What was the containment policy during the late 1940s through the early 1970s?
The policy of containment was the main policy that the United States pursued for most of the Cold War. The basic idea of this policy was that communism should not be allowed to spread beyond the countries that were already communist. This policy did not envision trying to overthrow communist governments that already existed. Instead, it simply aimed to prevent any further countries from becoming communist.
At the end of World War II, the Soviet Union was given control of Eastern Europe. The Soviets quickly moved to exert very tight control over these countries. This made people in the United States very worried that the Soviets were going to try to spread communism to as much of the world as they possibly could. In response to this fear, they developed the policy of containment. The US would not try to overthrow any communist governments, but it would do things like the Truman Doctrine and the Marshall Plan (and later the Vietnam War) to prevent communism from spreading.