Even as members of Al Qaeda watched in exultation while the Twin Towers fell and the Pentagon burned on September 11, 2001, they realized that the pendulum of catastrophe was swinging in their direction. Osama bin Laden later boasted that he was the only one in the group’s upper hierarchy who had anticipated the magnitude of the wound that Al Qaeda inflicted on America, but he also admitted that he was surprised by the towers’ collapse. His goal, for at least five years, had been to goad America into invading Afghanistan, an ambition that had caused him to continually raise the stakes—the simultaneous bombings of the United States Embassies in Kenya and Tanzania, in August, 1998, followed by the attack on an American warship in the harbor of Aden, Yemen, in October, 2000. Neither of those actions had led the United States to send troops to Afghanistan. After the attacks on New York and Washington, however, it was clear that there would be an overwhelming response. Al Qaeda members began sending their families home and preparing for war.

Two months later, the Taliban government in Afghanistan, which had given sanctuary to bin Laden, was routed, and the Al Qaeda fighters in Tora Bora were pummelled. Although bin Laden and his chief lieutenants escaped death or capture, nearly eighty per cent of Al Qaeda’s members in Afghanistan were killed. Worse, Al Qaeda’s cause was repudiated throughout the world, even in Muslim countries, where the indiscriminate murder of civilians and the use of suicide operatives were denounced as being contrary to Islam. The remnants of the organization scattered and were on the run. Al Qaeda was essentially dead.

From hiding places in Iran, Yemen, Iraq, and the tribal areas of western Pakistan, Al Qaeda’s survivors lamented their failed strategy. Abu al-Walid al-Masri, a senior leader of Al Qaeda’s inner council, later wrote that Al Qaeda’s experience in Afghanistan was “a tragic example of an Islamic movement managed in an alarmingly meaningless way.” He went on, “Everyone knew that their leader was leading them to the abyss and even leading the entire country to utter destruction, but they continued to carry out his orders faithfully and with bitterness.”

In June, 2002, bin Laden’s son Hamzah posted a message on an Al Qaeda Web site: “Oh, Father! Where is the escape and when will we have a home? Oh, Father! I see spheres of danger everywhere I look. . . . Tell me, Father, something useful about what I see.”

“Oh, son!” bin Laden replied. “Suffice to say that I am full of grief and sighs. . . . I can only see a very steep path ahead. A decade has gone by in vagrancy and travel, and here we are in our tragedy. Security has gone, but danger remains.”

In the view of Abu Musab al-Suri, a Syrian who had been a member of Al Qaeda’s inner council, and who is a theorist of jihad, the greatest loss was not the destruction of the terrorist organization but the downfall of the Taliban, which meant that Al Qaeda no longer had a place to train, organize, and recruit. The expulsion from Afghanistan, Suri later wrote, was followed by “three meager years which we spent as fugitives,” dodging the international dragnet by “moving between safe houses and hideouts.” In 2002, he fled to eastern Iran, where bin Laden’s son Saad and Al Qaeda’s security chief, Saif al-Adl, had also taken refuge. There was a five-million-dollar bounty on his head. In this moment of exile and defeat, he began to conceive the future of jihad.

Suri was born into a middle-class family in Aleppo, Syria, in 1958, the year of bin Laden’s birth. Red-haired and sturdily built, he has a black belt in judo; his real name is Mustafa Setmariam Nasar. He became involved in politics at the University of Aleppo, where he studied engineering. Later, he moved to Jordan, where he joined the Muslim Brotherhood, an Islamist group that opposed Syria’s dictator, Hafez al-Assad. In 1982, Assad decided that the Brotherhood posed a threat to his authority, and his troops slaughtered as many as thirty thousand people in the city of Hama, one of the group’s strongholds. The ruthlessness of Assad’s response shocked Suri. He renounced the Brotherhood, which he held responsible for provoking the destruction of Hama, and took refuge in Europe for several years. In 1985, he moved to Spain, where he married and became a Spanish citizen; two years later, he found his way to Afghanistan, where he met Osama bin Laden.

The two men have had a contentious relationship. Although Suri became a member of Al Qaeda’s inner council, he grew disillusioned by the fecklessness and the disorganization that characterized Al Qaeda’s training camps in Afghanistan. “People come to us with empty heads and leave us with empty heads,” he wrote. “They have done nothing for Islam. This is because they have not received any ideological or doctrinal training.”

In 1992, he moved back to Spain, where he helped to establish a terrorist cell that played a part in the planning of September 11th. Two years later, Suri moved to England. He soon became a fixture in the Islamist press in London, writing articles for the magazine Al Ansar, which promoted the insurgency in Algeria that resulted in more than a hundred thousand deaths. The magazine’s editor was Abu Qatada, a Palestinian cleric who has been characterized as Al Qaeda’s spiritual guide in Europe. Al Ansar was, in many ways, the first jihadi think tank; Suri and other strategists suggested tactics for undermining the despotic regimes in the Arab world, and they promoted attacks on the West even as American and European intelligence agencies were largely unaware of the threat that the Islamist movement posed.

Jamal Khashoggi, a Saudi journalist who is currently the press aide to the Saudi Ambassador in Washington, Prince Turki al-Faisal, met Qatada and Suri in the early nineties. They struck him as far more radical than Osama bin Laden; at the time, Al Qaeda was primarily an anti-Communist organization. “Osama was in the moderate camp,” Khashoggi recalled recently. He coined the phrase “Salafi jihadis” to describe men, such as Abu Qatada and Suri, who had been influenced by Salafism, the puritanical, fundamentalist strain of Islam. “Osama was flirting with these ideas,” Khashoggi said. “He was not the one who originated the radical thinking that came to characterize Al Qaeda. He joined these men, rather than the other way around. His organization became the vehicle for their thinking.”

Suri later wrote about bin Laden’s conversion to his ideas, which took place after bin Laden returned to Afghanistan, in 1996. Salafi jihadis spoke with him about a situation that angered him deeply: the presence of American troops on the holy soil of the Arabian Peninsula. Corrupt Islamic scholars had lent their authority to the Saudi royal family, the jihadis argued, and the royal family, in turn, had given legitimacy to the American incursion. There were two possible solutions: either attack the royal family—which would likely anger the Saudi people—or strike at the American presence. “This would force the Saudi family to defend it, thereby losing its own legitimacy in the eyes of Muslims,” Suri writes. “Bin Laden chose the second option.”