America's involvement in Vietnam was a matter of saving the southern half of Vietnam from the evils of communism. The United States viewed Vietnam as a moral cause; it intervened in the conflict on moral grounds - to defend American ideals, defend freedom, and stop aggression.

Policy makers deceived themselves into thinking that they could achieve their goals in Vietnam by ignoring, suppressing, or dismissing information that might have suggested otherwise. The foreign policy leaders of the Kennedy and Johnson administrations were so committed to the idea of American activism and success that they refused to consider the possibility of failure. The Vietnam disaster, therefore, was partly a result of the arrogance of the nation's leaders.

Intervention in Vietnam was the logical, perhaps even inevitable result of certain ideological assumptions. American foreign policy was wedded to a doctrine of containment that operated in response to a single, overriding imperative: the need to prevent the expansion of communism. Once involved, the US saw no other alternative to preventing the collapse of the government in South Vietnam. American policy makers believed for years that the costs of not intervening were even greater than the costs of intervention. Only after the national and international political situation shifted, could they recognize the reality of the situation and begin disengagement.