A chronology by the Senate Select Committee on Intelligence gives background on the interrogation memos.
March 28, 2002 Abu Zubaida is captured in Pakistan.
May 2002 "According to CIA records, because the CIA believed that Abu Zubaida was withholding imminent threat information during the initial interrogation sessions, attorneys from the CIA's Office of General Counsel met with the Attorney General, National Security Adviser, the Deputy National Security Adviser, the legal adviser to the National Security Council, and Counsel to the President to discuss the possible use of alternative interrogation methods that differed from the traditional methods used by the U.S. military and intelligence community. At this meeting, the CIA proposed particular alternative interrogation methods, including waterboarding."
July 13, 2002 "Attorneys from the CIA Office of General Counsel meet with the legal adviser to the National Security Council, a deputy assistant attorney general from the Office of Legal Counsel, the head of Criminal Division of the Department of Justice, the chief of staff to the Director of the FBI, and the Counsel to the President to provide an overview of the proposed interrogation plan for Abu Zubaida."
July 17, 2002 "Director of Central Intelligence (DCI) met with the National Security Adviser, who advised that the CIA could proceed with its proposed interrogation of Abu Zubaida. This advice, which authorized CIA to proceed as a policy matter, was subject to a determination of legality by OLC."
July 24, 2002 "OLC orally advised the CIA that the Attorney General had concluded that certain proposed interrogation techniques were lawful and, on July 26, that the use of waterboarding was lawful."
Aug. 1, 2002 "OLC issued three documents analyzing U.S. obligations with respect to the treatment of detainees. Two of these three documents were unclassified: an unclassified opinion interpreting the federal criminal prohibition on torture, and a letter concerning U.S. obligations under the Convention Against Torture."
SOURCE: Senate Select Committee on Intelligence