Ukrainian Soviet Socialist Republic
Eventually, after the creation of the Communist Party (Bolshevik) of Ukraine in Moscow, a third Ukrainian Soviet government was formed on 21 December 1919 that initiated new hostilities against Ukrainian nationalists as they lost their military support from the defeated Central Powers. Eventually, the Red Army ended up controlling much of the Ukrainian territory after the Polish-Soviet Peace of Riga. On 30 December 1922, along with the Russian, Byelorussian, and Transcaucasian republics, the Ukrainian SSR was one of the founding members of the Union of Soviet Socialist Republics (USSR).
History of Ukraine
The Second World War began in September 1939, when Hitler and Stalin invaded Poland, the Soviet Union taking most of Western Ukraine. Nazi Germany with its allies invaded the Soviet Union in 1941. Some Ukrainians initially regarded the Wehrmacht soldiers as liberators from Soviet rule, while others formed a partisan movement. Some elements of the Ukrainian nationalist underground formed a Ukrainian Insurgent Army that fought both Soviet forces and the Nazi. Others collaborated with the Germans. In Volhynia, Ukrainian fighters committed a massacre against up to 100,000 Polish civilians. Residual small groups of the UPA-partizans acted near the Polish and Soviet border as long as to the 1950s.