The pact with the Shinwari tribe would complement the reconciliation effort. It echoes a similar phenomenon that unfolded in the Iraq war beginning in late 2006, which ultimately contributed to a substantial drop in violence there. In Iraq, tribal leaders from the country’s Sunni minority rebelled against Al Qaeda of Mesopotamia and joined forces with the Americans. The phenomenon was known as the Sunni Awakening.

But no one expects to be able to duplicate the scale of the Iraq effort, because in many parts of Afghanistan the Taliban have not only intimidated or killed local tribal leaders but insinuated themselves into the very fabric of the hierarchies of the tribes.

By contrast, in this part of Afghanistan tribal loyalties are strong and the tension between the Shinwaris and the Taliban longstanding. The conflict came to a head last July, when two Shinwari elders  Mr. Niaz and Malik Usman  insisted that a local Taliban commander named Kona stay away from a group of Afghan engineers who were building a dike in their valley. When Kona’s men kidnapped two of the engineers, the Shinwari elders decided they had had enough.

In a confrontation that followed, members from the two Shinwari subtribes killed a senior Taliban commander who had come from Pakistan and chased Kona back across the border. After that, Mr. Niaz and Mr. Usman set up a local militia to keep the Taliban out of the valley, called Momand.

“The whole tribe was with me,” Mr. Niaz said in an interview in November. “The Taliban came to kill me, and instead we killed them.”

The dispute also had an economic element. Many Shinwaris make their livings by smuggling across the nearby Pakistani border. According to some tribal members, the Taliban had tried to take over the Shinwaris’ business and its smuggling routes.

Image Shinwari elders united against the Taliban on Wednesday in a pact set in Jalalabad, Afghanistan. Credit... Adam Ferguson for The New York Times

The dispute caught the attention of American Special Forces units, who descended into the Momand Valley on helicopters and offered help to the local Shinwaris. The Americans gave them ammunition and food, they said.