Major McElwain declined to say how much the consolidation cost. Over time, he said, the move would most likely mean a reduction in the troops of the 1,500 mostly National Guard members, who are mainly on nine-month missions during the detention operation, which is estimated to cost an estimated $ 13 million per prisoner per year.

Mr. Mohammed and the other high-quality inmates were held in classified Camp 7 after they were transferred to Guantánamo in September 2006. They had spent three to four years in the George W. Bush administration’s secret overseas prison network known as Black Places, where the CIA subjected prisoners to sleep deprivation, forced nudity, waterboarding, and other physical and mental abuse.

By separating the prisoners under the supervision of a special guard called Task Force Platinum, the secret services were able to closely monitor and control their communications and prevent them from revealing what had happened to them. Criminal defense lawyers who were eventually granted access to the men were tied to security clearances to keep their conversations secret, including on court files accusing government agents of state sponsored torture.

Camp 7 has long been one of the most secret sites in Guantánamo. The Pentagon refused to disclose its costs, which contractor built it and when. Reporters were not allowed to see it, lawyers were required to obtain a court order to visit, and its location was deemed classified, despite sources pointing to it on a base satellite map.

In the short term, said Major McElwain, Camp 7 will be “renovated, closed and locked”.

“A plan for its final disposition has yet to be established,” he said.

The former CIA prisoners were largely kept in isolation in Camp 7 in their early years. Each was allowed to talk to only one other prisoner about a tarpaulin during leisure time, in conversations recorded for intelligence purposes.

Her lawyers described the conditions as numbing until the last few years, when commanders allowed prisoners to eat and pray together under strict surveillance. They also had a cell where they could prepare food to pass the time.