Formation of SEATO

Date: September 8, 1954 • Location: Intramuros, Philippines

Eight nations signed a collective-defense treaty in Manila to create the Southeast Asia Treaty Organization (flag pictured), modelled on NATO.

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.