Collective security

Collective security is an arrangement in which states treat aggression against one member as a concern for all members. It seeks to deter or stop aggression through a shared response.

United Nations Security Council: The United Nations body with primary responsibility for maintaining international peace and security. It can authorize collective measures, though vetoes can block action.
Concert of Europe: A system of consultation among major European powers established after the Napoleonic Wars. It offered an early model of joint action to preserve peace, though not universal security.
Balance of power: A distribution of power among states that prevents any one state from dominating the others. It seeks stability through counterweights, rather than a common response to aggression.
Korean War: A war from 1950 to 1953 between North Korea and South Korea, involving United Nations forces and China. A Security Council resolution enabled a military response while the Soviet Union was absent.
Responsibility to protect: A principle that states must protect populations from mass atrocities and that the international community should respond when they fail. It reframes protection from aggression as a responsibility extending to populations facing atrocities.
United Nations Charter: The treaty that established the United Nations and sets out its purposes, powers, and rules. Its provisions prohibit force and authorize enforcement measures against threats to peace.
League of Nations: An international organization founded in 1920 to promote cooperation and prevent war. Its Covenant gave the first broad institutional form to collective security.
Isolationism: A foreign-policy approach that limits a state’s involvement in international affairs. It rejects the sustained external commitments collective security requires.
Suez Crisis: The 1956 confrontation after Egypt nationalized the Suez Canal and Britain, France, and Israel invaded Egypt. The United Nations helped secure a ceasefire when Security Council action was blocked.
Sovereignty: The authority of a state to govern its territory and conduct its affairs without external control. Collective action can constrain sovereignty when a state threatens international peace.

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