Syria had accumulated much of its information because of Al Qaeda’s ties to the Syrian Muslim Brotherhood, Islamic terrorists who have been at war with the secular Syrian government for more than two decades. Many of the September 11th hijackers had operated out of cells in Aachen and Hamburg, where Al Qaeda was working with the Brotherhood. In the late nineties, Mohammed Atta and other Al Qaeda members, including Mohammed Haydar Zammar, who is believed to have been one of the organization’s top recruiters, worked on occasion at a German firm called Tatex Trading. Tatex was infiltrated by Syrian intelligence in the eighties; one of its shareholders was Mohammed Majed Said, who ran the Syrian intelligence directorate from 1987 to 1994. Zammar is now in Syrian custody.Within weeks of the September 11th attacks, the F.B.I. and the C.I.A, with Syria’s permission, began intelligence-gathering operations in Aleppo, near the Turkish border. Aleppo was the subject of Mohammed Atta’s dissertation on urban planning, and he travelled there twice in the mid-nineties. “At every stage in Atta’s journey is the Muslim Brotherhood,” a former C.I.A. officer who served undercover in Damascus told me. “He went through Spain in touch with the Brotherhood in Hamburg.”