Which Cold War policy asserted that if one country fell to communism, others in the region would follow, guiding U.S. involvement in Asia and beyond?

• A. Containment
• B. Domino theory
• C. Deterrence
• D. Massive retaliation

Answer: (B)

The main idea here is the domino theory—the belief that political changes in one country could trigger a chain reaction, with neighboring nations quickly following suit and also tipping toward communism. This view framed U.S. decision-making in Asia and beyond because officials argued that if South Vietnam fell to communism, other countries in Southeast Asia and the region would be at immediate risk, threatening broader regional security and U.S. interests.

This is the best fit because the statement focuses on a regional chain reaction of communist takeovers, not just opposition to communism in general or threats of retaliation. Deterrence and massive retaliation concern crippling threats or military responses to aggression, rather than predicting a spread of communism from one country to others. Containment is the broader aim to stop the spread of communism, but it doesn’t specify the idea of a domino-like cascade in a region. The domino theory directly captures the idea of one country’s fall leading others to follow, which is why it aligns with the described policy.