The Russian Revolution of 1917 caused the downfall of the Russian Empire. Following the Russian Revolution, there was a struggle for power between the Bolshevik party, led by Vladimir Lenin, and the anti-communist White movement. In December 1922, the Bolsheviks won the civil war, and the Soviet Union was formed with the merger of the Russian Soviet Federative Socialist Republic, the Transcaucasian Socialist Federative Soviet Republic, the Ukrainian Soviet Socialist Republic and the Byelorussian Soviet Socialist Republic.
Following the death of Vladimir Lenin in 1924, Joseph Stalin took power, leading the USSR through a large-scale industrialization program. Stalin established a planned economy and suppressed political opposition to him and the Communist party.
In June 1941, Nazi Germany and its allies invaded the Soviet Union, breaking the non-aggression pact, which the latter had signed in 1939. After four years of brutal warfare, the Soviet Union emerged victorious as one of the world's two superpowers, the other being the United States.
The Soviet Union and its Eastern European satellite states engaged in the Cold War, a prolonged global ideological and political struggle against the United States and its Western Bloc allies, which it ultimately abandoned in the face of economic troubles and both domestic and foreign political unrest. In the late 1980s, the last Soviet leader Mikhail Gorbachev tried to reform the state with his policies of perestroika and glasnost, but the Soviet Union collapsed and was formally dissolved in December 1991 after the abortive August coup attempt. The Russian Federation assumed its rights and obligations.