Originally, the plan was to leave somewhere around 15,000 American troops in Afghanistan to continue training native security forces and provide support for operations.  A few days ago, that number started drifting downward to 2,500, based on leaks from the Obama administration.  Late yesterday, Reuters reported that the actual number may be as low as … zero:

The Obama administration does not rule out a complete withdrawal of U.S. troops from Afghanistan after 2014, the White House said on Tuesday, just days before President Barack Obama is due to meet Afghan President Hamid Karzai.

The comments by U.S. Deputy National Security Adviser Ben Rhodes were the clearest signal yet that, despite initial recommendations by the top military commander in Afghanistan to keep as many as 15,000 troops in the country, Obama could opt to remove everyone, as happened in Iraq in 2011.

Asked about consideration of a so-called zero-option once the NATO combat mission ends at the end of 2014, Rhodes said: “That would be an option that we would consider.”

The main mission for an American presence in Afghanistan after the 2014 draw-down date on which Obama insists would be to keep al-Qaeda from re-establishing a presence in the region.  The Taliban, their allies, would be Hamid Karzai’s problem, which is what it was going to eventually be anyway.  The war in Afghanistan is essentially a tribal war between Pashtuns and everyone else overlaid by religious extremism, and the only resolution will be some sort of settlement that allows the tribes to live with each other.

So how can the US fight AQ to keep it from re-allying with the Taliban without having boots on the ground?  Rhodes told reporters that “There are, of course, many different ways of accomplishing those objectives, some of which might involve U.S. troops, some of which might not,” but it’s difficult to see how to do it without having some sort of military presence in the area.  Drone strikes have been effective, but only because Pakistan has been pushed into tacitly allowing them.  If we leave Afghanistan, how long will that remain the case?  I’d suspect the time could be measured in weeks, if not days, since the drone operations are a major political headache for Islamabad.  At that point, we’d have to rely on cruise missiles, which haven’t had a great track record of success against AQ in that region in the past.

One thing is certain — Obama isn’t listening to the generals on the zero-troop option, at least not how the Washington Post reports it:

Some senior military officials and analysts have pressed for a more robust force, arguing that a hasty disengagement would be reckless and could cause Afghanistan’s security forces to crumble. The United States has invested $50 billion in training and equipping the Afghan army and police.

Others say that a small, well-managed contingent could accomplish the Obama administration’s key objectives while markedly lowering the United States’ profile in a region where anti-American sentiment runs high.

“The real question is what kind of mission we’re looking at,” said a senior U.S. defense official, who spoke on the condition of anonymity to discuss ongoing deliberations. “The challenge will be the temptation to keep doing many of the things we’ve been doing.”

The zero-troop option would mean no mission at all — not just reckless disengagement but also no well-managed small contingent to accomplish “key objectives.”  Now that the Obama administration has explicitly raised this as a choice, how likely are they to conclude that leaving any troops at all is a palatable option?