Answer:
The Domino theory.
Step-by-step explanation:
A cold war policy that a communist government could lead to influence and control of other neighboring nations by communists like a row of perfectly aligned dominos would fall and this theory was called the domino theory. This theory was used by the United States government to Justify its support to a non-communist dictator of South Vietnam. This theory crumbled when communism failed to show strong foot in South eat Asia.