The Cold War was a period of geopolitical tension between the United States and Soviet Union from 1947 to 1991. It started with the breakdown of the alliance between the US, Britain, and USSR after WWII and emergence of two competing ideologies - democracy and capitalism vs communism. This led to the division of Europe and world into two opposing camps aligned with either the NATO or Soviet blocs. Several proxy wars were fought between the two superpowers during this time until the eventual collapse of the Soviet Union in 1991 ended the Cold War.