Answer:
domino theory
Explanation:
The domino theory was the idea, very popular during the Cold War in the U.S., that stated that if one country fell to communism, and therefore, to the Soviet Sphere, very quickly all of its neighbors would fall to communism as well.
This was the idea behind the U.S. invervention in Vietnam. The U.S. government thought that if Vietnam fell to communism, then Laos, Cambodia, Thailand, or Indonesia would follow soon.
The Gulf of Tonkin Resolution (1964) provided congressional support for president Lyndon B. Johnson to take any measure he deemed necessary to keep stability, and American Interests in Southeast Asia. In other words, this resolution gave permission to Johnson to launch the military intervention in Vietnam.
