In 1965, General Westmoreland, commander of US forces in Vietnam, requested more ground troops from President Johnson. He also expressed his support for "Operation Rolling Thunder," a sustained bombing campaign against the North Vietnamese which represented a major expansion of the Vietnam War.

In response, Clark Clifford, one of Johnson's most senior and trusted advisers, argued against such an escalation. In a short letter to the President he said that US ground forces in South Vietnam should be kept to the absolute minimum. Anything more than that, argued Clifford, could be construed as a concerted attempt by the United States to win the war on the ground instead of simply defending an ally, which was, after all, the main rationale for American involvement in Vietnam.

He then went on to say that escalation could lead the United States into a quagmire. Clifford feared that the potentially open-ended commitment that this would entail would simply lead to the provision of more and more troops without any realistic hope of ultimate victory. Sadly, Clifford's wise counsel was ignored, and his predictions proved to be all too correct.