Fred Kaplan is ambivalent about what to do in Afghanistan…and makes great arguments against all options, which I fully endorse. There is one argument for continuing the fight that I would add, however:
Pakistan. If the U.S. doesn’t remain engaged in Afghanistan, the civilian government in Pakistan–already an incredibly shaky enterprise–will probably fall. Certainly, the Pakistani Army will be further empowered and will likely bolster its support for its Taliban allies in order to prevent India from establishing a foothold in Kabul. The possibility of a Pakistani Army coup scares the bejeezus out of expert like Bruce Riedel. It’s not impossible that it would be an Islamist takeover. (Indeed, it’s happened before: the coup that brought Zia al-Haq to power in the 1980s.)
The scariest national security problem we now face is the prospect of al-Qaeda-linked jihadis controlling the Pakistani nuclear arsenal. Like Fred Kaplan, I’m not optimistic that the U.S. effort can succeed in Afghanistan. But the notion that a U.S. withdrawal might empower the religious extremists in the Pakistani military does give me pause.