The Justice Department made public on Thursday detailed memos describing harsh interrogation techniques used by the Central Intelligence Agency, as President Obama said that C.I.A. operatives who carried out the techniques would not be prosecuted.
One technique authorized for use by the C.I.A. beginning in August 2002 was the use of “insects placed in a confinement box,” presumably to induce fear on the part of a terror suspect.
The interrogation methods were among the Bush administration’s most closely guarded secrets, and what was released on Thursday afternoon marked the most comprehensive public accounting to date of a program that some senior Obama administration officials have said included illegal torture.
One memo showed that a top Justice Department lawyer issued a legal opinion in 2005 saying that C.I.A. officers were allowed to use a combination of interrogation methods to produce a more effective result.
“Interrogators may combine water dousing with other techniques, such as stress positions, wall standing, the insult slap, or the abdominal slap,” wrote the official, Stephen G. Bradbury.
But Mr. Obama used a written statement to reiterate his opposition to a extensive investigation of the program, saying it was “time for reflection, not retribution.” He added:
“In releasing these memos, it is our intention to assure those who carrying out their duties relying in good faith upon the legal advice from the Department of Justice that they will not be subject to prosecution.”
An early review suggested that the administration had declassified the vast bulk of the memos’ contents, a defeat for C.I.A. officials who had argued that such a step could be harmful to national security. The documents included Justice Department memos from 2002 and 2005 authorizing the C.I.A. to employ a number of aggressive techniques — including sleep deprivation, exposure to extreme temperatures and “waterboarding,” the near-drowning technique.