The Soviet Union, officially known as the Union of Soviet Socialist Republics (USSR), was a socialist state that existed from 1922 to 1991. It was a federation of multiple republics, with Russia being the largest and most influential. The government was based on the principles of Marxism-Leninism, and it aimed to create a classless society through state control of the economy and collective ownership of resources. During its existence, the Soviet Union became a major world power, playing a significant role in global events such as World War II and the Cold War. It was known for its space achievements, including launching the first human, Yuri Gagarin, into space in 1961. The USSR dissolved in 1991, leading to the independence of its republics and significant political and economic changes in the region.