The Union of Soviet Socialist Republics (USSR), also known as the Soviet Union, was a transcontinental country that existed from 1922 to 1991. It stretched across much of Eurasia and was the world's largest country by area. The USSR bordered twelve countries. It was a diverse multinational state, organized as a federal union of national republics, with the Russian Soviet Federative Socialist Republic being the largest and most populous. Moscow was its capital and largest city.
The Soviet Union was the first country to declare itself socialist and aim to build a communist society. It was known for its centralized government and command economy, with the state controlling the means of production, distribution, and exchange. The USSR emerged as one of the world's two superpowers during the Cold War, engaging in an arms race and proxy wars with the United States. Key features included a one-party state under the Communist Party, rapid industrialization, forced collectivization of agriculture, and advancements in science and space exploration. The Soviet Union dissolved in 1991, leading to the independence of several former Soviet states.