Those figures were no surprise. A Government Accountability Office report for the United States Congress last March noted that 12 to 41 percent of Afghan police recruits tested positive for drug use, although that included marijuana and hashish as well as opiates. Recruits who test positive for hard drugs are dismissed, but the others are kept and given counseling. Since opiates disappear from the body quickly, however, many of the recruits could easily have avoided getting caught — apparently explaining the high number of addicts found still on the force.

The recovering policemen in the hospital, as it turned out, made no use of the many stones in the courtyard, and instead proved eager to tell their stories.

Most, like First Lt. Juma Khan Asak, 40, a border patrolman from western Afghanistan, were long-term addicts. Lieutenant Asak said he had been smoking first opium and then heroin since he was 17, long before he joined the police. Now that the eldest of his eight children was that age, he had grown concerned that his children would follow him into addiction. He turned himself in for treatment.

“I was spending 1,000 afghanis a day,” he said, “and I could no longer do my job properly.” That amount, about $20, was approximately twice his lieutenant’s salary; asked how he could afford that and support a big family, he just shrugged.

Image First Lt. Juma Khan Asak, 40, a border patrolman, said he had been smoking, first opium and then heroin, since he was 17. Credit... Christoph Bangert for The New York Times

On the western border, the major concern of the police there is interdicting drug smugglers making for Iran.