The Soviet Russians decimated Ukraine 1932-33 with the Homolodor. The Nazis retreated with scorched earth policy at end of WWII. Once again Russia is laying waste to people who just want to be left alone.
Ukraine’s border, including Crimea and Donbas, was affirmed by Soviet Russia (under Khrushchev, if I’m correct) in the 1950’s. It was reaffirmed ,including Crimea, by Russia when Ukraine gave up its nukes after dissolution of USSR.
Putin can pound sand.