Mutual defense is a security arrangement where two or more parties agree to support each other in case of an attack. This agreement can be formalized through treaties or alliances, ensuring that if one member is threatened, the others will come to its aid. A well-known example of this is NATO, where member countries commit to collective defense. The principle of mutual defense promotes stability and deterrence, as potential aggressors may think twice before attacking a member of a defensive alliance. This concept is rooted in the idea that collective security is more effective than individual efforts, fostering cooperation among nations.