http://www.nytimes.com/2009/04/18/world/middleeast/18zubaydah.html?_r=1&hp<snip>
Through the summer of 2002, Abu Zubaydah continued to provide valuable information. Interrogators began to surmise that
he was not a leader, but rather a helpful training camp personnel clerk who would arrange false documents and travel for jihadists, including Qaeda members.
He knew enough to give interrogators “a road map of Al Qaeda operatives,” an agency officer said. He also repeated talk he had heard about possible plots or targets in the United States, though when F.B.I. agents followed up, most of it turned out to be idle discussion or preliminary brainstorming.
...
But senior agency officials, still persuaded, as they had told President George W. Bush and his staff, that he was an important Qaeda leader, insisted that he must know more.
“You get a ton of information, but headquarters says, ‘There must be more,’ ” recalled one intelligence officer who was involved in the case.
As described in the footnote to the memo, the use of repeated waterboarding against Abu Zubaydah was ordered “at the direction of C.I.A. headquarters,” and officials were dispatched from headquarters “to watch the last waterboard session.”