Why did westen nations want to contain or stop the spread of communism?

The domino theory, which governed much of U.S. foreign policy beginning in the early 1950s, held that a communist victory in one nation would quickly lead to a chain reaction of communist takeovers in neighboring states. In Southeast Asia, the United States government used the domino theory to justify its support of a non-communist regime in South Vietnam against the communist government of North Vietnam, and ultimately its increasing involvement in the long-running Vietnam War (1954-75). In fact, the American failure to prevent a communist victory in Vietnam had much less of a global impact than had been assumed by the domino theory. Though communist regimes did arise in Laos and Cambodia after 1975, communism failed to spread throughout the rest of Southeast AsiaAll done enjoy

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Primary sources are usually  more accurate and are written by someone who experienced it or witnessed it. secondary sources are those who heard of it after the fact that can lose details and or twist the event in a light that benefits them.