On Sunday, March 31, three days after the raid, the interrogation of Zubaydah began. For the particulars of this episode there is one definitive source, Gerald Posner's "Why America Slept," and according to it, the CIA used two rather unusual methods for the interrogation. First, they administered thiopental sodium, better known under its trademarked name, Sodium Pentothal, through an IV drip, to make Zubaydah more talkative. Since the prisoner had been shot three times during the capture, he was already hooked up to a drip to treat his wounds and it was possible to administer the drug without his knowledge. Second, as a variation on the good cop-bad cop routine, the CIA used two teams of debriefers. One consisted of undisguised Americans who were at least willing to treat Zubaydah's injuries while they interrogated him. The other team consisted of Arab-Americans posing as Saudi security agents, who were known for their brutal interrogation techniques. The thinking was that Zubaydah would be so scared of being turned over to the Saudis, infamous for their public executions in Riyadh's Chop-Chop Square, that he would try to win over the American interrogators by talking to them.

In fact, exactly the opposite happened. "When Zubaydah was confronted with men passing themselves off as Saudi security officers, his reaction was not fear, but instead relief," Posner writes. "The prisoner, who had been reluctant even to confirm his identity to his American captors, suddenly started talking animatedly. He was happy to see them, he said, because he feared the Americans would torture and then kill him. Zubaydah asked his interrogators to call a senior member of the ruling Saudi family. He then provided a private home number and cell phone number from memory. 'He will tell you what to do,' Zubaydah promised them."

The name Zubaydah gave came as a complete surprise to the CIA. It was Prince Ahmed bin Salman bin Abdul Aziz, the owner of so many legendary racehorses and one of the most westernized members of the royal family.

Zubaydah spoke to his faux Saudi interrogators as if they, not he, were the ones in trouble. He said that several years earlier the royal family had made a deal with al-Qaida in which the House of Saud would aid the Taliban so long as al-Qaida kept terrorism out of Saudi Arabia. Zubaydah added that as part of this arrangement, he dealt with Prince Ahmed and two other members of the House of Saud as intermediaries, Prince Sultan bin Faisal bin Turki al-Saud, a nephew of King Fahd's, and Prince Fahd bin Turki bin Saud al-Kabir, a 25-year-old distant relative of the king's. Again, he furnished phone numbers from memory.

According to Posner, the interrogators responded by telling Zubaydah that 9/11 changed everything. The House of Saud certainly would not stand behind him after that. It was then that Zubaydah dropped his real bombshell. "Zubaydah said that 9/11 changed nothing because Ahmed ... knew beforehand that an attack was scheduled for American soil that day," Posner writes. "They just didn't know what it would be, nor did they want to know more than that. The information had been passed to them, said Zubaydah, because bin Laden knew they could not stop it without knowing the specifics, but later they would be hard-pressed to turn on him if he could disclose their foreknowledge."

Two weeks later, Zubaydah was moved to an undisclosed location. When he figured out that the interrogators were really Americans, not Saudis, Posner writes, he tried to strangle himself, and later recanted his entire tale.

Here's another resource.

How's it stack up with Posner?

Abu Zubaydah, his captors discovered, turned out to be mentally ill and nothing like the pivotal figure they supposed him to be. CIA and FBI analysts, poring over a diary he kept for more than a decade, found entries "in the voice of three people: Hani 1, Hani 2, and Hani 3" -- a boy, a young man and a middle-aged alter ego. All three recorded in numbing detail "what people ate, or wore, or trifling things they said." Dan Coleman, then the FBI's top al-Qaeda analyst, told a senior bureau official, "This guy is insane, certifiable, split personality."

Abu Zubaydah also appeared to know nothing about terrorist operations; rather, he was al-Qaeda's go-to guy for minor logistics -- travel for wives and children and the like. That judgment was "echoed at the top of CIA and was, of course, briefed to the President and Vice President," Suskind writes. And yet somehow, in a speech delivered two weeks later, President Bush portrayed Abu Zubaydah as "one of the top operatives plotting and planning death and destruction on the United States." And over the months to come, under White House and Justice Department direction, the CIA would make him its first test subject for harsh interrogation techniques.

...

"I said he was important," Bush reportedly told Tenet at one of their daily meetings. "You're not going to let me lose face on this, are you?" "No sir, Mr. President," Tenet replied. Bush "was fixated on how to get Zubaydah to tell us the truth," Suskind writes, and he asked one briefer, "Do some of these harsh methods really work?" Interrogators did their best to find out, Suskind reports. They strapped Abu Zubaydah to a water-board, which reproduces the agony of drowning. They threatened him with certain death. They withheld medication. They bombarded him with deafening noise and harsh lights, depriving him of sleep. Under that duress, he began to speak of plots of every variety -- against shopping malls, banks, supermarkets, water systems, nuclear plants, apartment buildings, the Brooklyn Bridge, the Statue of Liberty. With each new tale, "thousands of uniformed men and women raced in a panic to each . . . target." And so, Suskind writes, "the United States would torture a mentally disturbed man and then leap, screaming, at every word he uttered."

So, they erased the tapes. What was on those tapes?