A Russian expat claims that around 42,000 different Russian troops have participated in the fighting in Ukraine at some time.

He also claims that many of them are conscripts and that special troops are deployed behind them to shoot them if they run away. The "Dzerzhinskiy division" is apparently named after the man who lead the Soviet political repression police agency.

I don't know how much confidence to place in the author of this report and I won't treat this as certain truth.