What is the term used to describe a security arrangement where a group of nations agrees to respond collectively to threats against any member?

The term that describes a security arrangement where a group of nations agrees to respond collectively to threats against any member is known as collective security. This concept is grounded in the idea that an attack on one member is considered an attack on all, thereby obliging all members to come to the defense of the affected nation. Collective security aims to deter aggression and maintain peace and stability through cooperative measures among nations.

This understanding aligns with historical practices seen in organizations like the United Nations, where member states commit to collective action against aggression and uphold international peace. Collective security differs from other terms in that it emphasizes the prevention of conflict through a unified response to threats rather than focusing only on relationships between specific allies or predetermined military agreements.

The other options, while related to aspects of international relations, do not fully capture the essence of responding to threats in a way that encompasses multiple states working together in a broader context. For example, mutual defense typically refers to agreements specifically between two nations to support each other, while an alliance system usually focuses on formalized partnerships among a limited number of countries without a universal commitment to peace. Collective action, on the other hand, is a more general term that can apply to various types of cooperative efforts, not specifically to the nature of military or