GUANTANAMO BAY NAVY BASE, Cuba -- 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.

“The government wants to kill Mr. Mohammed. They want to extinguish the last eyewitness to his torture so that he can never speak about it,” Mohammed’s defense attorney, David Nevin, told reporters in May after a 13-hour arraignment.

Just how much the world can know — and how much their lawyers can learn — about the years Mohammed and the other four men spent in the CIA prison network will be front and center this week at pre-trial hearings. The government argues that whatever the men say about their time in the so-called “black sites” is Top Secret, classified at the highest levels.

The hearings start Monday and run all week, and will cover a range of issues from whether the prison camps can compel the men to attend their own trials to whether they can wear paramilitary attire to court. They were scheduled for August but delayed by Tropical Storm Isaac.

None of the men are particularly sympathetic characters.

Soon after Mohammed got to Guantánamo from the prison network where, the CIA’s own declassified documents disclose, he was waterboarded 183 times, the U.S.-educated, Pakistani-born man bragged to a military panel that he orchestrated the 9/11 attacks from “A to Z.”

His four accused accomplices allegedly trained, funded and arranged travel for the 19 hijackers that killed nearly 3,000 people at the World Trade Center, Pentagon and in a Pennsylvania field in the worst terror attack on U.S. soil. At their May arraignment, they refused to answer the judge’s questions.

Now this week, Army Col. James Pohl, the judge, will hear arguments from lawyers on how much the world can hear — and how much their own defense lawyers can discuss with the accused — of what happened to them during their years in CIA custody.

The chief war crimes prosecutor, Army Brig. Gen. Mark Martins, says the court is as transparent as the agencies that control the classifications allow. Meaning, if the CIA has declared something a secret, the government’s Pentagon prosecution team is bound to keep that secret.

Information is classified “to safeguard genuine sources and methods of intelligence gathering that can protect against future attack,” the general told an audience in London last month as part of a periodic speaking meant to quell criticism of the war court.

The government can’t close proceedings, he said, to shield the United States from embarrassment or to cover up that a law was broken.

Defense lawyers oppose the idea that anything the accused say is “presumptively classified.” They say the prison camps rules imposed on their work means that, as Nevin put it, attorney and captive are forbidden to discuss between themselves anything from what Mohammed says the CIA did to him to his “historical perspective on jihad.” Nevin called the war court system “a rigged game.”