Steve Coll outlines the actual choice Obama is confronting:

Look, there's no chance that the Obama administration or the international community is just going to pull the plug on Afghanistan and walk away. There is a commitment to do the hard work, to prevent the Taliban from taking control of the Afghan government, from destabilizing all of South Asia, from destabilizing Pakistan.

So the question is not stay or go. The question is, are more American troops part of the solution, or are more American troops part of the problem?

But shouldn't we try to avoid starting arguments by ruling out one obvious, if clearly perilous answer (among several)? Steve actually has a response to that:

I wonder if there is enough clarity, even inside the Obama administration, about exactly what security interests we're really fighting for here. I think that there are two.

One the president articulates all the time, and I think he's correct about it: It's a vital national security issue for the United States to defeat or disable or reduce Al Qaeda to the point where it can no longer carry out disruptive attacks against the United States or important allies of the United States.

But Al Qaeda isn't in Afghanistan. Al Qaeda is on the border. You can argue that an American presence in Afghanistan is vital to continue to prosecute that important campaign. But that's only one of the two reasons that this war matters.

The other is that the United States has a vital national security interest in a stable, modernizing South Asia. Pakistan, India, all of South Asia -- a billion and a half people are on the cusp of joining modern Asia in a march to prosperity, political normalcy and stability.

If Pakistan blows up, if the Taliban succeed in radicalizing local populations, then this region will be chronically unstable for years to come.

And why does that matter to the United States? Not least because there are more than 100 nuclear weapons already finished and extant in this region. But this is a region that, like Southeast Asia and Latin America, has the opportunity to stabilize, gel, integrate economically and march toward modernity.

The Taliban are essentially all that stands in the way of that project. It's more complicated than that, because the Taliban are a creature of dysfunctional Pakistani security services and lots of other unsolved problems. But the United States has a vital national interest in making sure that the Taliban do not destabilize South Asia.

And Afghanistan is not the only place where that contest is going to be carried out. And it is not a contest that is only military. It's a complicated transnational contest. But it is of vital interest I think to this country, and it does require substantial patience and investments.

My worry is simply that, however lovely this would be, it could be undoable. Undoable for cultural, political, religious, regional reasons. And that there is always the potential for continued enmeshment to deepen and spread the friction between the West and Islam. I fear we are defining a vital national interest on a battlefield we can never control or even fully understand.

Maybe I'm being too pessimistic (I was about the military potential of the Iraq surge to quell the population). Sam Roggeveen rightly argues that the devil is in the details, and that each decision should be empirically based and that the record of Western intervention in the developing world is not as bad as it might seem. He's right that to stick to pure pessimism as some kind of doctrine is not conservative at all. I just get queasy at the vastness and complexity of the neo-imperial task, the potential for even more blowback, and the knowledge that the power trying to accomplish this is ... well, bankrupt. Its major global rival, China, can sit back, enjoy the benefits if America wins, and enjoy America's accelerated decline if America loses.

Isn't there a point at which you have to conclude: not worth it?

(Hat tip: AtlanticWire)

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