Abu Zubaydah was a mess. It was early April 2002, and the al-Qaeda lieutenant had been shot in the groin during a firefight in Pakistan, then captured by the Special Forces and flown to a safe house in Thailand. Now he was experiencing life as America’s first high-value detainee in the wake of 9/11. A medical team and a cluster of F.B.I. and C.I.A. agents stood vigil, all fearing that the next attack on America could happen at any moment. It didn’t matter that Zubaydah was unable to eat, drink, sit up, or control his bowels. They wanted him to talk.

A C.I.A. interrogation team was expected but hadn’t yet arrived. But the F.B.I. agents who had been nursing his wounds and cleaning him after he’d soiled himself asked Zubaydah what he knew. The detainee said something about a plot against an ally, then began slipping into sepsis. He was probably going to die.

The team cabled the morsel of intelligence to C.I.A. headquarters, where it was received with delight by Director George Tenet. "I want to congratulate our officers on the ground," he told a gathering of agents at Langley. When someone explained that the F.B.I. had obtained the information, Tenet blew up and demanded that the C.I.A. get there immediately, say those who were later told of the meeting. Tenet’s instructions were clear: Zubaydah was to be kept alive at all costs. (Through his publisher, George Tenet declined to be interviewed.)

Zubaydah was stabilized at the nearest hospital, and the F.B.I. continued its questioning using its typical rapport-building techniques. An agent showed him photographs of suspected al-Qaeda members until Zubaydah finally spoke up, blurting out that "Moktar," or Khalid Shaikh Mohammed, had planned 9/11. He then proceeded to lay out the details of the plot. America learned the truth of how 9/11 was organized because a detainee had come to trust his captors after they treated him humanely.

Al-Qaeda operative Khalid Shaikh Mohammed shortly after his capture, 2003. Corbis.

It was an extraordinary success story. But it was one that would evaporate with the arrival of the C.I.A’s interrogation team. At the direction of an accompanying psychologist, the team planned to conduct a psychic demolition in which they’d get Zubaydah to reveal everything by severing his sense of personality and scaring him almost to death.

This is the approach President Bush appeared to have in mind when, in a lengthy public address last year, he cited the “tough” but successful interrogation of Zubaydah to defend the C.I.A.’s secret prisons, America’s use of coercive interrogation tactics, and the abolishment of habeas corpus for detainees. He said that Zubaydah had been questioned using an “alternative set” of tactics formulated by the C.I.A. This program, he said, was fully monitored by the C.I.A.’s inspector general and required extensive training for interrogators before they were allowed to question captured terrorists.