What term describes the fear that if one nation falls to communism, nearby nations will also fall?

The concept known as the "Domino effect" illustrates a specific geopolitical theory during the Cold War era, suggesting that the spread of communism in one nation could lead to a chain reaction resulting in neighboring nations also succumbing to communism. This metaphor likens countries to a line of dominoes: if one is knocked over, it has the potential to lead to the subsequent fall of the others, thereby expanding communist influence.

This terminology is rooted in the historical context where various conflicts, particularly in Southeast Asia, raised concerns that the fall of Vietnam to communism would lead to similar outcomes in surrounding countries like Laos and Cambodia. Hence, political leaders and strategists utilized the term to justify intervention and containment policies aimed at preventing this perceived threat.

While other options may relate to the idea of sequence or cause-and-effect, they do not convey the specific political implications and fears associated with the spread of communism that the "Domino effect" encapsulates.