In the years since Sergeant Bergdahl’s capture by the Taliban, and even more since his release last week in a contentious prisoner exchange for five Taliban fighters, much has been written suggesting that he was a misfit soldier in something of a misfit platoon that stumbled through its first months in Afghanistan and might have made it too easy for him to walk away, as his fellow soldiers say he did.

Indeed, an internal Army investigation into the episode concluded that the platoon suffered from lapses in discipline and security in the period before Sergeant Bergdahl — a private first class at the time who was promoted while in captivity — disappeared into Paktika Province, two officials briefed on the report said…

To pass the time on long trips outside the wire, some in the platoon would make wagers on when a roadside-bomb attack might come. “We’d take bets on this one stretch of road, how many I.E.D.s are we going to hit, or who is going to get hit,” said Josh Cornelison, the platoon’s medic, describing it as the sort of humor that came only from soldiers who have already been through a bomb blast. Mr. Cornelison was one of several members of the platoon who spoke about the deployment. He and another soldier who spoke on the record have been discussing Sergeant Bergdahl widely in the news media. But other members of the unit who spoke on the condition of anonymity offered similar accounts.