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).
Ukraine after the Russian Revolution
Various factions fought over Ukrainian territory after the collapse of the Russian Empire following the Russian Revolution of 1917 and after the First World War ended in 1918, resulting in the collapse of Austria-Hungary, which had ruled Ukrainian Galicia. The crumbling of the empires had a great effect on the Ukrainian nationalist movement, and in a short period of four years a number of Ukrainian governments sprang up. This period was characterized by optimism and by nation-building, as well as by chaos and civil war. Matters stabilized somewhat in 1921 with the territory of modern-day Ukraine divided between Soviet Ukraine (which would become a constituent republic of the Soviet Union in 1922) and Poland, and with small ethnic-Ukrainian regions belonging to Czechoslovakia and to Romania.