noun
domino theory
Cold War-era political theory that if one country falls to communism, neighboring countries will follow like a row of dominoes.
ドミノ理論は冷戦時代のアメリカの外交政策に大きな影響を与えた。
The domino theory greatly influenced American foreign policy during the Cold War.
From English 'domino theory'. The term was popularized during the Cold War.