Primarily created to block further communist gains in Southeast Asia, SEATO is generally considered a failure, as internal conflict and dispute hindered general use of the SEATO military; however, SEATO-funded cultural and educational programs left longstanding effects in Southeast Asia.

President Dwight D. Eisenhower's Secretary of State John Foster Dulles (1953–1959) is considered to be the primary force behind the creation of SEATO, which expanded the concept of anti-communist collective defense to Southeast Asia.

[1] Then-Vice President Richard Nixon advocated an Asian equivalent of the North Atlantic Treaty Organization (NATO) upon returning from his Asia trip of late 1953,[4] and NATO was the model for the new organization, with the military forces of each member intended to be coordinated to provide for the collective defense of the member states.

[7] Organizationally, SEATO was headed by the Secretary General, whose office was created in 1957 at a meeting in Canberra,[8][9] with a council of representatives from member states and an international staff.

They were Australia (which administered Papua New Guinea, until 1975), France (which had recently relinquished French Indochina, by 1955), New Zealand, Pakistan (which, until 1971, included East Pakistan, now Bangladesh), the Philippines, Thailand, the United Kingdom (which administered Hong Kong, North Borneo and Sarawak) and the United States.

[16] Other regional countries like Burma and Indonesia were far more mindful of domestic internal stability rather than any communist threat,[15] and thus rejected joining it.

[17] Malaya (independence in 1957; including Singapore between 1963 and 1965) also chose not to participate formally, though it was kept updated with key developments due to its close relationship with the United Kingdom.

[15] The states newly formed from French Indochina (North Vietnam, South Vietnam, Cambodia and Laos) were prevented from taking part in any international military alliance as a result of the Geneva Agreements signed 20 July of the same year concluding the end of the First Indochina War.

[22] Canada also considered joining, but decided against it in order to concentrate on its NATO responsibilities with its limited defense capabilities.

SEATO was unable to intervene in conflicts in Laos because France and the United Kingdom rejected the use of military action.

[18] U.S. membership in SEATO provided the United States with a rationale for a large-scale U.S. military intervention in Southeast Asia.

[24][25] In addition to joint military training, SEATO member states worked on improving mutual social and economic issues.

[1] As early as the 1950s Aneurin Bevan unsuccessfully tried to block SEATO in the British Parliament, at one point interrupting a parliamentary debate between Foreign Secretary Anthony Eden and Leader of the Opposition Clement Attlee to excoriate them both for considering the idea.