But U.S. officials stressed that none of the detainees at that point offered up the real identity of the courier. “All we had was the nom de guerre,” said the U.S. official. To one counterterrorism expert who has sharply criticized the CIA’s interrogations, the failure of any of the high-value detainees to provide the identity of the courier raises fresh questions about the value of the information the agency was receiving from enhanced interrogations.

“They waterboarded KSM (Khaled Sheikh Mohammed) 183 times and he still didn’t give the guy up,” said one former U.S. counterterrorism official who asked not to be identified. “Come on. And you want to tell me that enhanced interrogation techniques worked?”

It is possible that neither Qahtani nor Mohammed knew the true identify of bin Laden’s trusted courier, although that would appear to contradict the U.S. official’s description of him as Mohammed’s “protégé.”