Many Russians sent to Ukraine due to the willingness of Ukrainians to fight against USSR in WWII.
The Wagner Russian mercenaries with Spetznatz background were fairly ineffective in Ukraine, as Ukraine government still exists.
Part of the payback was the ill advised Wagner Russian attack against US special ops in Syria which resulted in over 200 Russians being killed.
Lol..since removing the regime in Kiev was never a stated goal of the Donbas separatists, the fact the Kiev regime still stands is meaningless.
Ask the Ukie survivors of the Debaltsolvo pocket how effective the DPR fighters are tho...