After World War II, the United States and the Soviet Union emerged as superpowers with vastly different ideologies and competing interests. This led to a period of intense hostility and distrust between the two nations, known as the Cold War. The tensions between the US and the USSR were largely driven by their opposing political and economic systems, with the US promoting capitalism and democracy and the USSR promoting communism. The Cold War lasted for several decades and saw numerous proxy wars and other conflicts, as well as a constant arms race and the development of nuclear weapons. Ultimately, the Cold War ended with the collapse of the Soviet Union in 1991.