Collective security

Collective security is arrangement between states in which the institution accepts that an attack on one state is the concern of all and merits a collective response to threats by all. Collective security was a key principle underpinning the League of Nations and the United Nations. Collective security is more ambitious than systems of alliance security or collective defense in that it seeks to encompass the totality of states within a region or indeed globally. The premise of a collective security arrangement is that it serves as a deterrent to aggression by committing an international coalition against any aggressor. While collective security is an idea with a long history, its implementation in practice has proved problematic. Collective security is also referred to by the phrase "an attack on one is an attack on all". However, usage of this phrase also frequently refers to Article 5 of the North Atlantic Treaty, the collective security provision in NATO's charter.