GUANTANAMO BAY NAVY BASE, Cuba (MCT) — The five men accused of plotting the terror attacks of Sept. 11, 2001, were in the custody of the CIA for up to four years before they were brought here for detention and trial. But exactly where the CIA held them and what was done to them there is a state secret at the military court in which they are charged with war crimes.

In 2008, Gen. Michael V. Hayden, then head of the CIA, told Congress that the alleged mastermind, Khalid Sheik Mohammed, was waterboarded. Hayden didn’t say where or how or whether anything else was done to Mohammed in an attempt to get him to give up al-Qaida’s secrets.