,” one of them said.

“It wasn’t a guy,” Ms. Chornovol exclaimed. “It was a gal!”

The Powerlifter

The Russian attacks in the east and west were stalled. The main remaining hope was somehow getting around Kyiv to the south and cutting off the Odessa Highway.

Around the bridge near Makariv, Cat and Greek were going on the offensive. They were outnumbered, which meant they would have to work harder.

The first target was a radio tower deep in the woods. Greek took a team there on foot, leaving a video camera at the top of the tower and setting up observation posts. He tried to leave as much evidence of his presence as possible to trick the Russians into believing that the Ukrainian force was larger than in reality.

There were about 30 of them at that stage, while the Russians numbered hundreds.

In mid-March, Greek decided to go for the dachas where the Russians had dug in. Some were living in basements. They had taken a calf from a nearby field and slaughtered it for meat. Packages of looted food lay everywhere, as well as a few green Russian Army ration packs.

Most of the reconnaissance for Greek’s Group was carried out by a drone pilot who would fly for hours on end sitting on a plastic garden chair with a rug over his legs. He would pause only to charge his vehicle.

Cat’s team of six would speed into position just south of the woods and have their mortar, with an accurate range of around 2 miles, ready to fire in around 15 minutes.

Cat was firing his mortar like a sniper, taking out Russian vehicles and infantry just a few dozen yards away from Greek’s advancing men.

They were moving around and firing in quick bursts, seeking to confuse and startle the enemy in a cold foreign wood.

After around six hours, the Ukrainians pulled back.

Near the end of March, the Russians suddenly launched an assault on the bridge with armored vehicles. The regular Ukrainian troops were wavering.

“Damn, Greek, send a group,” the local commander pleaded with him by phone.

They rushed there and used a machine gun to down a Russian drone, halted four tanks with missiles and called in artillery fire.

They were working round the clock.

“We wanted them to feel like they were in hell and wouldn’t get through,” said Greek. “We didn’t let them rest for a moment. We exhausted them.”

On March 29, they assaulted Russian positions with the help of paratroopers, but lost a tank and suffered casualties, and withdrew.

At night they heard a rumbling sound. The following morning, they were preparing for another assault the drone pilot came with news: “Greek, they are gone.”

Across the whole front around Kyiv, the Russians were pulling back. From Bohdanivka on the eastern flank, from Antonov Airport in the west, and from the far side of the dam in the north.

Cat arrived back from Kyiv where he had gotten his car fixed.

Greek called him and broke the news.

“The f—ers left!” Cat told his group, his voice laced with joy and bitterness. He had wanted to go finish them off.

Aftermath

Marik had been back and forth across the dam and the wrecked bridge in neighboring Demydiv. He would cross at night in the freezing cold with a small team and, guided by locals, ambush Russian positions.

One evening, he had gone to rescue a family that had fled their home and had got lost in the dark on the water-sodden bank. By the time he reached them across the damaged bridge, it was past midnight and one of the children, a young girl, had lost consciousness. He carried her across the bridge and put her in his armored vehicle, covered her in rugs and turned on the heat. Then he went back for her family.

Marik crossed the dam one more time on March 31 after the Russians retreated, pausing to await reinforcements.

He’d done his part to save Kyiv and its people as best he could. He’d acted like a surgeon with a scalpel, making small cuts to drastically change the course of the battle.

“I don’t think one person or another can say they stopped the assault on Kyiv,” he said. “Everyone did.”

Oksana Grytsenko contributed to this article. Maps by Emma Brown.

A beloved mayor and her family helped townspeople resist Russian occupation. They paid for it with their lives. ‘Why were they killed? Because they were Ukrainians’

By James Marson

MOTYZHYN, Ukraine—Mayor Olha Sukhenko took care of her village like a family for more than a decade, locals say, sprucing up public buildings, organizing concerts and settling disputes.

When the Russian army withdrew last week after a monthlong occupation, her neighbors found Ms. Sukhenko’s lifeless body in a shallow grave, her hands bound. Her husband and son lay next to her, dead.

Olha, Ihor and Oleksandr Sukhenko are but three of the faces of the brutal aftermath of Russia’s occupation that Ukrainian officials and villagers say left civilians dead on the street and buried under thin layers of dirt before fierce resistance drove them out.

The 50-year-old mayor held together her central Ukrainian village, cut off and near the fighting at the front. She delivered food and medicine. And she helped the resistance, part of an undercover effort to send Russian troop positions and movements to her country’s military, Ukrainian officials and others involved say.

“She was the best person until her last minute,” said Mykola Kurach, the head of the village’s volunteer defense forces who led the reconnaissance effort.

Residents say the Russian aggression against locals surged as the Russians came under attacks from Ukrainian artillery and ambush teams. The Russians shot two women while hunting for Ukrainian agents, they say. The body of another man, a security guard from the local cottage compound, was found dumped down a well.

“Those are my relatives in that pit,” said Ihor Radchenko, the Sukhenkos’ son-in-law, crouched nearby as local men began to dig the mayor’s family out on Monday. “Why were they killed? Because they were Ukrainians.”

The war came quickly to Motyzhyn, a village of some 1,000 people just off the main highway about 25 miles west of Kyiv. On Feb. 27, three days after Russia invaded, more than 100 Russian army vehicles swept through the quiet, single-lane streets.

“There are foreign bastards in our village,” Ms. Sukhenko posted on her Facebook page on the day they arrived. “Take care. Don’t leave your homes. Keep calm.”

The Russians set up a headquarters at a farm on the northeast edge of the village, digging trenches in the nearby forest where locals hunt for wild mushrooms.

Tetiana Semenova, a friend of Ms. Sukhenko who used to be mayor of the next village, urged her to leave.

“How can I leave people?” she recalls Ms. Sukhenko responding.

In Ukraine, the head of a village is “psychologist, police, priest, and many more things besides,” said Ms. Semenova, now deputy head of the Kyiv regional council. From her small office in the village council, Ms. Sukhenko would sit on her leather chair with a crocheted seat cover, flanked by a map of the village and a flag of Ukraine, adjudicating disputes such as the boundaries of vegetable plots.

Ms. Sukhenko made Motyzhyn “like a flower: pretty, cared for, clean,” said Ms. Semenova. She had the culture center and kindergarten renovated. Every year she put on a concert to celebrate the oldest and youngest in the village, to thank military veterans, and to hand out awards for the best-looking street and building.

Ms. Semenova recalls her friend’s passion for her village at a youth soccer match 15 years ago when she ran up and down the side of the pitch, turning red as she cheered on the village team and throwing her hands in the air when her son, Oleksandr, scored a goal.

“She did everything from the heart,” said Ms. Semenova.

At the start of the war, the population of the village swelled by thousands as many Kyiv residents thought they would be safer in the countryside than the capital. During the Russian occupation with dwindling supplies, many say they relied on food and medication brought personally by Ms. Sukhenko or family members. She arranged deliveries from unoccupied areas and took milk to children in a nearby village. At the start of March, she organized a convoy of civilians to evacuate the town.

Ms. Sukhenko also took on a riskier role: helping pass information on Russian troop locations and movements to the Ukrainian army.

Mr. Kurach, the 43-year-old head of the village’s volunteer defense force, moved in with the Sukhenkos after his house was damaged by shelling. He and Ms. Sukhenko’s husband, Ihor, would head out on scouting missions or “go to work,” as they called it. They and Ms. Sukhenko shared the information with Ukrainian forces via cellphone messages, according Mr. Kurach. Ukrainian army scouts visited the house for updates.

“It is dangerous for everyone, but someone needs to do it,” said Mr. Kurach.

The Russians had dug in on the edge of town in the forest with a network of trenches. Commanders were based in a small farm building nearby, according to local residents, with sacks hung over the windows to block light from getting out and giving away a target. The farm is now strewn with jars of borscht, empty alcohol bottles and juice cartons, and a book in Russian about Nostradamus.

“They were planning to be here for some time,” said Ivan Rudyak, the commander of the territorial-defense unit in a nearby village who is in charge of restoring order in Motyzhyn.

But the assault on Kyiv wasn’t going well. An initial lightning thrust had been repelled. Ukrainian forces had blown bridges and were preventing them from crossing. Attempts to surround the city were proving difficult. One attempt by Russian armored vehicles to break south of Motyzhyn failed, with at least one tank destroyed. Ukrainian artillery shelled Russian positions in the forest on the edge of Motyzhyn.

On March 18, a Ukrainian ambush team sneaked into the village and destroyed a Russian armored vehicle and truck with antitank weapons. The Russians responded with fury. The next day, they launched what they called a clearance operation through the village in search of Ukrainian agents.

Alla Loboda, a 67-year-old resident, was standing outside her front gate just after midday when a Russian armored vehicle flanked by troops with rifles appeared on her street, firing seemingly at random. Neighbors, Alina Sukhenko and her husband, saw her running toward their gate before they hid behind their house. The Russians entered their yard and fired at their car, but left after finding no one there.

The Sukhenkos, distant relatives of the mayor, crept out and saw Ms. Loboda face down by the side of the road, shot through the chest.

Neighbors buried her in her front yard, marking the grave with a wooden cross and a traditional Ukrainian embroidered cloth.

“She was such an elegant lady,” said Alina Sukhenko.

A 42-year-old villager called Yaroslava Litvynenko and her father, Mykola, ran across their yard as the Russians approached. Ms. Litvynenko fell behind, then collapsed to the ground, shot through the chest. The Russians crashed through a fence in an armored vehicle.

“Why were you running?” her father recalled them yelling.

“Why were you shooting?” he countered.

The Russians loaded her into the armored vehicle and took her to their encampment where they tried to save her. She died, and they dug a grave for her, marking it with a wooden cross and a piece of paper with her name on.

Fearful locals hung white flags and wrote “children” on their fences.

The Russians were also closing in on the intelligence operation. Mr. Kurach’s neighbors spotted drones flying over his house. Russian soldiers came and asked where he was.

In the morning on March 23, Ihor Sukhenko, the mayor’s husband, told Mr. Kurach that it was getting too dangerous and that he should leave with his wife and son. Mr. Kurach at first refused, as Ms. Sukhenko said her family would stay. So Mr. Sukhenko turned on the motor of the family car and ordered Mr. Kurach to load his family in and get out.

Minutes later, around midday, the Russians came to the mayor’s house searching for Mr. Kurach. They took Oleksandr Sukhenko’s silver sedan, painting a V on the side, a mark identifying Russian forces.

Ms. Sukhenko called Mr. Kurach’s wife and told her they should run because the Russians were looking for them. By then, the Kurachs were already out of the village on a back road.

The Russian soldiers returned an hour later and took away the mayor and her husband and told Oleksandr that they would bring them back soon. Oleksandr called Mr. Kurach and warned him to destroy his SIM card to prevent the Russians finding and identifying him. In the evening, the Russian soldiers returned and took away Oleksandr.

At the end of March, the Ukrainian army smashed their way into the village to find most of the Russian forces already gone. The Russians appear to have packed up quickly, leaving fatigues and boots at the farm and in the trenches.

There were civilian bodies in the streets and in cars when they arrived, said Mr. Rudyak, the territorial-defense commander who is temporarily in charge of the village.

Some Ukrainian soldiers found the Sukhenkos’ bodies in a shallow grave in the woods, their hands bound and bodies partially visible—a hasty burial. The soldiers scraped back some of the earth and untied their hands.

A fourth person in the grave was an army scout not from the village, residents and police said.

On Monday, police forensic teams arrived to investigate along with a team of men to dig out the bodies.

They hauled the man up who was slumped at the bottom of a well with a bruised and lacerated face and upper body.

Next they dug out Ms. Litvynenko’s body from the nearby grave. Her father glanced into the hole as four men pulled her out.

“Yes,” he said. “It’s her.”

The village is mourning its loss. Alina Sukhenko, who grew up in Motyzhyn, recalled her grandmother saying the Nazis only killed one person when they were in the village.

The Russians “looked for the strongest people,” said Ms. Semenova, Ms. Sukhenko’s friend. “Olha was a locomotive who pulled everyone else behind her.”

“If there is no locomotive, they think we will be slaves like in Russia,” she said. “But we will never be slaves.”

Oksana Grytsenko contributed to this article.

Many citizens thought the occupiers were there to stay. Some fought back, others actively supported them, while the majority just tried to survive.

By Yaroslav Trofimov

SHEVCHENKOVE, Ukraine—When Russian armored columns drove into this rural community of 20,000 people on the first day of the invasion, Mayor Valeriy Prykhodko tried to count the tanks, artillery pieces and fighting vehicles that rolled past his windows.

After the first few hundred, he gave up. “It was too big for counting,” Mr. Prykhodko said. “The horror.”

Located some 35 miles from the Russian border, Shevchenkove fell without a fight the afternoon of Feb. 24. In the six months of Russian rule that followed, many locals came to believe that Moscow, with its awe-inspiring military might, would stay here forever.

Unwilling to work under Russian authority, Mr. Prykhodko tried for a time to resist orders, then fled to Ukrainian-controlled territories. But the municipality’s second-in-command, Executive Secretary Nadiya Sheluh, stayed on the job even once the Russians raised their red-blue-white flag over the building.

Mr. Prykhodko, who is now back in office, recalls being surprised and outraged. But he also acknowledged that many in Shevchenkove think his former colleague did the right thing by helping keep basic services functioning through the occupation. “Our people are split about her,” he said. “Old ladies here say they are thankful to her, that she helped them and fed them.”

Ukrainian forces came back to Shevchenkove in September, as part of their rapid offensive in the eastern Kharkiv region. Now, like other towns and villages in recently liberated parts of Ukraine, Shevchenkove is torn from within by tensions between those who escaped or opposed the Russians—and those who are viewed as having accommodated the enemy.

The delicate task of sorting out one from the other falls on investigators from the Security Service of Ukraine, or SBU, and the National Police, who are collecting evidence in recently retaken territories and in large parts of the country that remain under Moscow’s rule.

In Shevchenkove, a few citizens tried to resist the occupation, scribbling anti-Russian graffiti on walls and passing intelligence to Ukrainian troops. Some others enthusiastically embraced the invaders, taking government positions and joining the Russian-created security forces. The majority in Shevchenkove, as in other occupied areas, tried to survive. As time went by, they were increasingly forced to make compromises with the occupiers, accepting Russian humanitarian aid, pensions or jobs.

At the outset of the war, Ukraine sought to undermine Russia’s hold over occupied areas with strict anti-collaboration laws. Voluntarily joining Russia’s education system on occupied territories can be punished with up to three years’ imprisonment. Taking a managerial role in the Russian-created administrations can mean up to 10 years in prison. Participation in Russian-created law-enforcement and security structures can be punished with up to 15 years behind bars—life imprisonment if it caused the death of a Ukrainian citizen.

Dozens of presumed collaborators have been gunned down by unknown assailants in occupied areas in recent months, mostly in the south of the country. Now that many of the formerly Russian-occupied areas are back under Kyiv’s control here in the east, Ukrainian authorities say they are taking a measured approach.

“We don’t work like the Russians. We don’t keep people in torture chambers,” said Serhiy Bolvinov, head of the investigations department of Ukraine’s National Police in the Kharkiv region. “It’s not enough that someone comes to us and points a finger at someone else to say, ‘This is a collaborator.’ We need to investigate according to the law and to look for solid evidence that will stand up in court.”

In the first month since the Ukrainian offensive reclaimed occupied parts of Kharkiv, he said, law-enforcement agencies opened a total of 132 criminal investigations, with 21 people formally notified of suspicions against them and four others indicted and sent to court.

An SBU investigator in Kharkiv added that rounding up everyone who collaborated with the Russians one way or another would be impossible because of the sheer number of people who broke the Ukrainian law to survive. “In every village here, they tell us that everyone in their own village resisted, but that the next village over is full of collaborators,” the investigator said.

While the Russian-appointed mayor and a few other senior collaborators fled Shevchenkove alongside Russian forces, many others who worked in the occupation administration and education systems, such as Ms. Sheluh, remain here, free to roam the streets after their initial questioning by Ukrainian authorities.

Ms. Sheluh, a former radio broadcaster who speaks flawless literary Ukrainian in a town where most speak either Russian or a mixed dialect known as surzhyk, once unsuccessfully ran for the district legislature on a pro-Western list and showed no pro-Russian inclinations before the war, according to villagers.

Interviewed in her home, Ms. Sheluh said she never accepted pay from the occupiers and worked with the Russians only because she sought to help Shevchenkove’s people in their darkest hour. “I was defending the interests of our local citizens,” she said. “Mostly old people and children stayed here, and they needed the baby formula, the diapers,” she said.

Some in Shevchenkove defend her; others are furious, demanding swift punishment for Ms. Sheluh and anyone else who helped the Russian occupation machine. “Why are our boys dying out there? Why has my grandson not seen his father for seven months? So that we forgive all these people as if nothing had happened?” asked Olha Usyk, a director of one of Shevchenkove’s schools whose son-in-law serves in the Ukrainian military.

Ms. Usyk was especially angry that Ms. Sheluh ordered schools to reopen under Russian authority. Russia has sought to erase Ukrainian identity by teaching in Russian and implementing that country’s curriculum, part of Moscow’s plan to annex the conquered areas.

Speaking at an improvised gathering on Shevchenkove’s leafy main square, Ms. Usyk and other educators complained that the returning Ukrainian authorities were slow to weed out Russian collaborators. “What’s scary is that, on the front line, it’s clear who is the enemy. But here, it’s murky, a real swamp,” said Maria Danylova, a teacher. “Everyone who collaborated with the Russians here was making their own choices. Nobody put guns to their heads.”

In the first days of Russian occupation, Shevchenkove—named after Ukraine’s national poet who spent a decade in penal exile for his opposition to Russian imperial rule—was largely left alone.

Still, residents faced wrenching decisions. Serhiy Kovshar, a former police lieutenant whose son was killed fighting Russian proxies in the Donbas region in 2015, quietly removed a commemorative plaque on the front of his house. By May, he had joined the new occupation police force, say local residents who saw him at checkpoints and on patrols.

At the community’s 73-bed hospital, Russian soldiers arrived with one of their men, with an inflamed appendix, and demanded at gunpoint that doctors operate on him, said Natalia Nesvoyeva, who served as acting director. The surgery was successful, she said.

Over the course of the occupation, more than 100 Russian soldiers ended up at the Shevchenkove hospital, usually for conditions that weren’t life-threatening, according to Ms. Nesvoyeva. “They had shot themselves in the foot, or had hypertension crises after an overdose of something, or frostbite,” she said.

Ukrainian officials say that providing urgent medical care to Russian soldiers is protected under international humanitarian law and thus isn’t considered collaboration.

Meanwhile, Mayor Prykhodko and other local officials worked on their own to try to secure supplies, bake bread, and keep basic services running.

On March 5, agitated Russian soldiers arrived at Mr. Prykhodko’s office in the two-story government headquarters on Shevchenkove’s main square, he said. As soldiers pointed guns at the mayor, their commander demanded that he hand over lists of locals who served in the military, particularly the Donbas, that he take down the Ukrainian flag that still flew over the municipality, and that he write a letter to Vladimir Putin welcoming the Russian takeover.

“I will throw a hand grenade if you don’t,” the Russian officer threatened. Mr. Prykhodko, surrounded by some 15 staff members, decided the threat was empty and stood his ground. The Russians ended up driving away and the Ukrainian flag kept flying.

Initially, Russia’s presence in Shevchenkove mostly consisted of ill-equipped troops from the Russian-controlled statelets of Donbas. They demanded that Mr. Prykhodko allocate them housing. When he refused, he said, they settled in vacant homes and started looting. “They said they have been ordered to operate in a self-reliant fashion,” Mr. Prykhodko said. “They were dirty and stinky. We knew they just drank all night, and didn’t do much else.”

By April 18, a new batch of disheveled, shellshocked Russian troops arrived here, redeployed after the Russian withdrawal from Kyiv. “If you had forgotten about Irpin and Bucha, we will remind you,” they shouted, referring to the massacre of Ukrainian civilians in those suburbs of Kyiv. There were no massacres in Shevchenkove, however.

Ms. Danylova, a teacher of Ukrainian and one of the most passionate pro-Ukrainian activists in Shevchenkove, had spent the previous four decades collecting artifacts for the museum of Ukrainian traditional culture that was housed in the local high school.

Having heard about how the Russians burned a museum containing the paintings of naïve-style folk artist Maria Prymachenko near Kyiv, she decided to rescue the century-old embroidered towels, shirts and wedding dresses and hid them in her cellar and in friends’ homes. To do so, Ms. Danylova and her son, Ruslan Shokirov, had to brave Russian checkpoints.

“There is no doubt that they would have destroyed these items if they had caught us—they were burning everything Ukrainian. The only question is what they would have done to us,” Mr. Shokirov said. All the artifacts survived.

On April 27, a different kind of Russian security force, well-equipped and in modern vehicles, arrived at the Shevchenkove municipality. “Run away, they are hunting for you,” Mr. Prykhodko said he was told by colleagues. He jumped on his bicycle and waited out the night in the dark behind the outhouse at his brother’s home. The Russians spread word they wanted him to start working under their authority.

“All they want is for you to open the doors of the municipality and distribute their humanitarian aid. What’s wrong with that? They won’t do anything to you,” Mr. Prykhodko said he was told by a local woman who spoke with the Russians. “Are you crazy? I am a Ukrainian village mayor, not a Russian one,” he said he retorted. Unwilling to collaborate, Mr. Prykhodko fled Shevchenkove the following day and made his way through the front lines to Ukrainian government-controlled territory.

In his place, the Russians installed a local horse breeder, Andrey Stryzhko, who never hid his sympathies for Moscow. Usually dressed in black and wearing the papakha woolen hat of Russian Cossacks, Mr. Stryzhko used to hang the red Soviet flag outside his home even before the war. One of his first steps was to have himself filmed stripping away the Ukrainian coat of arms on Shevchenkove’s main square. He also ordered the removal of a monument to Ukrainian veterans of the war in Donbas.

Unlike Mr. Prykhodko, Ms. Sheluh, the community’s second-in-command, remained on her job. She played down her contact with the Russians. “I was in my office downstairs and they and their authority was upstairs,” she said. “I just worked in my own place.”

Ms. Sheluh sat in on meetings with the new Russian authorities. Some were filmed for Russian propaganda channels. Mr. Prykhodko said he terminated Ms. Sheluh’s employment and stopped her Ukrainian salary payments once he learned about her work with the Russians.

While most Shevchenkove police withdrew to government-held areas in February, some officers joined the new Russian-run force that detained curfew breakers and put them to work sweeping streets and picking weeds. The villagers learned a new verb—“to kadyrov”—which meant beating inmates with a large wooden pole, a practice introduced by troops loyal to Chechen strongman Ramzan Kadyrov, a key Putin ally.

“It was a bad time. I was afraid to walk on the street alone,” said Yana Holoboyko, a high-school student. “The Russians were very aggressive, especially when they got drunk, driving around and picking up women.”

On Ukraine’s constitution day in late June, block-length graffiti appeared on one of Shevchenkove’s streets. “Shevchenkove is Ukraine. Death to occupiers. Stryzhko—you’ll kick the bucket,” it said. Nobody bothered to paint it over.

Around the same time, Aleksandr Sidyakin, head of the executive committee of Russia’s ruling party, came to nearby Kupyansk to announce that locals could now start receiving Russian passports. “Russia is here for eternity!” he proclaimed to applause.

In the Shevchenkove hospital, doctors and nurses did what they could, treating civilians and Russian soldiers alike. “The Russians always came here with guns. We were afraid of them, and they were afraid of us. You never knew what they could do,” said the head nurse, Olha Kokhan.

Unlike in Kupyansk, where most hospital staff quickly switched to a Russian contract with its significantly higher pay, the doctors and nurses in Shevchenkove continued to receive Ukrainian salaries in their bank accounts.

With no Ukrainian banks functioning in occupied areas, they could only withdraw cash, at a commission of as high as 35%, via entrepreneurial middlemen from the Donbas who arrived with an internet hot spot that allowed online bank transfers.

Gradually, pressure to work with the Russians became hard to resist. A few of the female staff started dating Russian soldiers and officers. Vitaliy Ganchev, head of the Russian-created interim administration of the Kharkiv region, and other officials came to Shevchenkove on Aug. 23 to meet with the hospital staff, telling them that there was no point in holding out.

“You still hope the Ukrainians will come back? No, they will never come back,” Ms. Kokhan, the nurse, said Mr. Ganchev told them.

Russia paid more attention to schools. The occupation administration’s building in Kupyansk is still packed to the brim with Russian textbooks, teaching aids and educational posters. Ukrainian books and materials were removed and destroyed.

In August, Ms. Sheluh, the Shevchenkove executive secretary, called schoolteachers and directors, as well as the staff of the local kindergarten, demanding they reopen their institutions on Sept. 1. While all the school directors refused, Oksana Simutina, the local kindergarten director, agreed.

The kindergarten staff spent two weeks cleaning up the facility that was closed since February, washing curtains and sheets, sweeping the floors, and culling waist-high weeds, she said. Some 20 children showed up on Sept. 1. “There can be no politics in a kindergarten. We never communicated with the Russians,” said Ms. Simutina.

Out of the community’s 288 schoolteachers, only about one-tenth showed up as classes started on Sept. 1, according to Mr. Prykhodko, the mayor.

Teacher Ludmyla Zdorovko said Russian-appointed officials in Shevchenkove told her, “Go to work or you will remain jobless forever.” She added, “The people who went to work for them, it was not because they believed in the Russian world. Not many people did here. They were greedy and just wanted money.”

Ms. Sheluh said no Ukrainian books were destroyed in the community’s schools, and no Russian symbols displayed. Her decision was driven by patriotism, she said. “I asked our teachers to go to work and teach the Ukrainian language because I didn’t want them to bring outsiders to schools,” she said. “This is our land, we all grew up here, and nobody can educate better than our own people.”

On Sept. 5, senior staff of the Shevchenkove hospital were summoned to Kupyansk for a meeting with the occupation administration. “They asked that we collaborate and told us that we have no other choice,” Ms. Kokhan said. “And we almost agreed. Six months had gone by. It’s a very long time.”

If they had signed on to the Russian health system, as they planned to do days later, they would have been considered collaborators under Ukrainian law. But the following day, the Ukrainian offensive in the Kharkiv region began.

Russian soldiers disappeared from Shevchenkove’s hospital before dawn. Then, a few hours later, on Sept. 7, Ukrainian forces showed up on the street outside. “You can’t even imagine the joy, the euphoria we all felt when we walked out and suddenly saw that finally our boys are back here, with our flags, right outside,” said the acting hospital director, Ms. Nesvoyeva.

Unlike Kupyansk, severely damaged in fighting, Shevchenkove survived the occupation largely intact and with few casualties. Mr. Stryzhko, the Russian-appointed mayor, and a handful of other Russian-appointed officials escaped with the last Russian troops. Many other Russian sympathizers remain.

“There are still people here in town who wait for the Russians to return,” said Yulia Fedorova, a paramedic in the hospital. “I have one in my own building. I tell her—if you like them so much, why are you lining up for Ukrainian humanitarian aid on the square instead of running away to your Russia?”

Soon after the Russian retreat, Mr. Prykhodko returned to his duties in the municipality. Ukrainian security authorities set up an office, too, looking for collaborators.

Mr. Kovshar, the former policeman, was detained for a couple of hours, and then released. Interviewed in his home, he acknowledged that he briefly joined the Russian-led police but said he did it only to steal the list of local hunters who owned rifles, so that the Russians wouldn’t have it. He said he passed intelligence to Ukrainian forces all along. The plaque commemorating his son’s heroism in Donbas is now affixed again on his home, a Ukrainian flag flying above it.

Queried about the case, Ukrainian law-enforcement officials declined to comment on individual investigations. Mr. Prykhodko, the mayor, said there was no legally admissible evidence of collaboration by Mr. Kovshar.

Ms. Sheluh, the municipality secretary, said she was repeatedly interrogated, her phone and her passport taken away. She remains in her home in Shevchenkove, waiting to see how the inquiry progresses. Ms. Simutina, the kindergarten director, is free after her three interviews with the SBU. “I don’t believe we were collaborators,” she said, speaking as she was running errands in central Shevchenkove. “We worked in our own village, for our own people and for our own children.”

In the Shevchenkove hospital, the staffers who dated Russian soldiers remain on their jobs, even though many colleagues no longer socialize with them. “They wanted to fix their personal lives, but chose the wrong men. Now, they are despised by the entire staff,” said Ms. Nesvoyeva. “They are good workers, and I cannot fire them. But they are crying all day that other people have a bad attitude to them. What else did they expect?”

By Yaroslav Trofimov

KHARKIV, Ukraine—A dazed older woman picked her way through Kharkiv’s central Constitution Square, navigating a blasted landscape strewn with twisted metal, glass shards and fragments of brick.

Russian missile strikes have gutted every one of the elegant 19th-century buildings lining the street. The innards of fashion boutiques, with decapitated mannequins, spilled onto the sidewalk. A cocktail bar down the road, its windows blown out, had bottles of Campari, gin and vermouth on display, untouched.

“Have you seen PrivatBank?” the woman asked a rare passerby. The ATM there had eaten her debit card, she said. “Have you? I need to get the card back, for my pension.” The bank building had been reduced to a jumble of broken glass and crumpled metal. Its security alarm still blared.

In the days since Russian President Vladimir Putin launched his invasion of Ukraine on Feb. 24, shelling and airstrikes have killed hundreds of people in Kharkiv, a city of 1.4 million about 20 miles from the Russian border. Residents spend their days and nights huddled in the subway. Above them, explosions devastate their city.

At least 400 high-rise apartment buildings have been hit, Kharkiv city authorities said. Strikes have damaged the art museum, with its collection of famous Russian painters including Repin and Shishkin, and the Korolenko library, which houses priceless manuscripts.

“Everyone is in shock here,” said Ihor Terekhov, the city mayor. “We used to think of the Russians as our brothers. Even in our worst nightmares, we never imagined that they would destroy our city.”

Russia’s attempt to use rapid thrusts by armored columns and assaults by paratroopers and special forces to seize the Ukrainian capital of Kyiv and other cities, overthrowing the country’s government, has stalled in the face of fierce resistance. Now, Moscow is resorting to a punishing, wholesale destruction, shelling and bombing residential neighborhoods and historic downtowns.

Kharkiv has been pulverized with particular cruelty, even though almost all of its citizens are Russian-speakers, many of whom felt affinity with Russia in the past.

On Friday, the thumps of artillery punctured the city’s eerie silence. Few people were on the street. Around the corner from Constitution Square, the new Nikolsky shopping mall—complete with an oyster bar and virtual-reality game zone—smoldered. A Russian missile had plunged through its roof Wednesday night.

On the streets, police patrols watch for any looting. Municipal crews used a break in the shelling to repair power and water lines. Several Kharkiv taxi drivers worked together to remove debris from Constitution Square.

“There isn’t much work nowadays, so we’ve come here to clean up the city and raise morale,” said Andriy Kolesnik, one of the drivers. “We can do it, so we do it.”

It will take generations for the people of Kharkiv to forgive Russia and the Russians, said Mr. Terekhov, the mayor, as he visited a subway station-turned-dormitory. People there asked to take selfies with him.

“The Russians thought, mistakenly, that Kharkiv would greet them with open arms,” Mr. Terekhov said. “But nobody wants the Russians here, nobody has invited them here. Our people are fighting them for our freedom, for the future of our children.”

Misguided mission

Back in 2014, in the wake of Kyiv street protests that ousted pro-Russian Ukrainian President Viktor Yanukovych, sympathy for Russia ran high in Kharkiv. Moscow-backed protesters briefly took over the regional government, hoisting a Russian flag and proclaiming a so-called Kharkiv People’s Republic, along the lines of similar pro-Russian statelets in nearby Donetsk and Luhansk.

The desolate record of Russian rule in Donetsk and Luhansk, however, has changed local minds, especially after more than 100,000 refugees from Donetsk moved to the city, bringing tales of expropriations, murders and political repression.

That shift wasn’t necessarily taken into account by Russia’s military planners, whose strategy in Kharkiv can only be explained by a profound miscalculation of the city’s mood, Ukrainian officers said. In the first days of the war, several units of lightly armed Russian troops in Tigr infantry vehicles penetrated deep into Kharkiv. Within hours, they were all killed or captured.

“I don’t know what they were hoping for. To seize the regional government building right away?” said Ukrainian air force Maj. Oleh Koshevyi, who serves at the Kharkiv-based Ukrainian Air Force University. “Instead, everyone has united against them.”

Responding to that initial assault, Ukraine pulled fresh troops into the city, organizing a defense around its northern, western and eastern perimeters that has been holding ever since. While Russian forces are close enough to shell residential neighborhoods with Grad multiple-launch rocket systems and artillery, they haven’t been able to advance and, in many areas, have been pushed back.

The roads from Kharkiv to the Ukrainian cities of Poltava and Dnipro remain open, allowing resupplies of food, fuel and ammunition, as well as providing a way out for civilians who have somewhere to go.

“The first days were scary. There was confusion, it was unclear who was where in the city,” said Lt. Andriy Babak of the Ukrainian Army’s 92nd Brigade, which is defending Kharkiv. “Now we have established the lines of defense and keep repelling their attacks.”

Frustrated with its inability to enter or encircle the city, Russia pivoted to the new strategy of destruction here on March 1, the end of the war’s first week.

At 8 that morning, a Russian ballistic missile slammed into Kharkiv’s Freedom Square, just outside the regional administration headquarters, a Stalin-era neoclassical building that pro-Russian protesters had taken over in 2014. Several other missile strikes since then have turned entire downtown city blocks into a cityscape of destruction akin to Stalingrad, Aleppo or Grozny.

Burned-out, shrapnel-peppered cars, the remains of their occupants melted into the seats, dot the streets. Twisted pieces of roofing hang from electricity lines. Inside the regional administration’s courtyard, a giant crater marked the spot where a Russian missile vaporized an ambulance.

A rigid, frozen body is still lying outside. In the governor’s former office, a book on the challenges and perspective of Ukrainian law studies remains, pristine, amid the soot and debris. Elsewhere in the building, pieces of flesh spatter whitewashed walls.

Oleh Supereka, a former studio portrait photographer turned soldier, pointed to a fifth-floor apartment of a gutted building near the regional government building. His friend lived there, he said, and miraculously survived the blast, which sheared off the living room’s outer wall.

“The Russians are doing this out of desperation,” Mr. Supereka said. “They understand they can’t take the city from the land, so they just destroy it from the air.”

The initial bombing of Freedom Square was one of many Russian strikes on Kharkiv that day. At around 10:30 p.m., four Russian cruise missiles slammed into the compound of the Kharkiv Air Force University. One of them hit a residential building that housed retired officers and the families of current officers. Most active-duty personnel were by then deployed to the front lines around Kharkiv, and so women and children made up most of the dozens of victims buried under the rubble that night, said Lt. Col. Oleh Pechelulko, the university’s deputy commander.

A mother lost

Ten days later, rescue crews were still digging through the crumbled building. Col. Pechelulko said his wife luckily had left their apartment there a few hours earlier. “Everything has burned down. Nothing is left. Not memories. Not documents. Nothing. I am continuing the war just with what I had on my back that night,” he said, showing the charred block where the couple once lived.

The remains of a playground stood amid the debris. A painting of a lion with a pink mane, part of a mural, still showed on a charred brick wall. Wrecked cars littered the space.

“All the men had gone off to fight and defend Kharkiv that night,” Col. Pechelulko said. “Now, every one of them will avenge his family, his murdered children, his murdered wife. We will never forgive the enemy for this.”

At 3:30 p.m. on March 7, Serhiy and Elena Kosyanov’s children were lying on a sofa and playing with smartphones in northern Kharkiv’s Saltivka neighborhood. Elena, a kindergarten teacher, was in the kitchen and her mother was preparing to walk their dog. Serhiy was opening the door to their apartment building downstairs. He was in good spirits: After two hours waiting in line, he had filled their car with gas.

Then a Russian projectile slammed through their living room window and exploded. The building caught fire. One of the shards pierced the face of the couple’s 8-year-old son, Dmitri, and lodged between the base of his skull and his spine. The boy remains in the intensive-care unit of Kharkiv’s Hospital Number 4, fighting for his life. His sister suffered burns, and his grandmother got a concussion and broken ribs.

“I came home just a little bit too late because of the wait at the gas station. We were supposed to leave Kharkiv that day,” Serhiy said, standing outside the hospital’s intensive-care unit. “All our pets have burned alive. Two cats. One dog. One hamster,” his wife said.

Seven-year-old Vladimir Baklanov was in the same hospital, recovering from gunshot wounds. As the boy and his mother tried to flee Kharkiv by car, they were caught in a crossfire between Russian and Ukrainian forces on Feb. 28, four days after the invasion. His mother died.

Vladimir’s father, Stanislav, a manager at a construction company, was on assignment in Uzbekistan when the war erupted. He has since returned to Kharkiv, and spends his days and nights in the hospital. Stanislav closed the door so Vladimir wouldn’t hear his conversation with The Wall Street Journal.

“He probably knows that his mama is dead,” Stanislav said. “But he still keeps calling her.”

The hospital’s chief neurosurgeon, Oleksandr Dukhovskyy, was supposed to be attending a conference in Bogotá, Colombia, this weekend. He hasn’t left the hospital since Feb. 24, except for a handful of one-hour forays home.

“It’s a war, and it’s a dirty war,” Dr. Dukhovskyy said, showing X-rays and CT scans of injuries to his pediatric patients from Russian shelling. “People who do this cannot be human. Those are war crimes, and one day these people must be put on trial.”

In hiding

Unlike in Kyiv, where Ukraine has concentrated its meager air defenses and can shoot down many incoming missiles, Kharkiv has limited means apart from shoulder-fired missiles to counter Russia’s air superiority. All the Ukrainian military airfields nearby were knocked out in the early hours of the war. While snowy, cloudy weather has favored Ukrainian defenders in recent days, the war has been mostly conducted in stealth, rapid movements of small Ukrainian units that hunt Russian armor, artillery and rocket launchers.

“Many of their resupply columns have been destroyed, and they have a big problem with fuel and food. So they loot from the local villagers and take their homes,” Lt. Babak said. “As for us, we receive information from the locals all the time, and we try to move ahead and hit the Russians little by little.” A stock of British-supplied antitank missiles was at his unit’s disposal. On Thursday, one was used to destroy a Russian armored vehicle, he said.

Support from local residents has also helped soldiers like Private Andriy Tkachuk. His company in the 92nd Brigade, deployed near the border with Russia northeast of Kharkiv, disintegrated after suffering heavy combat casualties in the first days of the war.

Pvt. Tkachuk and eight fellow soldiers hiked to a nearby village, where they hid their weapons and, with the help of local residents who have fed and housed them, changed into civilian clothes. After days of dodging Russian patrols, they made their way through a forest to link up with Ukrainian police, he said, at one of the brigade’s improvised bases in Kharkiv. A steady flow of civilian volunteers bring fresh-baked flatbread, juices and soup.

In the shelters of Kharkiv’s underground subway, other volunteers have set up an improvised pharmacy and library, as well as a travel desk helping to coordinate the departure of civilians to western Ukraine. Books spanned Harry Potter, the Chronicles of Narnia and those by Russian writer Mikhail Bulgakov.

At night, mothers pushed baby carriages along the platform decorated with billboards of the Chelsea Football Club, lulling their little ones to sleep. An entire wall was covered with drawings made by children inside the station. One picture, by 7-year-old Illarion, was of his poodle Adele. “We all want peace,” it said. “My Adele also wants peace.”

Neighbors brought down a microwave, a refrigerator and an espresso machine. Lawyer Roman Cherepakha, one of the volunteers, made Americano coffee drinks. “We will win because the righteous always win in the end,” he said. “And in the meantime, I am here to help people get through this.”

Mr. Terekhov, the mayor, was equally certain of a Ukrainian victory. “We will never surrender,” he said. “But now, the main task is to make sure our people stay alive.”

In the two-day battle of Voznesensk, local volunteers and the military repelled the invaders, who fled leaving behind armor and dead soldiers

By Yaroslav Trofimov

VOZNESENSK, Ukraine—A Kalashnikov rifle slung over his shoulder, Voznesensk’s funeral director, Mykhailo Sokurenko, spent this Tuesday driving through fields and forests, picking up dead Russian soldiers and taking them to a freezer railway car piled with Russian bodies—the casualties of one of the most comprehensive routs President Vladimir Putin’s forces have suffered since he ordered the invasion of Ukraine.

A rapid Russian advance into the strategic southern town of 35,000 people, a gateway to a Ukrainian nuclear power station and pathway to attack Odessa from the back, would have showcased the Russian military’s abilities and severed Ukraine’s key communications lines.

Instead, the two-day battle of Voznesensk, details of which are only now emerging, turned decisively against the Russians. Judging from the destroyed and abandoned armor, Ukrainian forces, which comprised local volunteers and the professional military, eliminated most of a Russian battalion tactical group on March 2 and 3.

The Ukrainian defenders’ performance against a much-better-armed enemy in an overwhelmingly Russian-speaking region was successful in part because of widespread popular support for the Ukrainian cause—one reason the Russian invasion across the country has failed to achieve its principal goals so far. Ukraine on Wednesday said it was launching a counteroffensive on several fronts.

“Everyone is united against the common enemy,” said Voznesensk’s 32-year-old mayor, Yevheni Velichko, a former real-estate developer turned wartime commander, who, like other local officials, moves around with a gun. “We are defending our own land. We are at home.”

The Russian military says its Ukraine offensive is developing successfully and according to plan. Moscow hasn’t released updated casualty figures since acknowledging on March 2 the death of 498 troops, before the Voznesensk battle.

Russian survivors of the Voznesensk battle left behind nearly 30 of their 43 vehicles—tanks, armored personnel carriers, multiple-rocket launchers, trucks—as well as a downed Mi-24 attack helicopter, according to Ukrainian officials in the city. The helicopter’s remnants and some pieces of burned-out Russian armor were still scattered around Voznesensk on Tuesday.

Russian forces retreated more than 40 miles to the southeast, where other Ukrainian units have continued pounding them. Some dispersed in nearby forests, where local officials said 10 soldiers have been captured.

“We didn’t have a single tank against them, just rocket-propelled grenades, Javelin missiles and the help of artillery,” said Vadym, commander of the Ukrainian special-forces reconnaissance group in the area and a Voznesensk resident. “The Russians didn’t expect us to be so strong. It was a surprise for them. If they had taken Voznesensk, they would have cut off the whole south of Ukraine.”

Ukrainian officers estimated that some 100 Russian troops died in Voznesensk, including those whose bodies were taken by retreating Russian troops or burned inside carbonized vehicles. As of Tuesday, 11 dead Russian soldiers were in the railway car turned morgue, with search parties looking for other bodies in nearby forests. Villagers buried some others.

“Sometimes, I wish I could put these bodies on a plane and drop them all onto Moscow, so they realize what is happening here,” said Mr. Sokurenko, the funeral director, as he put Tuesday’s fifth Russian cadaver on blue-plastic sheeting inside his van marked “Cargo 200”—Soviet military slang for killed in action. A Ukrainian military explosives specialist accompanied him, because some bodies had been booby trapped.

About 10 Ukrainian civilians died in Voznesensk during the combat and two more after hitting a land mine afterward, local officials said. Ukraine doesn’t disclose its military losses. There were fatalities, mostly among the Territorial Defense volunteer forces, local residents said.

The Russian operation to seize Voznesensk, 20 miles from the South Ukrainian Nuclear Power Plant, was ambitious and well-equipped. It began after Russian forces fanned out of the Crimean Peninsula, which Moscow severed from Ukraine and annexed in 2014, and thrust northward to seize the regional capital of Kherson on March 1. They pushed to the edge of Mykolaiv, the last major city before Odessa, Ukraine’s main port.

About 55 miles north of Mykolaiv, Voznesensk offered an alternative bridge over the Southern Bug river and access to the main highway linking Odessa with the rest of Ukraine. Russian forces raced toward the town at the same time as they made a successful push northeast to seize the city of Enerhodar, where another major Ukrainian nuclear power plant is located. Voznesensk’s fall would have made defending the nuclear plant to the north of here nearly impossible, military officials said.

Mayor Velichko worked with local businessmen to dig up the shores of the Mertvovod river that cuts through town so armored personnel vehicles couldn’t ford it. He got other businessmen who owned a quarry and a construction company to block off most streets to channel the Russian column into areas that would be easier to hit with artillery.

Ahead of the Russian advance, military engineers blew up the bridge over the Mertvovod and a railroad bridge on the town’s edge. Waiting for the Russians in and around Voznesensk were Ukrainian regular army troops and members of the Territorial Defense force, which Ukraine established in January, recruiting and arming volunteers to help protect local communities. Local witnesses, officials and Ukrainian combat participants recounted what happened next.

Missile strikes

The Russian assault began with missile strikes and shelling that hit central Voznesensk, destroying the municipal swimming pool and damaging high-rises. Helicopters dropped Russian air-assault troops in a forested ridge southwest of Voznesensk, as an armored column drove from the southeast. Mr. Velichko said a local collaborator with the Russians, a woman driving a Hyundai SUV, showed the Russian column a way through back roads.

Ukrainian officers estimate that some 400 Russian troops took part in the attack. The number would have been bigger if these forces—mostly from the 126th naval infantry brigade based in Perevalnoye, Crimea, according to seized documents—hadn’t come under heavy shelling along the way.

Natalia Horchuk, a 25-year-old mother of three, said Russian soldiers appeared in her garden in the village of Rakove in the Voznesensk municipality early March 2. They told her and neighbors to leave for their safety, and parked four tanks and infantry fighting vehicles between the houses. “Do you have anywhere to go?” she recalled them asking. “This place will be hit.”

“We can hide in the cellar,” she replied.

“The cellar won’t help you,” they told her. Hiding valuables, she and her family fled, as did most neighbors.

Outside Rakove, Volodymyr Kichuk, a guard at a walnut plantation, woke to find five Russian airborne troops in his hut. They took his phone and forced him to lie on the ground, said his wife, Hanna. “Once they realized there was nothing to steal, they told him: You can get up after we leave,” she said. By day’s end, the couple were gone from the village.

Russian soldiers took over villagers’ homes in Rakove and created a sniper position on a roof. They looked for sacks to fill with soil for fortifications, burned hay to create a smoke screen and demanded food.

A local woman who agreed to cook for the Russians is now under investigation, said Vadym. “A traitor—she did it for money,” he said. “I don’t think the village will forgive her and let her live here.”

Downhill from Rakove, Russian forces set up base at a gas station at Voznesensk’s entrance. A Russian BTR infantry fighting vehicle drove up to the blown-up bridge over the Mertvovod, opening fire on the Territorial Defense base to the left. Five tanks, supported by a BTR, drove to a wheat field overlooking Voznesensk.

A group of Territorial Defense volunteers armed with Kalashnikovs was hiding in a building at that field’s edge. They didn’t have much of a chance against the BTR’s large-caliber machine gun, said Mykola, one of the city’s Territorial Defense officers; some were killed, others escaped. Russian troops in two Ural trucks were preparing to assemble and set up 120mm mortars on the wheat field, but they got only as far as unloading the ammunition before Ukrainian shelling began.

Phoning in coordinates

As darkness fell March 2, Mykola, who owns a company transporting gravel and sand, took cover in a grove on the wheat field’s edge under pouring rain. The Russian tanks there would fire into Voznesensk and immediately drive a few hundred yards away to escape return fire, he said.

Mykola was on the phone with a Ukrainian artillery unit. Sending coordinates via the Viber social-messaging app, he directed artillery fire at the Russians. So did other local Territorial Defense volunteers around the city. “Everyone helped,” he said. “Everyone shared the information.”

Ukrainian shelling blew craters in the field, and some Russian vehicles sustained direct hits. Other Ukrainian regular troops and Territorial Defense forces moved toward Russian positions on foot, hitting vehicles with U.S.-supplied Javelin missiles. As Russian armor caught fire—including three of the five tanks in the wheat field—soldiers abandoned functioning vehicles and escaped on foot or sped off in the BTRs that still had fuel. They left crates of ammunition.

Mykola picked up a Russian conscript days later, he said, who served as an assistant artillery specialist at a Grad multiple-rocket launcher that attacked Voznesensk from a forest. The 18-year-old conscript, originally from eastern Ukraine and a Crimea resident since 2014, suffered a concussion after a Ukrainian shell hit near him. He woke the next morning, left his weapon and wandered into a village, Mykola said. There, a woman took him into her home and called the village head, who informed Territorial Defense. “He’s still in shock about what happened to him,” Mykola said.

Vadym, the reconnaissance-unit commander, said he captured several soldiers in their early 20s and a 31-year-old senior lieutenant from the Russian military intelligence. The lieutenant, he said, had forced a private to swap uniforms but was discovered because of the age discrepancy—and because Ukrainian forces found Russian personnel files in the column’s command vehicle.

“The Russians had orders to come in, seize, and await further instructions,” Vadym said. “But they had no orders for what to do if they are defeated. That, they didn’t plan for.”

Russian troops had detained a local man on March 2 after they found him to have binoculars, villagers said. “They had put him in a cellar and told him they will execute him in the morning, for correcting artillery fire,” Vadym said, adding that the detainee wasn’t a spotter. “But in the morning they didn’t have time to execute him. They were too busy fleeing.”

The Russians retreat

As the Russian forces retreated on March 3, they shelled the downhill part of Rakove. A direct hit pierced the roof of the local clinic, where Vadym’s mother, Raisa, worked as a nurse. “We’ve just built a new roof,” she sighed, showing the gaping hole. “But it doesn’t matter. The main thing is that we have kicked them out, and survived.”

When villagers returned to Rakove on March 4, they found their homes ransacked. “Blankets, cutlery, all gone. Lard, milk, cheese, also gone,” said Ms. Horchuk. “They didn’t take the potatoes because they didn’t have time to cook.”

This week, village homes still bore traces of Russian soldiers. Cupboards and closets were still flung open from looting, and Russian military rations and half-eaten jars of pickles and preserves littered floors.

The Ukrainian army’s 80th brigade was towing away the last remaining Russian BTRs with “Z” painted on their sides, the identification markers that in Russia have become the symbol of the invasion. About 15 Russian tanks and other vehicles were in working or salvageable condition, said Vadym. “We are ready to hit the Russians with their own weapons,” he said. Others, mostly burned-out wrecks, were removed from streets because they scared civilians and contained ordnance, the mayor said.

Electricity, disrupted during combat, has returned in Voznesensk, as have internet, gas and water services. ATMs have been restocked with cash, supermarkets with food.

The only explosions are from bomb squads occasionally disposing ordnance. Mr. Velichko, the mayor, fielded citizen phone calls Tuesday, telling one he would take care of a possibly rabid dog and assuring another that her utilities wouldn’t be cut in wartime even if she was late in paying. He argued with an army commander because Ukrainian soldiers had siphoned fuel from the gas station.

Spartak Hukasian, head of the Voznesensk district council, said the city—no longer near front lines—was starting to get used to relatively peaceful life again. “He who laughs last laughs best,” he said. “We haven’t had a chance to laugh until now.”

Corrections & Amplifications

After publication, the Journal removed the surnames of some people mentioned in this article. (March 18.)