SEATO was formed when Australia, France, Great Britain, New Zealand, Pakistan, the Philippines, Thailand, and the United States signed the Southeast Asia Collective Defense Treaty in Manilla, the Philippines, on September 8, 1954. The treaty was proposed by the United States after Communist forces defeated France in Indochina. Its purpose was to prevent the further expansion of Communist influence in Southeast Asia. The signatory nations agreed to help defend each other -- as well as other designated nations -- against military aggression in Asia.

Despite its name, only two Southeast Asian nations were SEATO members. The Philippines joined in part because of its close ties with the United States and in part out of concern over the communist insurgency threatening its own government. Thailand, similarly, joined after learning of a newly established "Thai Autonomous Region" in Yunnan Province in South China, expressing concern about the potential for Chinese communist subversion on its own soil. Burma, Indonesia, and Malaya all preferred to maintain their neutrality, while the terms of the Geneva Agreements of 1954 signed after the fall of French Indochina prevented Vietnam, Cambodia, and Laos from joining any international military alliance. The majority of the SEATO member states were located well outside of Southeast Asia, but all had an interest in the region.

Headquartered in Bangkok, Thailand, SEATO had only a few formal functions. It maintained no military forces of its own, but the organization hosted joint military exercises for member states each year. As the communist threat appeared to change from one of outright attack to one of internal subversion, SEATO worked to strengthen the economic foundations and living standards of the Southeast Asian States. It sponsored a variety of meetings and exhibitions on cultural, religious and historical topics, and the non-Asian member states sponsored fellowships for Southeast Asian scholars.

Neither Pakistan nor France supported the U.S. intervention in Vietnam, and both nations were pulling away from the organization in the early 1970s. Pakistan formally left SEATO in 1973 because the organization had failed to provide it with assistance in its ongoing conflict against India. When the Vietnam War ended in 1975, the most prominent reason for SEATO's existence disappeared, and SEATO formally disbanded on February 20, 1976.

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This page was last updated on 01/07/2019.