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The Soviet Union,[e] officially the Union of Soviet Socialist Republics[f] (USSR),[g] was a federal socialist state in Northern Eurasia that existed from 1922 to 1991. Nominally a union of multiple national Soviet republics,[h] it was a one-party state (until 1990) governed by the Communist Party, with Moscow as its capital in its largest republic, the Russian SFSR. Other major urban centers were Leningrad (Russian SFSR), Kiev (Ukrainian SSR), Minsk (Byelorussian SSR), Tashkent (Uzbek SSR), Alma-Ata (Kazakh SSR) and Novosibirsk (Russian SFSR). It was the largest country in the world by surface area,[9] spanning over 10,000 kilometers (6,200 mi) east to west across 11 time zones and over 7,200 kilometers (4,500 mi) north to south. Its territory included much of Eastern Europe, parts of Northern Europe and Western Asia, and all of Northern and Central Asia. Its five climate zones were tundra, taiga, steppes, desert, and mountains. Its diverse population was collectively known as Soviet people.

The Soviet Union had its roots in the October Revolution of 1917 when the Bolsheviks, headed by Vladimir Lenin, overthrew the Provisional Government that had earlier replaced the monarchy of the Russian Empire. They established the Russian Soviet Republic,[i] beginning a civil war between the Bolshevik Red Army and many anti-Bolshevik forces across the former Empire, among whom the largest faction was the White Guard, which engaged in violent anti-communist repression against the Bolsheviks and their worker and peasant supporters known as the White Terror. The Red Army expanded and helped local Bolsheviks take power, establishing soviets, repressing their political opponents and rebellious peasants through Red Terror. By 1922, the Bolsheviks had emerged victorious, forming the Soviet Union with the unification of the Russian, Transcaucasian, Ukrainian and Byelorussian republics. The New Economic Policy (NEP), which was introduced by Lenin, led to a partial return of a free market and private property; this resulted in a period of economic recovery.

Following Lenin's death in 1924, Joseph Stalin came to power. Stalin suppressed all political opposition to his rule inside the Communist Party and initiated a centrally planned economy. As a result, the country underwent a period of rapid industrialization and forced collectivization, which led to significant economic growth, but also led to a man-made famine in 1932–1933 and expanded the Gulag labour camp system originally established in 1918. Stalin also fomented political paranoia and conducted the Great Purge to remove his actual and perceived opponents from the Party through mass arrests of military leaders, Communist Party members, and ordinary citizens alike, who were then sent to correctional labor camps or sentenced to death.

In the mid-1980s, the last Soviet leader, Mikhail Gorbachev, sought to further reform and liberalize the economy through his policies of glasnost and perestroika. The goal was to preserve the Communist Party while reversing economic stagnation. The Cold War ended during his tenure and in 1989, Warsaw Pact countries in Eastern Europe overthrew their respective Marxist-Leninist regimes. In particular, the indecisive action of the Eastern European rulers after the Pan-European Picnic caused the fall of the Iron Curtain, which shattered the formerly powerful communist unity. This led to the rise of strong nationalist and separatist movements inside the USSR as well. Central authorities initiated a referendum—boycotted by the Baltic republics, Armenia, Georgia, and Moldova—which resulted in the majority of participating citizens voting in favor of preserving the Union as a renewed federation. In August 1991, a coup d'état was attempted by Communist Party hardliners. It failed, with Russian President Boris Yeltsin playing a high-profile role in facing down the coup, resulting in the banning of the Communist Party. On 25 December 1991, Gorbachev resigned and the remaining twelve constituent republics emerged from the dissolution of the Soviet Union as independent post-Soviet states. The Russian Federation (formerly the Russian SFSR) assumed the Soviet Union's rights and obligations and is recognized as its continued legal personality.

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