At a simple shooting range outside Kyiv, a group of 20 Russian citizens clad in Ukrainian uniforms practiced firing assault rifles and machine guns.

Soon, they expect to be taking aim at the Russian army.

Their commander, a Ukrainian who introduced himself by the callsign Batya, said some of the recruits to Ukraine’s newly-formed Siberian Battalion, the yellow and blue flag on their sleeves, were now ready for battle.

A Ukrainian military officer, who asked to remain anonymous, said most of the unit’s 50 members came from Russia, travelling through third countries to reach Ukraine.

The officer said most are from among the indigenous peoples of Siberia and recruits said they want to fight against what they said was Russian imperialism both inside Ukraine and in their homelands.

“Starting from Tsarist Russia, when they colonized us, they destroyed our culture, our language and traditions. It was Russification, pure and simple,” Gennadiy, a 29-year-old with the callsign Buryat, which refers to his homeland of Buryatia on the shores of Lake Baikal in Siberia, told Reuters.

Military analysts say that Buryatia, as well as some of the other Russian regions which are home to indigenous peoples, have provided a disproportionately large number of soldiers for Russia’s war effort.

Gennadiy said many people were forcibly mobilised by Russia, while others were tempted by salaries that could be more than ten times the wages earned by some people in the region.

Civil society group Free Buryatia Foundation has said the drive to mobilise a disproportionate number of Buryats was a political choice, as the Kremlin saw Buryatia as posing less of a risk in terms of anti-government protests.