The role of the United States in the Vietnam War began after World War II and escalated into full commitment during the Vietnam War from 1955 to 1975.
Feb 1965 - Operation Rolling Thunder begins
In 1961 the new administration of President John F. Kennedy remained essentially committed to the bi-partisan, anti-communist foreign policies inherited from the administrations of Presidents Truman and Eisenhower. During 1961, his first year in office, Kennedy found himself faced with a three-part crisis: The failure of the Bay of Pigs invasion in Cuba; the construction of the Berlin Wall by the Soviets; and a negotiated settlement between the pro-Western government of Laos and the Pathet Lao communist movement. Fearing that another failure on the part of the U.S. to stop communist expansion would fatally damage U.S. credibility with its allies, Kennedy realized, "Now we have a problem in making our power credible... and Vietnam looks like the place." The commitment to defend South Vietnam was reaffirmed by Kennedy on May 11 in National Security Action Memorandum 52, which became known as "The Presidential Program for Vietnam". Its opening statement reads:
U.S. objectives and concept of operations [are] to prevent communist domination of South Vietnam; to create in that country a viable and increasingly democratic society, and to initiate, on an accelerated basis, a series of mutually supporting actions of a military, political, economic, psychological, and covert character designed to achieve this objective.
Kennedy was intrigued by the idea of utilizing United States Army Special Forces for counterinsurgency conflicts in Third World countries threatened by the new "wars of national liberation". Originally intended for use behind front lines after a conventional invasion of Europe, Kennedy believed that the guerrilla tactics employed by Special Forces would be effective in the "brush fire" war in South Vietnam. He saw British success in using such forces during the Malayan Emergency as a strategic template. Thus in May 1961 Kennedy sent detachments of Green Berets to South Vietnam to train South Vietnamese soldiers in guerrilla warfare.