The Cold War was a period of tension and hostility between the United States and the Soviet Union from 1945 to 1991. This stemmed from their opposing ideologies of democracy and communism. There were several proxy wars and crises that brought the two superpowers close to direct military conflict, such as the Berlin Airlift, Cuban Missile Crisis, and arms race. Each side formed military alliances like NATO and the Warsaw Pact and engaged in a space race demonstrating their technological prowess. The collapse of the Soviet Union in 1991 marked the end of the Cold War.