But it is difficult for anyone, let alone the president, to think of Afghanistan as the good war anymore. Even after an eight-year American military commitment, Afghanistan still resembles a failed state with the Taliban resurgent. Everything from the flagrant ballot stuffing that destroyed the credibility of President Hamid Karzai's apparent re-election to the military morass compellingly described by my colleague David Wood has turned the latest Afghan War into Obama's first full-fledged foreign-policy crisis.

The dilemma facing the best and the brightest of the Obama administration is in many ways reminiscent of the predicament that confronted Lyndon Johnson in early 1965 as he found himself staring bleakly at a fork in the road in Vietnam. (National security adviser McGeorge Bundy actually wrote a so-called "fork in the road" memo to Johnson in late January 1965 in which he stated that continuing a merely advisory mission "can only lead to disastrous defeat.") During an off-the-record meeting with reporters at roughly the same time, Johnson likened himself to a man standing on a newspaper in the middle of an ocean. If he leaned left or right, he said, "I'll topple over." But the status quo was equally dangerous because, as LBJ put it, "If I stay where I am, the paper will be soaked up and I'll sink slowly to the bottom of the sea."

Johnson, of course, made the wrong decision – the first American combat troops of the war, two Marine battalions totaling 3,500 men, splashed ashore at Danang on the morning of March 8, 1965. As Stanley Karnow tells it in Vietnam: A History, "They rushed onto the beach...to be greeted by grinning Vietnamese girls distributing garlands of flowers and a poster proclaiming, 'Welcome to the Gallant Marines.'" By the end of 1965, American troop levels in Vietnam had increased by more than sixfold to 184,000 men. What had begun as a training mission to prop up the weak government of South Vietnam ended as the most tragic debacle in American military history.

Ever since the last helicopter lifted off from the besieged American embassy in Saigon in 1975, citing Vietnam parallels has become a way to stifle debate over other American military commitments. Just the expression, "It's another Vietnam," seems to prejudge the argument. This is unfortunate because there are contemporary lessons that can be drawn from the Johnson administration's Vietnam decision-making in early 1965 without automatically concluding that Afghanistan is a lost cause.

History is not algebra: There are no unalterable patterns or rules. And there are, to be sure, significant differences between Vietnam and Afghanistan. The instability of nuclear-armed Pakistan and its porous border with Afghanistan seems a far more realistic threat than 1960s fears of a Communist long march through Asia. America now depends on a professional, albeit over-stretched, military rather than the draft. And it is hard to think of a Democratic president less like the contained, understated Barack Obama than the volcanic Lyndon Johnson.

But there are also suggestive parallels between Vietnam in 1965 and Afghanistan now. The choices facing America in Vietnam were bleak – gradually pull out in the face of an almost-certain North Vietnamese victory; depend on the unlikely notion that saturation bombing alone would bring Hanoi to the negotiating table; or escalate with ground troops. A weak and incompetent civilian government in Saigon – which might make Karzai look like a statesman in comparison – was ousted in May 1965 by a military coup led by Air Marshal Nguyen Cao Ky and Gen. Nguyen Van Thieu. And on the political front, the Johnson administration knew that it would be vulnerable to Republican attacks if it retreated – little more than a decade earlier Democrats were reeling from right-wing accusations that they had deliberately handed over China to the Communists.

The decision to Americanize the Vietnam War was made incrementally over a six-month period in 1965 after dozens of meetings, volumes of memos, but little long-term strategic thinking. As John Prados writes in Vietnam: The History of an Unwinnable War, 1945-1975, "The process (was) one of ambivalent men marching into a conflict that they did not understand in pursuit of goals they had failed to clarify."

The expansion of the air war over North Vietnam meant that the U.S. air base in Danang was vulnerable to Vietcong attack. To protect Danang, Gen. William Westmoreland called for insertion of 3,500 Marines, later insisting that he did not see this temporary measure as "the first step in a growing American commitment." In a taped conversation in March 1965, LBJ confided to Georgia Sen. Richard Russell, "I'm scared to death of putting ground forces in, but I'm more frightened about losing a bunch of planes from a lack of security...I think everybody's going to think, 'We're landing the Marines. We're off to battle.'"

But just a month later, Johnson approved sending two more Marine combat battalions to Vietnam – and, more importantly, allowed them to mount operations against the enemy instead of merely guarding bases. "With that decree, the Americanization of war was arguably an accomplished fact," writes Gordon Goldstein in Lessons in Disaster: McGeorge Bundy and the Path to War in Vietnam. "Not only was the Kennedy no-combat-troop policy decisively reversed, the mission of U.S. forces was now active participation in offensive counter-insurgency operations."

There is a widespread theory that Johnson erred by not listening to naysayers in Congress like Senate Majority Leader Mike Mansfield and within his own administration like George Ball, the under secretary of State. And, in fact, Vice President Hubert Humphrey was barred from major foreign-policy meetings for a year because of his vociferous expression of dovish views.

But recent histories suggest that Ball, in particular, may have been more than just an in-house devil's advocate. According to Prados in his Vietnam War history, "Transcripts of the Oval Office and NSC meetings show LBJ working much harder than would be consistent with a devil's advocate model, even baiting Ball to draw him out. Either LBJ was making a record or he truly hoped George Ball would convince others in the room."

If there is a moral to come out of the fatally flawed 1965 Johnson administration decision-making, it probably is the innate bias of virtually all presidential advisers for action over inaction, for trying something new rather than stumbling forward with an inadequate status quo. The do-something ethos is an occupational hazard with presidents, regardless of party or ideology. And, sadly, that probably applies to Afghanistan as much as Vietnam.