What political theory suggests that if one nation falls to communism, neighboring nations will follow?

The political theory that suggests if one nation falls to communism, neighboring nations will follow is known as the Domino Theory. This concept emerged during the Cold War and was used particularly to justify U.S. involvement in various conflicts, most notably in Vietnam. The idea is that the spread of communism in one country could trigger a chain reaction, leading to the fall of other adjacent countries to the same ideology, much like a row of falling dominos.

The Domino Theory reflects a broader apprehension about the potential for communism to expand and gain influence, highlighting the interconnectedness of nations in geopolitical dynamics. It played a significant role in the foreign policies of the time, influencing how countries approached military engagement and alliances. Other theories mentioned do not specifically address the spillover effect of political ideologies in the way the Domino Theory does.