Soviet Union

The Union of Soviet Socialist Republics (USSR), also known as the Soviet Union, was a transcontinental country that spanned much of Eurasia from 1922 until its dissolution in 1991. It was the world's third-most populous country, largest by area, and bordered twelve countries. A diverse multinational state, it was organized as a federal union of national republics, the largest and most populous being the Russian Soviet Federative Socialist Republic. In practice, its government and economy were highly centralized. As a one-party state governed by its Communist Party, 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. Following the Bolshevik victory 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 growth but contributed to a 1930s famine killing millions. Soviet forced labour expanded via the Gulag system. Stalin's government conducted the late 1930s Great Purge via deportations, executions, and show trials. Failing to build an anti-Nazi coalition in Europe, the Soviet Union signed a 1939 non-aggression pact with Nazi Germany. Nonetheless, in 1941 Germany invaded the Soviet Union in the largest land invasion in history, opening the Eastern Front of World War II. The Red Army played a decisive role in the Allies defeating the Axis powers, while liberating much of Central and Eastern Europe. At around 27 million casualties, the country suffered the most deaths in World War II. In the war's aftermath, the Soviet Union consolidated territories it occupied into satellite states, and undertook rapid economic development, cementing its status as a superpower.

Geopolitical tensions with the United States led to the Cold War. The US-led Western Bloc coalesced into the NATO military alliance in 1949, prompting the Eastern Bloc to form the Warsaw Pact in 1955. With scant direct combat, the blocs fought via ideological and proxy wars. In 1953, following Stalin's death, Nikita Khrushchev led a campaign of de-Stalinization. Resulting ideological tensions with communist China, led by Mao Zedong, culminated in an acrimonious split. In the following fifteen years the Soviet military suppressed uprisings in East Germany, Hungary and Czechoslovakia, while resolution of the Cuban Missile Crisis narrowly averted a global conflict. Under the 18-year rule of Leonid Brezhnev, prosperity turned toward stagnation and corruption, while US relations eased. In 1985, Mikhail Gorbachev sought reform through his policies glasnost and perestroika. The 1986 Chernobyl disaster, the worst nuclear power disaster in history, contributed to Soviet socio-economic crises. In 1989, most Warsaw Pact countries overthrew their Soviet-backed regimes, ending the Eastern Bloc. Nationalist movements across the Soviet republics declared sovereignty. In 1991, after a successful referendum to establish a renewed federation, a failed coup by hardliners prompted Russia, Ukraine, and Belarus to secede. On 26 December, Gorbachev officially recognized the dissolution of the Soviet Union. Boris Yeltsin, leader of the Russian SFSR, oversaw its reconstitution into the Russian Federation, the Soviet Union's successor state; the fourteen other republics emerged as fully independent states. All except the Baltics joined the Commonwealth of Independent States. The post-Soviet states experienced a humanitarian disaster, and dozens of wars and conflicts.

The Soviet Union was one of the world's two superpowers, with the largest standing military, the second-largest economy, a hegemony in Eastern Europe and Asia, global diplomacy, ideological influence (particularly in the Global South), and scientific and technological accomplishments. It wielded the world's largest arsenals of nuclear, chemical, and biological weapons. Its space program made extensive achievements in the Space Race, including the first artificial satellite and first human spaceflight. Soviet culture was influenced by the official socialist realism style, and later underground samizdat publications. As a major Allied nation, it became one of the five permanent members of the United Nations Security Council. In some post-Soviet states including Russia, nostalgia remains high for the Soviet Union, while others view it negatively. Academics have variously criticized the Soviet system as authoritarian, bureaucratic, and state capitalist, while some have praised its industrialization, scientific capacity, and anti-imperialist influence globally.