In a squat, red-brick building next to Khartoum's presidential palace, the agents who serve the Mukhabarat, Sudan's intelligence division, keep their secrets in pale manila files. 
"Those guys know what they're doing," says a retired longtime C.I.A. Africa specialist. "They tend to be thorough. Their stuff is pretty reliable."
And sometimes very important. Sudan's Mukhabarat spent the early to mid-1990s amassing copious intelligence on Osama bin Laden and his leading cohorts at the heart of the al-Qaeda terrorist network—when they were still little known, and their activities were relatively limited. Some of the files at Mukhabarat headquarters identify individuals who played central roles in the suicide bombings of the U.S. Embassies in Tanzania and Kenya in August 1998; others chart the backgrounds and movements of al-Qaeda operatives who are said to be linked directly to the atrocities of September 11. In the wake of those attacks, President Bush and the F.B.I. issued a list of the world's 22 most wanted terrorists. Sudan has kept files on many of them for years.
From the autumn of 1996 until just weeks before the 2001 attacks, the Sudanese government made numerous efforts to share this information with the United States—all of which were rebuffed. On several occasions, senior agents at the F.B.I. wished to accept these offers, but were apparently overruled by President Clinton's secretary of state, Madeleine Albright, and her assistant secretary for Africa, Susan Rice, both of whom would not comment for this story after repeated requests for interviews. Vanity Fair has obtained letters and secret memorandums that document these approaches. They were made directly to the State Department and the F.B.I., and also via a series of well-connected U.S. citizens who tried to warn America that the Sudanese offers were serious and significant.
By definition, September 11 was an intelligence failure. As the C.I.A. man puts it, "We didn't know it was going to happen." Some of the reasons for that failure were structural, systemic: the shortage of Arabic-speaking agents, the inability of C.I.A. officers to go underground in Afghanistan.
This one was more specific. Had U.S. agencies examined the Mukhabarat files when they first had the chance in 1996, the prospects of preventing al-Qaeda's subsequent attacks would have been much greater. Tim Carney, the last U.S. ambassador to Sudan, whose posting ended in 1997, says: "The fact is, they were opening the doors, and we weren't taking them up on it. The U.S. failed to reciprocate Sudan's willingness to engage us on serious questions of terrorism. We can speculate that this failure had serious implications—at the least for what happened at the U.S. Embassies in 1998. In any case, the U.S. lost access to a mine of material on bin Laden and his organization."
How could this have happened? The simple answer is that the Clinton administration had accused Sudan of sponsoring terrorism, and refused to believe that anything it did to prove its bona fides could be genuine. At the same time, perceptions in Washington were influenced by C.I.A. reports that were wildly inaccurate, some the result of deliberate disinformation. The problem, Carney says, was "inadequate vetting and analysis by the C.I.A. of its own product." That, in turn, was being conditioned by the Clinton administration's hostility to Sudan's Islamic regime: "Despite dissent from the State Department's own Bureau of Intelligence and Research, U.S. intelligence failed because it became politicized."
Osama bin Laden, his four wives, his children, and numerous "Afghan Arab" followers who had helped drive the Soviets from Afghanistan went to Sudan from Saudi Arabia early in 1991. They chose Sudan for two main reasons. First, the restless, radicalized veterans of the Afghan war were unwelcome in most Arab countries, but Sudan left its doors open. Second, bin Laden liked Sudan's politics. The Islamic radicalism of the government's then ideological leader, the philosopher Hassan al-Turabi, who had come to power in a coup d'état in 1989, was at its bracing zenith. The Sudanese, in turn, welcomed bin Laden as an investor. His family had built most of Saudi Arabia's infrastructure, and they saw his wealth and experience as an engineer as valuable resources in developing Sudan.
Al-Qaeda, with its secretive structure and oath of allegiance to bin Laden, had been founded two years earlier. In Sudan, however, much of bin Laden's energy went into business: a contract, funded by the Saudis, to build the airport at Port Sudan; agricultural projects; and al-Hijra, a joint venture with the Sudan government to build a 185-mile road northward from Khartoum. Abu Ibrahim, the Iraqi engineer who became al-Hijra's C.E.O., says bin Laden took a strong interest in the project's technical details. In bin Laden's large house in an affluent part of Khartoum, they spent hours together, discussing which diggers, graders, and other items the firm ought to buy. On his visits to the site, Ibrahim says, bin Laden showed "he knew how to drive every piece of machinery." Ibrahim had known bin Laden during the Afghan war. "When we were in Afghanistan, everything was jihad, jihad, jihad," he says. "Here in Sudan we saw his many other aspects—construction, family life. He was settling down."
However, bin Laden also found time to begin a fierce propaganda campaign against the Saudi government, furious that it had allowed the U.S. military to build bases on Saudi soil. By 1994 that campaign had led to the removal of his Saudi citizenship. He was also fostering contacts with other Muslim extremists—some of whom were very dangerous indeed.
As we sat on gray-green leather sofas in his office, Yahia Hussien Ba-viker, the Mukhabarat's deputy chief since 1998, disclosed a nugget from 1992. In that year, the Mukhabarat learned that bin Laden had played host for a lengthy visit by Ayman al-Zawahiri, the founder of Egyptian Islamic Jihad—a fundamentalist group behind many armed attacks on Egyptian government ministers and officials, including the 1981 assassination of President Anwar el-Sadat.
The Mukhabarat had monitored Egyptian Islamic Jihad for years. "If anyone in the world understands the Egyptian side of this network, it's Sudan," the C.I.A. source says. Events have served to demonstrate the significance of that meeting in 1992: Egyptian Islamic Jihad has effectively merged with al-Qaeda. Al-Zawahiri, now No. 2 on the F.B.I.'s "most wanted" list, serves as bin Laden's doctor and adviser in Afghanistan. Other Egyptians occupy core positions within the al-Qaeda network, many of them known to the Mukhabarat since the 1980s. "These files on the Egyptians could have been of great value to U.S. intelligence," Baviker says. "If we'd had communication with the U.S., we could have been on the same wavelength. We could have exchanged notes."
