Kennedy's assassination 45 years ago today made it an American war.

The assassination of John F. Kennedy 45 years ago today brought an abrupt end to what his admirers called Camelot, a presidential era of glamour, intelligence, wit and possibility. But the murder had an even more profound consequence: Nov. 22, 1963, was the single most significant day in the history of the Vietnam War.

Kennedy's assassination 45 years ago today

It's not possible to know for certain how Kennedy would have managed the crisis in Vietnam had he lived. But it's clear that he was determined to prevent Vietnam from becoming an American war and that he expected to withdraw fully during a second term.

At the point Kennedy assumed office in 1961, American military involvement in Southeast Asia was limited to arms shipments and a small number of advisors. But the South Vietnamese regime of Ngo Dinh Diem was facing an increasingly potent communist insurgency and, in the U.S., pressure was building to send in ground troops.

Over the course of the year, Kennedy's advisors presented him with half a dozen or more proposals to Americanize the war. In one, Secretary of Defense Robert McNamara, Secretary of State Dean Rusk and the Joint Chiefs of Staff argued that it would be difficult to prevent "the fall of South Vietnam by any measures short of the introduction of U.S. forces on a substantial scale."

Kennedy's advisors told him that to defend the Saigon regime might take more than 200,000 combat troops. McGeorge Bundy, national security advisor, believed that committing American troops was vital. "Laos was never really ours after 1954," Bundy explained to the skeptical president, invoking another Southeast Asian nation where Kennedy had resisted intervention. "Vietnam is and wants to be."

Kennedy was not receptive. Long before becoming president, he had spoken out in Congress against the disastrous French experience in Vietnam, citing it as a reason the U.S. should never fight a ground war there. In the summer of 1961, he said he had accepted the conclusion of Gen. Douglas MacArthur, who counseled against a land war in Asia, insisting that even a million American infantry soldiers would not be sufficient to prevail. He would offer military aid and training to Saigon, but he would not authorize the dispatch of ground forces.

Over the three years of his presidency, Kennedy sometimes invoked hawkish rhetoric about Vietnam. He also increased the military advisors and training personnel there to roughly 16,000. But McNamara and Bundy both came to believe that Kennedy would not have Americanized the war -- even if the price was communism in South Vietnam.

Ngo Dinh Diem and President Eisenhower

Kennedy realized that the inability of the United States to shut down the Ho Chi Minh Trail -- the lines of infiltration and resupply from North Vietnam -- would make it impossible to defeat the insurgency. "Those trails are a built-in excuse for failure," Kennedy told an aide in the spring of 1962, "and a built-in argument for escalation." Kennedy was so dubious he declared to White House aide Michael Forrestal that the odds against defeating the Viet Cong were 100 to 1.

In early 1963, Kennedy told Senate Majority Leader Mike Mansfield, who opposed increased U.S. involvement in Vietnam, that he would begin withdrawing advisors from South Vietnam at the beginning of his second term in 1965. Kennedy disclosed the same plan to Roswell Gilpatric, his deputy secretary of Defense. But the tragedy in Dallas in November 1963 changed everything.

What happened after Kennedy's death is a familiar story. Lyndon B. Johnson ran for president in 1964, and in August of that year he used an ambiguous incident in the Gulf of Tonkin to extract an open-ended congressional authorization for military action against North Vietnam. On March 8, 1965, Johnson sent the first 3,500 Marines to Vietnam. Within months he had approved deploying 175,000 combat troops.

If Kennedy had lived, he would have enjoyed enormous advantages in 1965. In a second term, Kennedy would have been invulnerable to the electorate. He would not have had Johnson's grand liberal agenda of Great Society legislation to ram through Congress. He had established a firm practice of overruling his advisors when necessary. And he would have entered his final four years as the champion of the Cuban missile crisis, a national security accomplishment that would have dramatically strengthened his hand.

"So he does not have to prove himself in Vietnam," Bundy retrospectively argued. "He can cut the country's losses then. He can do it by refusing to make it an American war."

That Kennedy as commander in chief was not provided the opportunity to determine a different fate for the United States in Vietnam deepens the tragedy of his loss and also underscores his profound legacy, still richly relevant 45 years later: The judgment of the commander in chief, soon to be resting on the shoulders of President-elect Barack Obama, ultimately determines the difference between war and peace.

(By Gordon M. Goldstein, Los Angeles Times, November 22, 2008, Gordon M. Goldstein is the author of "Lessons in Disaster: McGeorge Bundy and the Path to War in Vietnam," recently published by Times Books.)