Ross Douthat:

...many Taliban leaders don't necessarily see an advantage in responding to the feelers that we're apparently encouraging the Karzai government to put out, because they think they're going to win the war outright. This is not, to put it mildly, a favorable environment in which to negotiate our way out of Afghanistan. It's the kind of environment that produces temporary truces and bogus bargains, in which the Taliban pretends to be interested in power-sharing and we pretend to believe them, the better to hit that 2011 deadline for beginning troop withdrawals. And then Obama's successor will be stuck with a choice between keeping an American presence around Kabul more or less indefinitely, or pulling out and watching the "deal" that's been negotiated collapse, and the Taliban take power.

This is the case, again, for continuing to try to shift the balance of power militarily even as we keep the lines of communication open for a negotiated settlement. The point has been made, correctly, that much of David Petraeus's accomplishment in Iraq involved managing expectations, shifting goalposts, cutting deals, and redefining "victory" to mean a halfway decent outcome rather than a triumph for democracy. But these essentially political successes were inseparable from the surge's military gains, which strengthened America's hand and improved the position of Maliki's government even as they weakened the irreconcilable elements of the insurgency and incentivized more compromise-inclined elements to peel off and negotiate. And likewise, the weaker the Taliban's position in Marja or Kandahar or any other contested territory, the better the chances of a grand bargain that actually stabilizes the country, and that has some hope of holding up without a permanent American presence.

The point of a counterinsurgency campaign, in this sense, isn't to crush the Taliban once and for all. It's to create an environment in which they feel like they could be crushed, and to turn those security gains to political ends.