While most people associate Sept. 11 with Osama bin Laden, the real mastermind behind the attacks was a man named Khalid Sheikh Mohammed. He is the subject of a new book by Terry McDermott and Josh Meyer called, "The Hunt for KSM: Inside the Pursuit and Takedown of the Real 9/11 Mastermind, Khalid Sheikh Mohammed."
The book traces the activities of Khalid Sheikh Mohammed, or KSM, as he orchestrated dozens of terrorist plots throughout the world, such as the 1993 plot on the World Trade Center. But unlike Osama bin-Laden, Meyer sees KSM as a more complex figure.
"He is a fascinating guy ... a lot of these guys, including bin Laden, are cardboard cutouts. But KSM was always very different ... He sees himself essentially as George Washington leading an insurgent army against an oppressive force."
The book also follows the F.B.I. agent who got an early beat on KSM, Frank Pellegrino. Pellegrino and his partner, Matt Besheer, tracked him from 1994-2001. "Frank was one of the young agents ... a lot of the other FBI agents didn't want to do the traveling overseas, its a real grind, its a career killer," Meyer says.
Pellegrino focused on KSM exclusively, building a case against him through dogged detective work.
"Back then you couldn't 'take someone off the battlefield,' as they say now. You had to gather evidence, you had to get fingerprints, you had to get photo ids," Meyer explains.
"They [Pellegrino and his partner Matt Besheer] were crawling through the jungles of the Philippines and crawling through the really seedy parts of Manilla, talking to bar girls who new KSM ... and literally got the evidence that they needed to build a criminal case and got a grand jury to indict him."
But after pursuing KSM to Qatar in 1996, Pellegrino was thwarted - due in part to the lack of cooperation from the Qatar government. "They came within hours, maybe minutes of catching him in Qatar."
KSM fled to Pakistan, but with little help from the Pakistani government, the case went cold.
Would the Sept. 11 attacks have occurred if KSM had been caught in the '90s?
"The answer is absolutely not. This was his baby, his brainchild. He brought it to bin Laden," Meyer said.
But even after the attacks on Sept. 11, senior government and agency officials did not suspect KSM. According to Meyer, too much energy and focus was placed on pursuing Al-Qaeda.
"I think that the U.S. government, the F.B.I., the C.I.A. and others were so fixated on Osama bin Laden in the mid and certainly the late 1990s, they didn't see KSM."
Despite eventually being apprehended in Pakistan in 2003, Pellegrino was not allowed to interrogate KSM because both he and Besheer had been completely marginalized by the Bush administration's decision to hand over interrogation to the C.I.A.
From 2003 to 2007, KSM was taken to black sites for interrogation. He was water-boarded 183 times and tortured in numerous other ways. But Meyer explains that KSM quickly adapted to the hardship, "It became a game to him ... he quickly determined the limits of what they were able to do ... he would almost taunt his captors."
And Meyer isn't so sure that KSM lost the battle, "I think history will have to be the judge of that ... I would say the pendulum is pretty far on the side where he was holding operational information."
Finally in 2007, Pellegrino was allowed to interrogate KSM. It was a dramatic face off. Pellegrino got information from KSM that will form the backbone of the government's prosecution.
KSM now faces trial by a military tribunal, but his legacy continues to live on in the recruitment work he did around the globe. He consciously sought and nurtured young people with European and American roots, able to pop up at a moment's notice to carry out an attack.
"People tend to look at KSM as a historical figure ... [but] he created sort of a layer of proteges and lieutenants ... I know that are many authorities that are terrified that these guys could pop up any time," he said.
Correction:An earlier version of this article quoted Josh Meyer out of context and incorrectly stated that Khalid Sheikh Mohammed's capture could not have prevented Sept. 11. In fact, Meyer said Sept. 11 would not have happened without KSM.