Indeed, modern Pashtun history is, in part, one of backlashes against overambitious modernization efforts that lacked local “buy-in.”

The American military has become far more sensitive to Afghan sensibilities in the last few years, and there are some first-rate commanders on the ground who cooperate well with local Pashtun leaders. That creates genuine stability. But all commanders cannot be above average, and a heavier military footprint almost inevitably leads to more casualties, irritation and recruitment for the Taliban.

One of the main arguments for dispatching more troops is the terrorist threat from Al Qaeda. But Steven Simon, a National Security Council official in the Clinton years who is now a terrorism expert at the Council on Foreign Relations, notes that there may be more Al Qaeda fighters in Pakistan, Yemen and perhaps Somalia than in Afghanistan.

“I’m skeptical that the war in Afghanistan is going to solve the Al Qaeda problem,” he said.

That’s not to say we should pull out, and it’s a false choice to suggest that we should either abandon Afghanistan or double down. A pullout would be a disastrous signal of American weakness and would destabilize Pakistan.

My suggestion is that we scale back our aims, for Afghanistan is not going to be a shining democracy any time soon. We should keep our existing troops to protect the cities (but not the countryside), while ramping up the training of the Afghan Army  and helping it absorb more Pashtuns to increase its legitimacy in the south. We should negotiate to peel off some Taliban commanders and draw them over to our side, while following the old Afghan tradition of “leasing” those tribal leaders whose loyalties are for rent. More aid projects, with local tribal protection, would help, as would job creation by cutting tariffs on Pakistani and Afghan exports.

Remember also that the minimum plausible cost of 40,000 troops  $10 billion  could pay for two million disadvantaged American children to go to a solid preschool. The high estimate of $40 billion would, over 10 years, pay for almost half of health care reform. Are we really better off spending that money so that more young Americans could end up spilling their blood in Afghanistan without necessarily accomplishing much more than inflaming Pashtun nationalism?