Igor Strelkov
Colonel Igor Strelkov (Girkin) is a Russian officer best known for organizing armed resistance in the irredentist Donetsk People's Republic after the Maidan coup in 2014.
Resentment against the new and illegal government existed in other parts of Ukraine as well (incl. Kharkov and Odessa), but only Donetsk and Lugansk attempted to secede from Ukraine.
Strelkov later claimed that he played the key role in this, and that without him and his fellow soldiers there wouldn't be Donetsk and Lugansk People's republics.