Dolyna, Ukraine
CNN
 — 

A soldier in a Ukrainian uniform morosely contemplates the ruins of an Orthodox monastery in Ukraine’s eastern Donetsk region.

“This is a result of Putin’s war,” he says, angrily, as he paces through the wreck. “As a Christian, this is very offensive to me.”

The soldier, whose name CNN agreed not to reveal to protect his identity, goes by the call-sign “Caesar.” He is one of hundreds, if not thousands, fighting to keep the town of Bakhmut, the current epicenter of the war, in Ukrainian hands.

But there’s one thing that sets him apart from most of those who share the same goal: he’s Russian.

“From the first day of the war, my heart, the heart of a real Russian man, a real Christian, told me that I had to be here to defend the people of Ukraine,” Caesar explains. “We are now fighting in the Bakhmut direction, this is the hottest part of the front.”

Few, if any, buildings of the eastern Ukrainian town have been spared by the unending artillery barrages fired from side to side. Many of the structures have been completely destroyed, others left uninhabitable with collapsed sections, in apocalyptic scenes reminiscent of the battered city of Mariupol, captured by Russia earlier in the war.

“After the (Russian) mobilization (in September), Putin threw all his forces (at Bakhmut) in order to achieve a breaking point in the war, but we are putting up a fierce defensive fight,” Caesar says.

Much of Ukraine’s resisting force has had to hunker down in muddy trenches, fighting tooth and nail to deny Russian forces a victory they desperately crave.

“The fighting is very brutal now,” Caesar explains.

A few miles away from the battle, but still in earshot of the constant thuds and explosions, Caesar’s commitment is unflinching and he does not regret his decision to join Ukraine’s foreign legion.

While the urge to sign up came early on in the conflict, he could only leave his home country, with his close family, and join the Ukrainian military in the summer.

“It was a very difficult process,” he says. “It took me several months to finally join the ranks of the defenders of Ukraine.”

Now with his family in Ukraine – where he considers them to be safer – Caesar says he is one of around 200 Russian citizens currently fighting alongside Ukrainian forces, against their own country’s armies. CNN has not been able independently to confirm this number.

In Caesar’s view, Moscow’s forces are not true Russians.

“Yes, I kill my countrymen, but they have become criminals,” he explains. “They came to a foreign land to rob and kill and destroy. They kill civilians, children and women.”

“I have to confront this,” he added.

Caesar is a self-confessed opponent of what he says is a “tyrannical regime” headed by Russian President Vladimir Putin, not just in Ukraine but also inside his own country. And in his confrontation of the war, he has had to shoot at least 15 Russian soldiers on the battlefield, he claims.

They are lives he did not pity and killings he does not regret, he says.

“I am fighting a noble fight and I am doing my military and Christian duty; I am defending the Ukrainian people,” Caesar says. “And when Ukraine is free, I will carry my sword to Russia to free it from tyranny.”

Caesar’s ideological drive is not the only reason some Russians have chosen to side with Ukrainians on the battlefield. For many the motivation lies closer to the heart.

“Silent,” the call-sign of another Russian soldier whose full name CNN is not disclosing for his safety, was visiting Ukraine when Russian missiles and artillery shells started landing in its towns and cities on February 24.

“I came to Ukraine at the beginning of February to visit my relatives. I stayed here and war started,” Silent says.

He says he joined the Ukrainian military shortly after he saw the atrocities perpetrated by Russian soldiers in the suburbs of Bucha, Irpin and Borodianka, just outside the Ukrainian capital, Kyiv. Evidence of mass graves and civilian executions in those areas emerged following the withdrawal of Russian forces from the Kyiv region in early April.

Russia has previously denied allegations of war crimes and claimed its forces do not target civilians, despite extensive evidence gathered by international human rights experts, criminal investigators and international media in multiple locations.

“I was just outside Kyiv, not far from those places, and when they were kicked out of that territory, we went there to help people and saw what they had done,” Silent says. “Dead bodies, children, women, executions … When you see it in person … of course everything inside turned upside down.”

He adds: “I decided to stay here until the end and join the legion.”

Silent says his best friend has recently been forcibly mobilized into Russia’s army back home. Silent says they’ve discussed the terrifying fact that it’s conceivable they could end up on opposite sides on a Ukrainian battlefield.

“It’s weird that that could happen – especially as he wants to leave Russia and wants to come to fight with me against Putin’s army in Ukraine. We’re trying to get him out but he’s being held by the Russian army,” says Silent.

His family, like many in Russia and Ukraine, has roots in both countries. His wife and two children are now living with him in Ukraine but other relatives remain in Russia. Silent says that although they have stayed behind, they see through Putin’s propaganda on the war, still described as a “special military operation” by the Kremlin.

“They understand what is going on: Russia invaded Ukraine,” he says, adding that his relatives were not angry with him. “They know my character, that if I have made a decision, I will act until the end.

“They told me to stay safe.”

Another soldier, who goes by the call-sign “Vinnie,” insists on covering his face with a balaclava, fearing that the Kremlin’s long arm might try to reach him in Ukraine.

“My family is not here with me right now,” he explains. He says he is fighting for them and for their future, but still fears what Moscow’s security apparatus might do to them.

“My children, my wife, who I love very much, they’re my everything, my whole life,” he says, with a sparkle in his eyes and a smile that can be detected through the cloth covering his face.

“If I show my face … I worry about them, because there’ll be no one to protect them,” he adds.

It’s one of the added risks for Russian citizens risking their lives for Ukraine, but not the only one. Russian soldiers fighting for Ukraine could face tougher consequences than their Ukrainian counterparts if they’re captured by the enemy.

Last month, a soldier who deserted the Russian mercenary group Wagner and crossed onto the Ukrainian side, Yevgeny Nuzhin, was brutally murdered with a sledgehammer after he went back to Russia.

His execution was applauded by the head of the group, Russian oligarch Yevgeny Prigozhin. Without directly acknowledging that Wagner fighters had carried out the murder, Prigozhin said: “Nuzhin betrayed his people, betrayed his comrades, betrayed them consciously. He was not taken prisoner, nor did he surrender. Rather, he planned his escape. Nuzhin is a traitor.”

This kind of example is why Vinnie is certain of what will await him should he be captured.

“There won’t be an exchange for sure. It will be the end, 100%,” he says. “It will just be more painful.”

But pain and death are not a part of this unit’s lexicon, even as they face overwhelming odds in Bakhmut.

Russia has been trying to capture the town for months and has thrown large numbers of men at Ukrainian defenses in an attempt to break them. But they haven’t broken Vinnie.

“I am defending the country, I am defending homes, women, children, people who cannot defend themselves,” he says. “My conscience is absolutely clear.”

Caesar, standing amid the remains of the Orthodox monastery, is equally defiant, saying not even the prospect of defeat will make him waver.

“I will stay here while my heart will beats. I will fight to defend Ukraine,” he says.

“And when we have defended Ukraine I will liberate my country.”