Soviet Union, Union of Soviet Socialist Republics (USSR).

The Soviet Union, or Union of Soviet Socialist Republics (USSR), was established under Vladimir Lenin and the Communist Party in 1922, after five violent years of revolution and civil war that overturned the imperial regime.

At its height, the country consisted of 15 republics and encompassed nearly one-sixth of the earth's land mass. The USSR underwent massive changes in the 1930s and 1940s during Joseph Stalin’s brutal transformation of Soviet industry and society, which led to the imprisonment and death of millions.

In the decades after World War II, the USSR and non-communist west, locked in a prolonged “Cold War,” repeatedly clashed over communist aggression and expansion in Eastern Europe, Asia and Latin America. In the 1980s, a new spirit of reform, epitomized by Mikhail Gorbachev's programs of glasnost (openness) and perestroika (restructuring), took hold in both the USSR and communist Eastern Europe.

As former satellite nations broke free of Soviet control, individual republics within the USSR also struggled for independence. Unable to withstand these internal changes, the Soviet Union was formally dissolved in December 1991.

At it's height, the USSR extended more than 6,800 miles from east to west, covering 11 of the world's 24 time zones.