An aggressive campaign of American drone strikes in the Pech over the past year and a half has been instrumental, Afghans and American officials say. They assert that the strikes have devastated the insurgent networks, focusing on Qaeda leaders and their facilitators. The recent targeted killing of the Nuristan shadow governor, Dost Muhammad Khan, considered one of the top Taliban leaders in the country and a crucial asset for Al Qaeda, was a high point of the campaign.

More than American air power, with its looming expiration date next year, is in effect here, though. Analysts and officials also say that the Afghan approach to policing the area has been a strong point. While the Americans consolidated on one main base and a few outposts, the Afghans have set up more than a dozen new outposts and checkpoints farther into the valley. Their aim is focused: securing the main road that runs through the Pech through Nangalam and keeping it open for the first time in nearly 10 years.

The Afghan National Army has also notably improved in the intervening two years, the visiting Americans noted.

“The A.N.A. we left in this valley are not the A.N.A. here right now,” said Sgt. Merle Powell, who, like others, believed the Afghans would be overrun in a matter of weeks after the American departure.

What is less clear is how big a role deals worked out with the insurgents might play in pacifying the area.

While most Afghan officers were reluctant to talk about any such compromises in the Pech Valley, one general — Gen. Nasim Sangin, the executive officer of the Second Brigade of the Afghan Army’s 201st Corps — briefly discussed a larger example of restrained military ambition, in the nearby Korangal Valley. General Sangin said the army had decided not to mount operations there because it lacked the resources and the loss of life would hardly be worth it.

“The Korangal, it is a good place for the insurgents,” he said. “It is not a good place for us.”

The Americans say they have no evidence of arrangements between the security forces and the insurgents, but recognize that the Afghans may not have the capacity to go after particularly remote areas.