The Union of Soviet Socialist Republics abbreviated to USSR (Russian: СССР, tr. SSSR) or the Soviet Union, was a socialist state on the Eurasian continent that existed between 1922 and 1991, governed as a single-party state by the Communist Party with Moscow as its capital. A union of multiple subnational Soviet republics, its government and economy were highly centralized.
The Soviet Union had its roots in the Russian Revolution of 1917, which deposed the imperial autocracy. The majority faction of the Social Democratic Labour Party, led by Vladimir Lenin, then led a second revolution which overthrew the provisional government and established the Russian Socialist Federative Soviet Republic (renamed Russian Soviet Federative Socialist Republic in 1936), beginning a civil war between pro-revolution Reds and counter-revolution Whites. The Red Army entered several territories of the former Russian Empire and organized workers and peasants into soviets under Communist leadership. In 1922, the Communists were victorious, forming the Soviet Union with the unification of the Russian, Transcaucasian, Ukrainian, and Byelorussian republics. Following Lenin's death in 1924, a troika collective leadership and a brief power struggle, Joseph Stalin came to power in the mid-1920s. Stalin committed the state ideology to Marxism–Leninism and initiated a centrally planned economy. As a result, the country underwent a period of rapid industrialisation and collectivisation which laid the basis for its later war effort and dominance after World War II.