(Bonus) The Domino Theory - Wikipedia

(Bonus) The domino theory is a geopolitical theory which posits that increases or decreases in democracy in one country tend to spread to neighboring countries in a domino effect.[1] It was prominent in the United States from the 1950s to the 1980s in the context of the Cold War, suggesting that if one country in a region came under the influence of communism, then the surrounding countries would follow. It was used by successive United States administrations during the Cold War as justification for American intervention around the world. Former U.S. President Dwight D. Eisenhower described the theory during a news conference on April 7, 1954, when referring to communism in Indochina as follows: Finally, you have broader considerations that might follow what you would call the "falling domino" principle. You have a row of dominoes set up, you knock over the first one, and what will happen to the last one is the certainty that it will go over very quickly. So you could have a beginning of a disintegration that would have the most profound influences.

Moreover, Eisenhower’s deep belief in the domino theory in Asia heightened the “perceived costs for the United States of pursuing multilateralism"[3] because of multifaceted events including the “1949 victory of the Chinese Communist Party, the June 1950 North Korean invasion, the 1954 Quemoy offshore island crisis, and the conflict in Indochina constituted a broad-based challenge not only for one or two countries, but for the entire Asian continent and Pacific."[3] This connotes a strong magnetic force to give in to communist control, and aligns with the comment by General Douglas MacArthur that “victory is a strong magnet in the East."