The CIA tortured al-Qaeda suspects because it wanted evidence that Saddam Hussein was linked to 9/11 in order to justify the invasion of Iraq in 2003. The agency was under intense pressure from the White House and senior figures in the Bush administration to extract confessions confirming co-operation between the Iraqi leader and al-Qaeda, although no significant evidence was ever found.

The CIA has defended its actions by claiming that it was “unknowable” if torture had produced results, although the chairman of the Senate Intelligence Committee, Dianne Feinstein, maintains torture produced nothing of value.

A second line of defence put forward by defenders of the CIA is to say that the agency was swept up in the reaction to 9/11 in the US and needed to find out quickly if there were going to be further attacks.

Telling evidence about the motives of the CIA in instituting its torture programme comes in a report on detainee abuse issued by the Senate Armed Services Committee in 2009. It cited a former US Army psychiatrist, Major Charles Burney, who had been stationed at Guantanamo Bay, as saying interrogators were compelled to give priority to one line of questioning.

“A large part of the time we were focused on trying to establish a link between al-Qaeda and Iraq,” he said. When interrogators failed to do this “there was more and more pressure to resort to measures that might produce more immediate results”.

CIA torture report: Who knew what? Show all 6 1 /6 CIA torture report: Who knew what? CIA torture report: Who knew what? GEORGE W BUSH FORMER US PRESIDENT President Bush has stated in his autobiography that he discussed the programme, including the use of enhanced techniques, with then CIA director George Tenet in 2002, prior to application of the techniques on Abu Zubaydah, and personally approved them. A memoir by the former Acting CIA General Counsel John Rizzo disputes this. AFP/Getty CIA torture report: Who knew what? JOHN BRENNAN FORMER DEPUTY DIRECTOR AND NOW DIRECTOR, CIA Among those who were sent an update on 26 July 2002, in which CIA officers were said to be involved in “sound disorientation techniques,” “sense of time deprivation,” limited light, cold temperatures”, and sleep deprivation. The plan was circulated to senior CIA officers. Getty CIA torture report: Who knew what? CONDOLEEZZA RICE FORMER NATIONAL SECURITY ADVISER On 31 July, 2002, she said that, in balancing the application of the CIA’s interrogation techniques against the possible loss of American lives, she would not object to the CIA’s enhanced interrogation techniques if the Attorney General determined them to be legal. Getty CIA torture report: Who knew what? GEORGE J TENET FORMER DIRECTOR OF CENTRAL INTELLIGENCE, CIA In late January 2003, in response to the death of CIA detainee Gul Rahman and the use of a gun and a drill in the CIA interrogations, DCI Tenet signed the first formal interrogation and confinement guidelines for the programme. Getty CIA torture report: Who knew what? DONALD RUMSFELD FORMER SECRETARY OF DEFENCE Donald Rumsfeld was made aware of the CIA interrogation programme prior to recertification of the covert action for the first time in a 25-minute briefing on 16 September, 2003. It was Condoleezza Rice who ordered his briefing. Getty CIA torture report: Who knew what? COLIN POWELL FORMER SECRETARY OF STATE A CIA email dated 31 July, 2003 states: “The [White House] is extremely concerned [Secretary of State] Powell would blow his stack if he were to be briefed on what’s been going on.” He was formally briefed for the first time on 16 September that year. AFP/Getty

This explanation is confirmed by an unnamed former senior US intelligence officer familiar with the interrogations, who told the McClatchy news agency that there were two reasons “why these interrogations were so persistent and why extreme methods were used”. One was fear there might be a second attack by al-Qaeda. He added that “for most of 2002 and into 2003, [Vice-President Dick] Cheney and [Defence Secretary Donald] Rumsfeld were also demanding proof of the links between al-Qaeda and Iraq.”

On being told repeatedly by the CIA that there was no reliable intelligence about such links, Mr Cheney and Mr Rumsfeld insisted harsher methods be used. The officer said: “There was constant pressure on the intelligence agencies and the interrogators to do whatever it took to get that information out of the detainees, and when people kept coming up empty, they were told by Cheney’s and Rumsfeld’s people to push harder.”

The most severe torture sessions took place in the run-up to the war in 2003, suggesting that rather than preventing further action by al-Qaeda, the US administration was intent on justifying the invasion of Iraq. One prisoner, Abu Zubaydah, who was wrongly thought to be an al-Qaeda leader by his interrogators, was waterboarded 83 times in August 2002, and Khalid Sheikh Mohammed 183 times in March 2003. The first questions asked of the latter after he was captured in Rawalpindi, Pakistan, were all about Iraq and not about forthcoming al-Qaeda attacks, according to The Eleventh Day: The Full Story of 9/11 by Anthony Summers and Robbyn Swan.

Khalid Sheikh Mohammed was waterboarded 183 times and confessed to planning 9/11 (AP)

Senior members of the Bush administration went on pressing for the use of brutal methods amounting to torture against Iraqi prisoners taken after the invasion, trying to make them corroborate an al-Qaeda connection. Summers and Swan cite the CIA’s Charles Duelfer, in charge of interrogating Iraqi officials, as saying that senior officials in Washington, although not in the CIA, had suggested waterboarding an Iraqi official to get the evidence they wanted. Two other US intelligence officers said the proposal came from Mr Cheney’s office.

The CIA was in a poor position to resist pressure from the administration because of its failure to predict or prevent 9/11. But for security agencies, it was a moment of opportunity to gain bigger budgets, more personnel and wider authority in order to punish the perpetrators and prevent a second attack.