The
Soviet Union,[d] officially the Union of Soviet Socialist Republics[e] (USSR[f]), was
a socialist state that spanned Europe and Asia during its existence from 1922 to 1991. It was
nominally a federal union of multiple national republics;[g] in practice its
government and economy were highly centralized until its final years. The country was a one-
party state prior to 1990 governed by the Communist Party of the Soviet Union, with Moscow as
its capital within its largest and most populous 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, covering over 22,402,200 square kilometres (8,649,500 sq mi),
and spanning eleven time zones.
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,
the world's first constitutionally guaranteed socialist state.[h] Tensions escalated into 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. The White Guard engaged in violent anti-
communist repression against the Bolsheviks and suspected worker and peasant Bolsheviks
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 balance of power had shifted and the Bolsheviks had emerged victorious,
forming the Soviet Union with the unification of the
Russian, Transcaucasian, Ukrainian and Byelorussian republics. Upon the conclusion of the civil
war Lenin's government introduced The New Economic Policy (NEP), which 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 inaugurated a command 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. 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.
On 23 August 1939, after unsuccessful efforts to form an anti-fascist alliance with Western
powers, the Soviets signed the non-aggression agreement with Nazi Germany. After the start of
World War II, the formally neutral Soviets invaded and annexed territories of several Eastern
European states, including eastern Poland and the Baltic states. In June 1941 the Germans
invaded, opening the largest and bloodiest theater of war in history. Soviet war
casualties accounted for the majority of Allied casualties of the conflict in the process of acquiring
the upper hand over Axis forces at intense battles such as Stalingrad. Soviet forces
eventually captured Berlin and won World War II in Europe on 9 May 1945. The territory
overtaken by the Red Army became satellite states of the Eastern Bloc. The Cold War emerged
in 1947, where the Eastern Bloc confronted the Western Bloc, which would unite in the North
Atlantic Treaty Organization in 1949.
Following Stalin's death in 1953, a period known as de-Stalinization and the Khrushchev
Thaw occurred under the leadership of Nikita Khrushchev. The country developed rapidly, as
millions of peasants were moved into industrialized cities. The USSR took an early lead in
the Space Race with the first ever satellite and the first human spaceflight and the first probe to
land on another planet, Venus. In the 1970s, there was a brief détente of relations with the
United States, but tensions resumed when the Soviet Union deployed troops in Afghanistan in
1979. The war drained economic resources and was matched by an escalation of American
military aid to Mujahideen fighters.
