Southeast Asia Treaty Organization

The Southeast Asia Treaty Organization (SEATO) was an alliance organized pursuant to the Southeast Asia Defense Treaty to oppose the growing communist influence in Southeast Asia. The United States, the United Kingdom, France, Australia, New Zealand, Thailand, the Philippines, and Pakistan signed the treaty and accompanying Pacific Charter in Manila on September 8, 1954. The treaty became operative in February 1955 and bound the signatories to mutual aid to resist armed attack or subversion; an armed attack on one signatory was interpreted as a danger to all.

Headquartered in Bangkok, SEATO relied on the military forces of member nations rather than commanding its own standing forces, as did the NORTH ATLANTIC TREATY ORGANIZATION. In its first few years of operation, SEATO's effectiveness was not tested, but at the beginning of the 1960s, conflicts in South Vietnam and Laos challenged the strength of the alliance and ultimately found it lacking. France withdrew from military cooperation in SEATO in 1967, and Great Britain refused active military cooperation in the Vietnam conflict. Moreover, a 1960s dispute between Pakistan and India further undermined the efficacy of the alliance: Pakistan drew closer to communist China, while the United States provided aid to India.

In 1972 Pakistan completely withdrew from the alliance; in 1974 France suspended its membership payments. In September 1975 the signatories decided to phase out the operations, and SEATO was formally dissolved on June 30, 1977. The collective defense treaty remains in effect, however.