WASHINGTON: The first detailed picture of how so-called high value detainees spent their days inside secret Central Intelligence Agency-run prisons overseas has emerged in dozens of previously classified documents released this week.

The "black sites" were run with the singular goal of extracting potentially valuable information from some of the most high-profile terror suspects in US custody, and there was a clear theory about how that should be done.

"The effectiveness of the program depends on persuading the detainee, early in the application of these techniques, that he's dependent on the interrogators and that he lacks control over his situation," wrote Steven Bradbury, then a senior attorney at the Office of Legal Counsel, an office that gives the president legal advice.

Interrogators, some from private security firms, others agents from the CIA itself, had authorization to slap detainees across the face, force them into uncomfortable stress positions, and keep them awake for 11 consecutive days. If that did not work, they could strap a collar and leash around a detainee's neck, using the leash to repeatedly slam the suspect into a wall.

They could force a suspect into a dark box and leave him there for 18 hours, and if the pressure needed to be increased, insects could be placed inside. If all else had failed, there was waterboarding: interrogators could strap a detainee to a bench with his feet higher than his head, place a cloth firmly over his mouth and nose, and pour water onto his face.