The Sixth Battalion’s march into Chak met its first ambush near the end of the first day. As the troops approached the village of Dasht-e Langar, muzzle flashes popped from a distant hillside. A mortar team responded by lobbing shells at the village, while other soldiers opened up with vehicle-mounted .50-caliber machine guns. Pretty soon everyone was firing, to the annoyance of Colonel Daowood, a rare Afghan believer in conserving ammunition.

In the midst of the firing, a truck pulled up and Sergeant Wazir hopped out. He set up a rocket on a dirt shelf, angling it in the general direction of the village, screamed a prayer and closed the circuit. The rocket burst forth, and soared — over the road, over the village, and over the mountain beyond.

That night, the men commandeered the home of a Taliban commander who had fled. Spread out on the floor, the leaders grumbled about the cold and the lack of electricity. Beneath a light bulb powered by the car battery, the officers ate what the soldiers ate: bread, a boiled potato and a single dry cube of lamb each. The men traded war stories, of a militant stripped to his underwear and forced to walk through his village and of a soldier who took up with a Taliban commander’s daughter.

The Sixth Battalion devotes much of its effort to finding the improvised bombs planted frequently along the edge of the highway and on the district roads that serve as tributaries.

At another village the next afternoon, on a dirt road several miles from Highway 1, the soldiers pounded on the door of a home until a young man emerged. When Colonel Daowood asked about improvised bombs, the youth shrugged.

“O.K.,” the colonel responded, “if any of my soldiers are killed by a mine driving down that road, I’m going to come back and kill you.”

By 3 p.m., the soldiers had found their 18th bomb of the day.

The sun was setting when they reached a village called Bambaee and met euphoric soldiers from the garrison company, stationed up the road at the district headquarters. At the edge of the village they came across a Toyota Corolla with a young man inside, nursing a gunshot wound to the leg and asking permission to drive to the provincial hospital.