"Collective security" in international relations refers to an agreement among nations to respond collectively to threats or acts of aggression against any member state. This concept emphasizes mutual defense, where an attack on one is considered an attack on all, aiming to deter potential aggressors. Collective security mechanisms often manifest in alliances and organizations, such as the United Nations or NATO, which establish protocols for cooperation and intervention. The principle fosters stability and peace in the international system by promoting collective responsibility, although challenges arise when member states disagree on the appropriate response to threats.