From The Pentagon Papers, New York Times,  1971:

P. 114:

Despite the tens of thousands of words in the Pentagon account of the Kennedy Administration, backed by scores of documents, the study does not provide a conclusive answer to the most vigorously debated question about President Kennedy’s Vietnam policy since his death in November, 1963: If President Kennedy had lived until 1965, would he have felt compelled by events, as President Johnson was, to undertake full-scale land war in South Vietnam and an air war against the North?

The situation, as the Pentagon account discloses, had changed significantly between 1961 and 1965. In 1961 President Kennedy was confronted by other crises—Berlin, Cuba, Laos—while he faced his harshest decisions on Vietnam, and these acted as restraints; President Johnson did not have quite the same distractions elsewhere. Too, President Diem never pushed so aggressively for American escalation as did Gen. Nguyen Khanh, the South Vietnamese leader in 1964 and 1965. Nor, as the analysts note, had other measures short of full-scale air and ground combat been exhausted, without producing success.

The Pentagon account, moreover, presents the picture of an unbroken chain of decision-making from the final months of the Kennedy Administration into the early months of the Johnson Administration, whether in terms of the political view of the American stakes in Vietnam, the advisory buildup or the hidden growth of covert warfare against North Vietnam.

“No reliable inference can be drawn,” the Pentagon study concludes, “about how Kennedy would have behaved in 1965 and beyond had he lived. (One of those who had advised retaining freedom of action on the issue of sending U.S. combat troops was Lyndon Johnson.) It does not prove that Kennedy behaved soundly in 1961. Many people will think so; but others will argue that the most difficult problem of recent years might have been avoided if the U.S. had made a hard commitment on the ground in South Vietnam in 1961.”