AMIAN, Afghanistan — Hussein Jan, a 51-year-old farmer, tossed a stone into a shallow pit dug on a slope above this town. "They shot us here, 76 people, they killed everyone, and only I survived," he said. "With me there were 11 people from my village, most of them relatives, and I alone survived," he said. He laughed, tipping his head back, but his face suddenly twisted into a grimace of terrible pain. In tales like this, the people of the Bamian region have been counting their dead since they returned to this fabled valley seven months ago, after the...