Soviet Union

The Union of Soviet Socialist Republics (Russian: Сою́з Сове́тских Социалисти́ческих Респу́блик, Soyuz Sovetskikh Sotsialisticheskikh Respublik) abbreviated to USSR (Russian: СССР, SSSR) or the Soviet Union (Russian: Советский Союз, Sovetsky Soyuz), was a constitutionally socialist state that existed between 1922 and 1991, ruled as a single-party state by the Communist Party with its capital as Moscow. A union of 15 subnational Soviet republics, its government and economy were highly centralised.

The Soviet Union had its roots in the Russian Revolution of 1917, which deposed Nicholas II, ending three hundred years of Romanov dynastic rule. The Bolsheviks, led by Vladimir Lenin, stormed the Winter Palace in Petrograd and overthrew the Provisional Government. The Russian Socialist Federative Soviet Republic was established and a civil war began. The Red Army entered several territories of the former Russian Empire and helped local communists seize power. In 1922, the Bolsheviks 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 late 1920s. Stalin committed the state ideology to Marxism–Leninism and a centralised planned economy was initiated. 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. However, Stalin repressed both Communist Party members and elements of the population through his authoritarian rule.

During World War II, Nazi Germany invaded the Soviet Union in 1941, opening the largest and bloodiest theatre of war in history and violating an earlier non-aggression pact between the two countries. The Soviet Union suffered the largest loss of life in the war, but halted the Axis advance at intense battles such as at Stalingrad, eventually driving through Eastern Europe and capturing Berlin in 1945. Having played the decisive role in the Allied victory in Europe, the Soviet Union consequently occupied much of Central and Eastern Europe and emerged as one of the world's two superpowers after the war. Together with these new socialist satellite states, through which it established economic and military pacts, it became involved in the Cold War, a prolonged ideological and political struggle against the Western Bloc, and in particular the other superpower, the United States.

A de-Stalinisation period followed Stalin's death, reducing the harshest aspects of society. The Soviet Union then went on to initiate significant technological achievements of the 20th century, including launching the first ever satellite and world's first human spaceflight, which led it into the Space Race. The Cuban Missile Crisis in 1962 marked a period of extreme tension between the two superpowers, considered the closest to a mutual nuclear confrontation. In the 1970s, a relaxation of relations followed, but tensions resumed when, after a Communist-led revolution in Afghanistan, Soviet forces entered the country by request of the new regime. The occupation drained economic resources and dragged on without achieving meaningful political results.

In the late 1980s the last Soviet leader, Mikhail Gorbachev, sought reforms in the Union, introducing the policies of glasnost and perestroika in an attempt to end the period of economic stagnation and democratize the government. However, this led to the rise of strong nationalist and separatist movements. By 1991, the country was in turmoil as the Baltic republics began to secede. A referendum resulted in the vast majority of participating citizens voting in favour of preserving the Union as a renewed federation. In August 1991, a coup d'état attempt by hardliners against Gorbachev and aimed at preserving the country, instead led to its collapse. On 25 December 1991, the USSR was dissolved into 15 post-Soviet states. The Russian Federation, successor of the Russian SFSR, assumed the Soviet Union's rights and obligations and is recognised as its continued legal personality.