This video is part of Crash Course World History, written by Raoul Meyer and Teva Vidal, and presented by John Green.
After World War II tension grew between the USA and the Soviet Union.
Capitalism depends on expanding markets, and communism requires universal participation to be effective. The two became rivals, each trying to propagate its system. The Cold War period also saw a couple of open wars (in Vietnam and Korea) in which the USA engaged in order to prevent communism from spreading.
Meanwhile, the rivals built up such huge nuclear arsenals that they could have destroyed the world several times over. To curb this dangerous posturing they agreed to a strategy known as ‘MAD’ — mutually assured destruction. As either could destroy the other, both held off and the conflicts were indirect and underhand.
Both sides helped to prop other governments, the USA notably in Latin America. And both were brutally repressive where they saw fit.
Eventually, Soviet President Mikhail Gorbachev introduced a new openness (glasnost) into his society, and the Soviet bloc fell in 1989-90. 89 communist countries held elections and abandoned communism, leaving China and a few others to work out how to combine communist ideology with capitalism.