The Cold War was a period of time in which there was great political and military tension between the United States and the Soviet Union. Both sides anticipated using mass nuclear weapons, however there were no major fights between them, which gave the Cold War its name. It started after WWII when the Soviet Union started spreading Communism in many European countries. The United States started a strategic global containment (the containment of Communism, keeping it from spreading to other countries) to keep the Soviet Union from spreading. The Soviet Union spread Communism to a part of Europe called the Eastern Bloc, and, in turn, the United States sent aid to the Western Bloc of Europe to stop Communism from spreading to those countries. This created tension between the U.S. and the USSR, called the Cold War.