Just a week before, a different platoon in the battalion had hit a mine while accompanying the Afghan police along a dirt road. Some soldiers wondered whether the police had led the Americans into a trap. That possibility was quickly ruled out, because the police were in as much danger as the soldiers. But jitters remained.

“Everyone knows there is one way in and one way out,” one squad leader said. “I don’t like it.”

They call it a training mission, but for the soldiers of the 1-87, their work in Kunduz Province in northern Afghanistan is much more than that. Over a yearlong deployment that started in the spring, the battalion, part of the 10th Mountain Division, will not only try to hone the combat skills of the local police — a ragtag group of illiterate young men and aging fighters — but also accompany them into the most contested hamlets in the region.

The goal, a centerpiece of the American strategy to help the Afghan government stand alone, is to show skeptical Afghans that their police can keep them safe. But the unspoken first step in that strategy is getting the American soldiers themselves to trust the police.

In their first weeks in Afghanistan, the soldiers of the 1-87 would have to settle for something approaching faith.

The Afghan National Police have long been considered the weakest rung of the Afghan security forces, often lacking proper training, equipment, commitment and ethics, American commanders say. More important, American commanders worry that some police officers — whether willingly or under duress — conspire with insurgents.