Following the end of the Second War War, and with the onset of the Cold War between the United States and the Soviet Union, the U.S. initiated a series of treaties with groups of countries in particular regions of the world intended to bind these countries together for their common defense. Known as “collective security arrangements,” the concept of such alliances goes back to ancient times. With the escalation in hostilities between the U.S. and the U.S.S.R., however, the United States placed a great deal of importance on such treaties in its effort at containing the Soviet Union. Such was the fear of the spread of communism throughout the world, that the formation of U.S-led alliances became one of this country’s highest priorities. In Western Europe, which faced the most direct threat from large Soviet armies along the border separating the two Germanys, the United States worked with Great Britain and other friendly countries to form the North Atlantic Treaty Organization (NATO). Article V of that treaty stated that an attack upon any one member of NATO would be considered an attack on all members of the alliance, which would compel all members to come to the defense of the country under attack.
In addition to NATO, which remains an active alliance, other examples of collective security arrangements that the United States forged during the 1950s were the Central Treaty Organization (CENTO), comprising, in addition to the U.S., Great Britain, Turkey, Iran, Iraq, and Pakistan, and the Southeast Asian Treaty Organization (SEATO), which included the U.S., France, Great Britain, Australia, New Zealand, Pakistan, Thailand and the Philippines. The latter of these organizations, SEATO, was of particular and obvious relevance during the wars in Vietnam. The membership of both the United States and France in SEATO bound these countries in what was then known as French Indochina, which included Vietnam, Laos and Cambodia, and which were the focal point of major Cold War conflicts. Following the 1954 French defeat at Dien Bien Phu in northern Vietnam, the United States replaced France in that region as the principal country seeking to contain the spread of Soviet and Chinese-inspired communism in the region. While France’s presence in Southeast Asia had been strictly imperial in nature, however, the growing U.S. role there was focused entirely on containing communism.
As the U.S. role in Vietnam grew during the 1950s and, especially during the 1960s, the United States appealed to its allies in the region for assistance. Consequently, SEATO members like Australia, Philippines and Thailand would become important parts of the U.S. military and political effort at protecting South Vietnam from North Vietnam, which was heavily supported by the Soviet Union and China. Australia sent troops to fight alongside the U.S. and the Army of South Vietnam, and the U.S. made very heavy use of military installations in Thailand and the Philippines in support of military operations in Vietnam. In fact, Clark Air Force Base and Subic Bay Naval Base in the Philippines were considered the U.S.’ most important installations in the Asia Pacific region. In addition to the bases in those countries, the U.S. also used its security arrangements with Japan to use military bases there, for example, the naval installation at Yokosuka, and at Okinawa and the U.S. territory of Guam. In short, collective security arrangements were extremely important to the U.S. war effort in Vietnam, as Soviet and Chinese military support for North Vietnam was to that country.