[After watching the documentar today called "The Fog Of War". I did some research online on Robert McNamara the man behind this documentary. I found this interesting article--Kevin.
Robert McNamara was Secretary of Defense during the Kennedy and Johnson administrations. He was a key architect of early U.S. policy in Vietnam and supported the U.S. military involvement. But as the war escalated yet failed to bring results, and as resistance to the war mounted at home, McNamara began to push for a negotiated solution. In 1968, after opposing further bombing of North Vietnam, he lost influence in the Johnson administration and left to become president of the World Bank. He was interviewed for this episode of COLD WAR in June 1996.
On why the United States became involved in Vietnam:
[The domino theory] was the primary factor motivating the actions of both the Kennedy and the Johnson administrations, without any qualification. It was put forward by President Eisenhower in 1954, very succinctly: If the West loses control of Vietnam, the security of the West will be in danger. "The dominoes will fall," in Eisenhower's words. In a meeting between President Kennedy and President Eisenhower, on January 19, 1961 -- the day before President Kennedy's inauguration -- the only foreign policy issue fully discussed dealt with Southeast Asia. And there's even today some question as to exactly what Eisenhower said, but it's very clear that a minimum he said ... that if necessary, to prevent the loss of Laos, and by implication Vietnam, Eisenhower would be prepared for the U.S. to act unilaterally -- to intervene militarily.