What term describes a system in which a group of nations acts as one to preserve the peace of all?

• A. Isolationism
• B. Balance of Power
• C. Collective Security
• D. Multilateral Diplomacy

Answer: (C)

Collective security is the idea that many nations join together and act as one to preserve peace for everyone. In this system, aggression against one member is treated as aggression against all, and the group commits to a coordinated response—often through an international organization or treaty—to deter and, if needed, stop the threat. This unity raises the costs for any aggressor and relies on shared legitimacy and collective action.

This differs from isolationism, which would mean stepping back from international involvement rather than binding states to defend each other. It also differs from the balance of power approach, which focuses on shifting alliances and power dynamics to prevent any one state from dominating, rather than a formal, agreed defense commitment to all members. Multilateral diplomacy involves many countries working together in talks, but it does not by itself obligate a collective defense response.

So, the term that best describes a system where a group of nations acts as one to preserve peace for all is collective security.