What Is "The Domino Effect"?
The domino effect is the idea that some change, small in itself, will cause a similar change nearby, which then will cause another similar change, and so on in linear sequence, by analogy to a falling row of dominoes standing on end.
A well-known use of this metaphor was a justification for the Vietnam War, coined by Eisenhower: if Vietnam fell to communism, then Cambodia would be next, then Laos, and eventually all of Southeast Asia.
This is also known as the domino theory - the idea that if one key nation in a region came under the control of communists, others would follow like toppling dominoes. The theory was used by many United States leaders during the Cold War to justify U.S. intervention in the Vietnam War. The "domino theory" was applied by President Dwight D. Eisenhower and his top advisers in 1954 to describe the prospects of 'communist expansion' in Asia if Indochina were to fall.
The "Domino Theory" was first espoused by name by President Eisenhower in an April 7, 1954 news conference, and was originally applied to Indochina, which includes Vietnam. If Communists succeeded in Indochina, Eisenhower argued, they would then successively take over Burma, Thailand, and Indonesia. This would give them a geographically strategic advantage, from which they would be able to win in Japan, Formosa, the Philippines, Australia, and New Zealand.
The "domino theory" was expounded periodically since 1954 by top U.S. leaders who used it as a justification for expanding military programs throughout the world. The Johnson administration intervened in the latter half of the 1960s with over one-half million troops to keep that "domino" from falling.
Supporters of the "domino theory" argued that a communist victory would mean that U.S. alliance guarantees for other small nations would no longer be credible, and a series of communist victories could be expected. Critics of the theory charged that the Indochinese wars were largely indigenous in nature, that no such monolithic force as "world communism" existed, and that the theory was used as a propaganda scare tactic to try to justify unwarranted intervention policies. In the 1980s, the "domino theory" was used to justify the Reagan administration's interventions in Central America and the Caribbean region.
Article text based on the Wikipedia, licensed under the GFDL.