In December of 1991, representatives from 11 of the USSR's republics announced that they wanted to break away from the Soviet Union and become independent. They did, and the leader of the USSR, Mikhail Gorbachev, resigned from his job on December 25 of 1991.
This event marks the definite end of the Cold War between the US and the USSR. Although the Capitalist and Communist governments will always disagree with one another, at least they won't have to be worried about a nuclear war in the horizon. For now.