Guantanamo has 242 remaining prisoners and it could take months to repatriate some and arrange alternative detention facilities on the US mainland for others. One diplomat said: "Obama will start things off pretty fast. We're expecting a very early announcement. There will be a roadmap to closure and there will be some proper process of law. But it won't shut down immediately. We recognise that there are real security threats with some of those left."
A study of the remaining detainees conducted by the Weekly Standard magazine found that of the 242 prisoners, 174 either ran or attended terrorist training camps, 146 have either operated or stayed in an al-Qaeda or Taliban guest houses, 116 have links to jihadist recruiting networks and 112 fought in Afghanistan or elsewhere.
Khalid Sheikh Mohammed is charged with 2,973 counts of murder, one for each person killed on September 11, is probably the most hated prisoner in US custody. The 9/11 Commission labelled him the "principal architect of the 9/11 attacks". Without him there might well have been no 9/11 and no war on terrorism.
Born in Kuwait to Pakistani parents, he moved to America as a teenager and earned a degree in mechanical engineering at a university in North Carolina.
After fighting the Russians in Afghanistan, he funded his nephew Ramzi Yousef's attempt to blow up the World Trade Center in 1993. He also planned the abortive Operation Bojinka, a plot to explode a dozen airliners over the Pacific.
Captured in Pakistan in 2003 and sent to Guantanamo in 2006, Khalid Sheikh Mohammed also confessed to personally beheading the American journalist Daniel Pearl, according to the CIA.
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