Soviet Union

The Union of Soviet Socialist Republics^[t] (USSR),^[u] commonly known as the Soviet Union,^[v] was a transcontinental country that spanned much of Eurasia from 1922 until it dissolved in 1991. During its existence, it was the largest country by area, extending across eleven time zones and sharing borders with twelve countries, and the third-most populous country.^[w] An overall successor to the Russian Empire, it was nominally organized as a federal union of national republics, the largest and most populous of which was the Russian SFSR.^[x] In practice, its government and economy were highly centralized. As a one-party state governed by the Communist Party of the Soviet Union (CPSU), it was the flagship communist state. Its capital and largest city was Moscow.

The Soviet Union's roots lay in the October Revolution of 1917. The new government, led by Vladimir Lenin, established the Russian SFSR, the world's first constitutionally communist state. The revolution was not accepted by all within the Russian Republic, resulting in the Russian Civil War. The Russian SFSR and its subordinate republics were merged into the Soviet Union in 1922. Following Lenin's death in 1924, Joseph Stalin came to power, inaugurating rapid industrialization and forced collectivization that led to significant economic growth but contributed to a famine between 1930 and 1933 that killed millions. The Soviet forced labour camp system of the Gulag was expanded. During the late 1930s, Stalin's government conducted the Great Purge to remove opponents, resulting in large scale deportations, arrests, and show trials accompanied by public fear. Having failed to build an anti-Nazi coalition in Europe, the Soviet Union signed a non-aggression pact with Nazi Germany in 1939. Despite this, in 1941 Germany invaded the Soviet Union in the largest land invasion in history, opening the Eastern Front of World War II. The Soviets played a decisive role in defeating the Axis powers while liberating much of Central and Eastern Europe. However they would suffer an estimated 27 million casualties, which accounted for most losses among the victorious Allies. In the aftermath of the war, the Soviet Union consolidated the territory occupied by the Red Army, forming satellite states, and undertook rapid economic development which cemented its status as a superpower.

Geopolitical tensions with the United States led to the Cold War. The American-led Western Bloc coalesced into NATO in 1949, prompting the Soviet Union to form its own military alliance, the Warsaw Pact, in 1955. Neither side engaged in direct military confrontation, and instead fought on an ideological basis and through proxy wars. In 1953, following Stalin's death, the Soviet Union undertook a campaign of de-Stalinization under Nikita Khrushchev, which saw reversals and rejections of Stalinist policies. This campaign caused ideological tensions with the PRC led by Mao Zedong, culminating in the acrimonious Sino-Soviet split. During the 1950s, the Soviet Union expanded its efforts in space exploration and took a lead in the Space Race with the first artificial satellite, the first human spaceflight, the first space station, and the first probe to land on another planet. In 1985, the last Soviet leader, Mikhail Gorbachev, sought to reform the country through his policies of glasnost and perestroika. In 1989, various countries of the Warsaw Pact overthrew their Soviet-backed regimes, leading to the fall of the Eastern Bloc. A major wave of nationalist and separatist movements erupted across the Soviet Union, primarily in Azerbaijan, Georgia and the Baltic states. In 1991, amid efforts to preserve the country as a renewed federation, an attempted coup against Gorbachev by hardline communists prompted the largest republics—Ukraine, Russia, and Belarus—to secede. On 26 December, Gorbachev officially recognized the dissolution of the Soviet Union. Boris Yeltsin, the leader of the Russian SFSR, oversaw its reconstitution into the Russian Federation, which became the Soviet Union's successor state; all other republics emerged as fully independent post-Soviet states. The Commonwealth of Independent States was formed in the aftermath of the disastrous Soviet collapse, although the Baltics would never join.

During its existence, the Soviet Union produced many significant social and technological achievements and innovations. The USSR was one of the most advanced industrial states during its existence. It had the world's second-largest economy and largest standing military. An NPT-designated state, it wielded the largest arsenal of nuclear weapons in the world. As an Allied nation, it was a founding member of the United Nations as well as one of the five permanent members of the United Nations Security Council. Before its dissolution, the Soviet Union was one of the world's two superpowers through its hegemony in Eastern Europe and Asia, global diplomacy, ideological influence (particularly in the Global South), military might, economic strengths, and scientific accomplishments.

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