KYIV, DECEMBER 14

When Russia's invasion of Ukraine ignited into war, back in Moscow, a young Russian who now goes by the name of Karabas was plunged into despair. Shocked by images of what was happening to Ukrainians in Russian-occupied areas, he decided to act - against Russia, his home and country.

Karabas said he knew that what he was doing was drastic. He packed his bags and decided to find a way to get to Ukraine to join the ranks of Kyiv's troops fighting Russian forces.

It took him almost a year to make it happen.

Today, he is part of the Siberian Battalion, a unit made up of Russians who have joined Ukrainian military ranks to fight against their homeland, hoping someday to help oust Russian President Vladimir Putin. Its members hail mostly from ethnic minorities from Russia's far east.

'I was disillusioned with my own people,' recounted Karabas, who like other fighters in the battalion spoke to The Associated Press on condition that only his military call sign be used.

'That is why I wanted to come here ... and fight for a free Ukraine,' he added.

When Russia launched its full-scale invasion of Ukraine on Feb. 24, 2022, Karabas said he was dismayed by how most Russians he knew either blindly supported Putin or were indifferent to the war.

Sometimes, Karabas said his grief felt so overwhelming, he would break down and cry.

Unlike other volunteer units in Ukraine that have Russian nationals - such as the Freedom of Russia Legion and the Russian Volunteer Corps - the Siberian Battalion is officially part of the regular Ukrainian army.

Its fighters undergo lengthy security checks, which sometimes take up to a year, before they are trained and deployed to the front lines in eastern Ukraine, which has seen some of the most ferocious fighting of the war and where Ukrainian and Russian forces are locked in a grinding battle for control.

Karabas went to Armenia first. There, he sought out Ukrainian friends and learned the language, which he now speaks fluently, refusing to utter a word in his native Russian.

On Wednesday, at a training exercise outside Ukraine's capital of Kyiv, over a dozen Russians from the battalion fired their machine guns during a firing practice, sprinkling cartridges all over the snow blanketing the ground.

Fighters in the battalion from eastern Siberia hope a Ukrainian victory will bring them one step closer to dismantling Moscow's political control over their region, among the poorest in Russia. Those from the area's Yakut and Buryat ethnic communities complain of racism and oppression in Russia, which has driven some activist calls for independence.

Another Russian fighter, who goes by the call sign Holod, openly says he wants Putin's administration removed from power.

'When this happens, we can talk about victory,' he said. 'Russia will at least cease to be a source of sudden aggression.'

Russians like Karabas left their entire lives, including families and friends, behind. They first had to escape to a third country before they could travel on to Ukraine but they say they had no other choice.

Integration into the Ukrainian forces was a lengthy process, they said - their documents were scrutinized, and if they passed this step, they were questioned at length upon arrival in Ukraine.

The battalion, which numbers a few dozen, was created six months ago. Ukrainian military leaders are hopeful more will come to join its ranks and based on applications that have come in so far, they are aiming to have a 300-man-strong battalion of Russian fighters.

Some from the battalion have already been deployed near Avdiivka, a Ukraine-controlled city in the Donetsk region, which Putin's forces have long tried to overrun.

Karabas says 'there must be tens, hundreds of thousands of' other Russians like him, willing to fight with Ukraine.

'I think we should have a lot more (Russian fighters),' he said.