The Cold War was a period of geopolitical tension between the United States and the Soviet Union and their respective allies that lasted from the end of World War II in 1945 until the dissolution of the Soviet Union in 1991. While the two superpowers never engaged in direct large-scale military conflict, they competed intensely through proxy wars, an arms race, the Space Race, propaganda, and diplomatic brinkmanship. The era shaped the political geography of the entire 20th century.