The Soviet Union was a Marxist-Leninist state that existed from 1922 to 1991. It was a one-party state governed by the Communist Party of the Soviet Union, with Moscow as its capital. The Soviet Union was a union of 15 Soviet socialist republics and one autonomous republic, with Russia being the largest and most populous republic. The Soviet Union was the first country to declare itself socialist and build towards a communist society. It was also the world's first constitutionally socialist state. The Soviet Union was a superpower that played a major role in the Second World War and the Cold War. It was dissolved in 1991, with Russia becoming its successor state.