The principle of collective security refers to a system where states agree to respond collectively to threats against one of their members, enhancing overall security. This concept underpins organizations like the United Nations and NATO, where member states commit to mutual defense. Collective security aims to deter aggressors by ensuring that an attack on one nation prompts a collective response, promoting a stable international order. While this principle has succeeded in various contexts, it can face challenges, such as differing national interests or the inability to respond effectively to crises, undermining its efficacy.