Explanation: The Cold War was a period of tension between the Soviet Union and the United States that lasted from the end of World War II until the collapse of the Soviet Union in 1991. The Cold War began when the Soviet Union installed a communist government in Czechoslovakia in 1948. The United States responded by creating the Truman Doctrine, which provided military and economic aid to countries that were resisting communism. The Cold War lasted for over 40 years and led to the development of nuclear weapons and the space race.