Question

Which theory did four U.S. presidents use to justify U.S. participation in the Vietnam War?

domino theory

solitary confinement

bridge against communism

monopoly theory

Answer 1

The theory that American presidents used to justify US participation in the Vietnam War was the domino theory.

Step-by-step explanation:

The Domino Theory established that if a country entered a certain political system, it would drag others from its area towards that same ideology.

During the Vietnam War, framed in the context of the Cold War, this theory was used to predict what would happen if South Vietnam fell against communism.

Answer 2

They used the domino theory. It claimed that if Vietnam became a communist country, others will follow, similar to dominoes falling down.