Remember the war in Afghanistan? You know: It was the “good war,” fought in response to al Qaida’s attack on 9/11 and the Taliban’s refusal to turn them in, and subsequently justified by 1) the need to prevent future terrorist “safe havens,” 2) the desire to liberate Afghan women, 3) the imperative to bring democracy and modern governance to an underdeveloped tribal society and 4) as always, the need to preserve American “credibility.”

Writing on The New Yorker’s website, reporter Dexter Filkins warns that our long and costly effort there is likely to be a failure. We’re getting out, he says, but there is little sign that we will leave behind a properly functioning Afghan state. He notes that neither President Obama nor Mitt Romney is saying much about the war in this campaign (in part because there is about an angstrom’s worth of difference in their respective positions). But he says “You can bet that, whoever the president is, he’ll be talking about it after we’re gone.”

Three points. First, it is not really news to hear that our Afghan project is failing, because the effort to impose a centralized state from the outside was probably doomed from the start. It’s possible that a focused international effort from 2002 onward would have succeeded (and especially if the geniuses in the Bush administration hadn’t taken their eye off the ball in order to invade Iraq), but the odds are against it. Plenty of people have been warning for years now that this war was going to end up a failure, which is why some of us opposed Obama’s decision to escalate the war in 2009 and called for disengagement instead.

Second, even if Filkins’ pessimism is right, it is not clear why the next president will want or will have to spend a lot of time worrying about Afghanistan. If Afghanistan were truly a vital strategic interest, it wouldn’t be all that hard to convince Americans to pony up the resources to stay. But the fact is that Afghanistan isn’t a vital interest: it’s a land-locked and impoverished country thousands of miles from our shores. The only reason that we went there in the first place is because a handful of misguided crackpots decided to hide out there, and subsequently got very lucky in staging a dramatic attack on U.S. soil. Once they were scattered and/or killed, Afghanistan reverted to being the strategic backwater it has always been. The American people understand this, yet Obama had to concoct a face-saving strategy of escalating first in order to withdraw later. If the next president — whoever it is — is smart, he’ll spend as much time worrying about Afghanistan as Carter and Reagan spent worrying about Vietnam. Which is to say, hardly any.

Third, this whole sad episode should really be seen as a colossal failure of the American national security establishment. The futility of the Afghan campaign was apparent years ago, and we’ve heard plenty of testimony from returning soldiers, diplomats, and aid workers that the International Security Assistance Force

effort wasn’t likely to work. Even those who continued to defend the effort usually had to admit that success was going to require a decade or more of additional commitment and hundreds of billions of dollars in additional aid. Yet our national security apparatus couldn’t reach the conclusion to withdraw without first escalating the war, and without wasting more soldiers’ lives and a few hundred billion more dollars.

I’ve offered my own thoughts on why it’s hard to end costly wars here; today I’ll simply say it’s even harder when the culture of the national security establishment rewards hawkish postures and tends to view anyone who counsels moderation or prudence as some sort of weak-willed idealist. Nothing does more than hard-headed and realistic assessments of the costs and benefits of alternative course of action, even when the writing was on the wall a long time ago.

Stephen M. Walt is a professor of international relations at Harvard University.