BBC finds Russians fighting in eastern Ukraine9 January 2015 Last updated at 06:34 GMT
It is eight months since the start of the conflict in eastern Ukraine, and the fighting has claimed more than 4,000 lives.
Russia has consistently denied its forces are involved, but the BBC has spoken to Russian fighters in Ukraine who talk openly about taking on the Ukrainian army.
http://www.bbc.com/news/world-europe-30739110