US Attorney General Eric Holder said Friday that Sheikh Mohammed, 44, will face a death penalty trial in federal court in New York for allegedly masterminding the 2001 attacks that claimed nearly 3,000 lives.
In addition to felling the twin towers, KSM claims to have personally beheaded US journalist Daniel Pearl in 2002 with his "blessed right hand" and to have helped in the 1993 World Trade Center bombing that killed six people.
Among several plots admitted to interrogators that failed to materialize were assassinations of the late pope John Paul II and former US presidents Bill Clinton and Jimmy Carter.
Sheikh Mohammed was born on April 24, 1965 to a Pakistani family living in the conservative Gulf sheikhdom of Kuwait but his roots lie in Baluchistan, a restive Pakistani region bordering Afghanistan.
He claims to have joined the Muslim Brotherhood, a Sunni Muslim militant group, when he was 16, beginning a life-long infatuation with violent jihad.
In 1983, Sheikh Mohammed moved to the United States for his studies and graduated from North Carolina Agricultural and Technical State University with a degree in mechanical engineering three years later.
The following year he travelled to Afghanistan and fought for the Islamic mujahideen against the Soviet invasion but it was not until a botched 1995 plot to blow up US airliners over the Pacific, known as Operation Bojinka, that he achieved notoriety.
Safely out of reach in Qatar by the time the Philippine authorities unraveled the plot, KSM was thought to have participated in the planning of an attack for the first time, having only contributed money to his nephew Ramzi Yousef's 1993 car-bombing at the World Trade Center.
Although he and Bin Laden fought together in Afghanistan in the late 1980s, it wasn't until 10 years later that they forged a close relationship and KSM allegedly began plotting what would later become the September 11 attacks.
Most of what we know about Sheikh Mohammed has come from interrogation transcripts released from the Pentagon and there are bound to be questions at his trial over the harsh procedures used to obtain that information.
He is known to have been "waterboarded" or subjected to simulated drowning 183 times during his years in US custody.
In the reported confessions released in March last year, Sheikh Mohammed was quoted as claiming to be "military operational commander" for all Al-Qaeda foreign operations.
"I'm not making myself a hero, when I said I was responsible for this or that," he was quoted as saying in the transcript.
"I'm looking to be a martyr for long time," he told a hearing at Guantanamo in June last year, the first time he had been seen in public since his 2003 arrest in Rawalpindi, Pakistan.
He was handed over almost immediately to US agents who held him in secret prisons for over three years before sending him to Guantanamo in September 2006.
Photos released by the US military at the time showed a wild-eyed, disheveled man in a white T-shirt, but more recent pictures have shown him with a long black and gray beard and a white turban.
The official US report into the September 11 attacks said that "no one exemplifies the model of the terrorist entrepreneur more clearly than Khalid Sheikh Mohammed."
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Image: AFP/HO/File.
In addition to felling the twin towers, KSM claims to have personally beheaded US journalist Daniel Pearl in 2002 with his "blessed right hand" and to have helped in the 1993 World Trade Center bombing that killed six people.
Among several plots admitted to interrogators that failed to materialize were assassinations of the late pope John Paul II and former US presidents Bill Clinton and Jimmy Carter.
Sheikh Mohammed was born on April 24, 1965 to a Pakistani family living in the conservative Gulf sheikhdom of Kuwait but his roots lie in Baluchistan, a restive Pakistani region bordering Afghanistan.
He claims to have joined the Muslim Brotherhood, a Sunni Muslim militant group, when he was 16, beginning a life-long infatuation with violent jihad.
In 1983, Sheikh Mohammed moved to the United States for his studies and graduated from North Carolina Agricultural and Technical State University with a degree in mechanical engineering three years later.
The following year he travelled to Afghanistan and fought for the Islamic mujahideen against the Soviet invasion but it was not until a botched 1995 plot to blow up US airliners over the Pacific, known as Operation Bojinka, that he achieved notoriety.
Safely out of reach in Qatar by the time the Philippine authorities unraveled the plot, KSM was thought to have participated in the planning of an attack for the first time, having only contributed money to his nephew Ramzi Yousef's 1993 car-bombing at the World Trade Center.
Although he and Bin Laden fought together in Afghanistan in the late 1980s, it wasn't until 10 years later that they forged a close relationship and KSM allegedly began plotting what would later become the September 11 attacks.
Most of what we know about Sheikh Mohammed has come from interrogation transcripts released from the Pentagon and there are bound to be questions at his trial over the harsh procedures used to obtain that information.
He is known to have been "waterboarded" or subjected to simulated drowning 183 times during his years in US custody.
In the reported confessions released in March last year, Sheikh Mohammed was quoted as claiming to be "military operational commander" for all Al-Qaeda foreign operations.
"I'm not making myself a hero, when I said I was responsible for this or that," he was quoted as saying in the transcript.
"I'm looking to be a martyr for long time," he told a hearing at Guantanamo in June last year, the first time he had been seen in public since his 2003 arrest in Rawalpindi, Pakistan.
He was handed over almost immediately to US agents who held him in secret prisons for over three years before sending him to Guantanamo in September 2006.
Photos released by the US military at the time showed a wild-eyed, disheveled man in a white T-shirt, but more recent pictures have shown him with a long black and gray beard and a white turban.
The official US report into the September 11 attacks said that "no one exemplifies the model of the terrorist entrepreneur more clearly than Khalid Sheikh Mohammed."
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Image: AFP/HO/File.