Could America Leave Afghanistan Completely?

Mark Thompson wonders how many troops we will remain:

Early suggestions that the 2015 U.S. troop presence in Afghanistan could be as high as 20,000 to 30,000 have shrunken to smaller options in the 2,500-to-10,000-troop range. Plainly, the White House is fed up with the corrupt Afghan government. It also views a large troop presence as a drain on its budget, as former Army officer and ex-NSCer Doug Ollivant pointed out Monday on Battleland.

David Barno believes that pulling all troops out is a possibility:

Even though the Zero Option is not the best choice to protect American long-term regional interests, it certainly remains on the table. Overreach on Karzai's part could easily sour prospects for any sort of enduring U.S. military presence.