A Decade at War: How Putin’s Invasions Set the Course for One Ukrainian Soldier

When I first met Dudnik in 2014, he was still a teenager, sitting broodily atop his armored vehicle as curious civilians peppered him with questions and Russian troops hovered a few miles away across the border. He warned that if Russia picked a fight, “we’ll respond, and it won’t be pretty."

The contours of Dudnik’s life have been shaped by Ukraine’s bloody decade under assault from Russia. Now a sergeant, he sports a beard, bears a few lines on his face and winces at loud music following several concussions. He is a survivor of the brutal fighting around Bakhmut in which thousands of troops from each side were killed. He gained national prominence last year when he shot down a Russian warplane with a shoulder-fired missile, and I got back in touch.

Dudnik has seen Russian soldiers kill comrades an arm’s length away and devastate parts of Ukraine but still fail to subdue it. His father and brother, who also fought in 2014, have been injured and can no longer fight. Now, he is worried that waning support from the U.S. is handing Russia an advantage in ammunition that is hard to counter.

But Dudnik says he is determined to keep fighting—so his 6-year-old son won’t have to. “We need to drive them out so that the next generation doesn’t have to fight," he said.

Dudnik was born in a village in southeastern Ukraine and named for his mom’s favorite actor, Alain Delon. His interest in the military was spurred by something which, years later, might seem odd: Russian propaganda films about the war in Chechnya.

“Back then we were zombified," he said.

A few months after enlisting in 2014, he was deployed with the 25th Airborne Brigade to the border in March as Russia gathered troops around Ukraine and threatened to invade as it pursued its annexation of Ukraine’s Crimea peninsula.

At first, it was difficult to process for Dudnik, who like most had never expected to fight against Russia. “It’s hard to imagine war against our brothers," he said at the time.

That earlier affinity for Russia is long gone.

“We are on our land and we have to defend it," he said recently. “We don’t need Russian boots on our land."

Looking back, Dudnik says that Ukraine would likely have been overwhelmed if the Russians had invaded in the same numbers in 2014 as it did in 2022. Ukraine could muster only a few thousand combat-ready troops and its military inventories had been hollowed out by years of corruption and mismanagement.

But in 2014, Russia opted instead for a covert invasion using irregular fighters, mercenaries and unbadged troops. Dudnik’s platoon set up a roadblock about a mile from the border on the morning of May 12 that year. Within hours, they came under assault but, despite being understrength and outnumbered, they held off several dozen attackers, killing one and capturing another.

“They didn’t expect us to fight back," Dudnik said.

The Russian prisoner carried a piece of paper listing the platoon’s location, number and vehicles, indicating local collaborators had given them away, he said. In one car, they found a suitcase stuffed with U.S. dollars—evidence, he said, that the attackers were mercenaries.

Other units in Dudnik’s battalion didn’t fare so well. He recalled seeing armored vehicles sweep past, then limp back later damaged and in smaller numbers. Days after Dudnik’s unit left one location near the border, the place was devastated by artillery fire from Russian territory, killing dozens.

“We were in the palm of their hand there," Dudnik said.

Ukraine was unable to oust the Russian forces from parts of the east, and fighting wound down after a cease-fire was signed. Dudnik trained as a specialist in air-defense systems. Stationed near the prosperous eastern city of Bakhmut in 2016, he rented an apartment with his girlfriend. Bakhmut, he said, became like a second hometown. They later married and had a son.

In 2018, he sought out a new challenge working in a military-recruitment office. By 2021, he was ready for a change and headed to the Czech Republic, where he found mostly manual work before heading home to renew his visa.

Then, in early 2022, Russia launched a full-scale invasion. Dudnik re-enlisted, this time with the 93rd Mechanized Brigade. Ukraine’s military and its population had been steeled by the long conflict with Russia and were more prepared than in 2014.

Now a sergeant, Dudnik saw his first major action in September in Soledar, a salt-mining town that abuts Bakhmut. A missile hit the headquarters he was guarding, causing the roof to collapse and crushing two soldiers nearby. He got out largely unscathed save for cuts and concussion that left him sensitive to loud noises.

“It was like being born a second time," he said.

He began to carry a U.S.-made Stinger, even though he hadn’t trained on that air-defense system and learned how to use it by watching videos on his cellphone. The first time he fired it in October, he missed. “I screwed up," he said.

Russian troops took the town in December, and Dudnik was sent on leave, followed by training and a return to action in Bakhmut in January 2023. The city was nothing like the place he remembered from 2016. He couldn’t make it to the apartment he stayed in then as it was on the eastern side of the city, which was already in Russian hands.

Last March, Dudnik and his unit were at an apartment block targeting Russian warplanes that were launching bombing runs on Ukrainian infantry in the city. A camera crew from national television tagged along. That morning, his commander gave him a fresh batch of Soviet-era Igla-1 rockets even though they were marked as defective. Another soldier gave him a launching mechanism captured from the Russians.

Dudnik stationed himself on the seventh floor. The windows had been blown out by a tank round that had hit days earlier, exposing him to a freezing draft. He drew the curtain to avoid being seen and looked through a tiny peephole cut in the cloth.

“Readiness 1," came a message over the radio. That meant a Russian warplane had been spotted on radar, so Dudnik raised the Igla onto his shoulder. After 15 minutes, his shoulder was going numb, so he put it down on the window ledge.

Then he heard the plane. He yelled at the camera crew to get out of the way. He knew he had a few seconds to make the shot. He couldn’t acquire the target in manual mode, so he switched to automatic and the missile launched. The plane slowed down as it started to turn and tried to pick up speed to evade the missile. The pilot released chaff to try to confuse the missile, but it was too late. The missile slammed into the plane, which burst into flames and began pouring out smoke. The pilot ejected.

Dudnik was congratulated by commanders and feted on television. But there was no video evidence of him firing the missile that downed the plane, so he missed out on the reward of just over $3,000.

Following a whirlwind tour of TV interviews, he returned to fight in Bakhmut until it was lost in May, but didn’t manage to shoot down another plane.

“Russian pilots are aces, not idiots," he said.

After leave, his unit returned to a front-line village near Bakhmut called Klishchiivka. For now, they are holding off Russian assaults despite being severely outnumbered and low on ammunition. Dudnik now spends much of his time targeting small Russian aerial drones that either detonate themselves or drop explosives. One got through recently and dropped a grenade on Dudnik’s team as they were arriving at their position. The shrapnel spattered his rucksack, sparing him injury but leaving him picking metal chunks out of the salami he had been carrying.

Even getting to the front is a challenge these days, requiring a fight through mud often in civilian vehicles that soldiers purchased themselves with help from friends and relatives. After his years of service, Dudnik suffers from heart trouble and a bad back as well as the effects of several concussions.

“There’s a bit of gunpowder left," he said. “But it’s slowly running out."

Ievgeniia Sivorka and Oksana Grytsenko contributed to this article.

Write to James Marson at james.marson@wsj.com