Sheehan argues we can give infrastructure support to Afghanistan without the military. But it doesn't seem that we can build anything there while the Taliban is in control. In an ideal world, I agree with Sheehan. But I think Afghanistan is like health care reform. It's complex and people don't want to know what they don't want to know.
Here's a good read on why we can't let Afghanistan fail:
Skeptics of Obama’s Afghanistan policy say that the right approach is to either reduce American commitments there or just get out entirely. The short explanation of why this won’t work is that the United States has tried this already—twice. In 1989, after the most successful covert program in the history of the CIA helped to defeat the Soviets in Afghanistan, the George H. W. Bush administration closed the U.S. embassy in Kabul. The Clinton administration subsequently effectively zeroed out aid to the country, one of the poorest in the world. Out of the chaos of the Afghan civil war in the early 1990s emerged the Taliban, who then gave sanctuary to al Qaeda. In 2001, the next Bush administration returned to topple the Taliban, but because of its ideological aversion to nation building it ensured that Afghanistan was the least-resourced per capita reconstruction effort the United States has engaged in since World War II. An indication of how desultory those efforts were was the puny size of the Afghan army, which two years after the fall of the Taliban numbered only 5,000 men, around the same size as the police department of an American city like Houston. We got what we paid for with this on-the-cheap approach: since 2001 the Taliban has reemerged, and fused ideologically and tactically with al-Qaeda. The new Taliban has adopted wholesale al-Qaeda’s Iraq playbook of suicide attacks, IED operations, hostage beheadings, and aggressive video-based information campaigns. (The pre-9/11 Taliban had, of course, banned television.)
Why should we believe that the alternative offered by the Obama administration—committing large numbers of boots on the ground and significant sums of money to Afghanistan—has a better chance of success? Read the rest here