The following outline is provided as an overview of and topical guide to the Soviet Union: Soviet Union – was a socialist state on the Eurasian continent that existed from 1922 to 1991. A union of multiple subnational Soviet republics, its government and economy were highly centralized. The Soviet Union was a one-party state, governed by the Communist Party with Moscow as its capital. It was a major ally during World War II, a main participant in the Cold War, and it grew in power to become one of the world's two superpowers (the other being the United States). The Soviet Union collapsed in 1991.