9. The Domino Theory
The Domino Theory was a Cold War-era geopolitical concept suggesting that the fall of one nation to communism would lead to a chain reaction, causing neighboring countries to follow suit. This theory significantly influenced U.S. foreign policy, particularly during the Vietnam War, where it was used to justify American intervention in Southeast Asia (history.com). However, the theory’s validity has been widely discredited, as the anticipated widespread spread of communism did not occur.
