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).
Ukrainian Soviet Socialist Republic
In September 1939, the Soviet Union invaded Poland and occupied Galician lands inhabited by Ukrainians, Poles and Jews adding it to the territory of the Ukrainian SSR. In 1945, these lands were permanently annexed, and the Transcarpathia region was added as well, by treaty with the post-war administration of Czechoslovakia. Following eastward Soviet retreat in 1941, Ufa became the wartime seat of the Soviet Ukrainian government.