Which U.S. foreign policy was characterized by the phrase "domino theory"?

The phrase "domino theory" is intrinsically linked to the U.S. policy of containment, particularly in Southeast Asia during the Cold War. This theory suggested that the spread of communism in one nation could trigger a chain reaction, leading neighboring countries to also fall under communist influence like a row of falling dominos. This belief significantly influenced U.S. foreign policy decisions after World War II, especially in countries such as Vietnam, where the U.S. sought to prevent the spread of communism by intervening militarily and diplomatically.

The context of containment centered around the broader strategy of opposing the influence of the Soviet Union and its allies. By viewing the geopolitical landscape through the lens of this theory, U.S. policymakers justified military involvement and support for anti-communist regimes, believing that failure to act would lead to further expansions of communism. Thus, the core idea of the "domino theory" reinforced the motivations for U.S. engagement in Vietnam and other Southeast Asian countries during the Cold War era.

In contrast, the other options do not align with the concept of the domino theory. Isolationism in the 1920s reflected a retreat from global engagements, whereas expansionism in Latin America was focused on increasing U.S.