"If you're asking, are there al-Qaeda in Iraq, the answer is yes, there are. It's a fact, yes." Donald Rumsfeld, US Secretary of Defence, August 2002
It was one of the key American justifications for the Iraq war. But the theory that al-Qaeda was present in Saddam-era Iraq, much cited by the Bush adminsitration in the run-up to the invasion, has been undermined by the content of secret US military documents.
The files contain only half a dozen references to the group for the whole of 2004, the year records begin. But under the leadership of Abu Musab al-Zarqawi, a Jordanian who had met Osama bin Laden while fighting the Soviet occupation of Afghanistan, the classified reports show that al-Qaeda established itself as major player in the carnage as the conflict wore on.
The infrequency of al-Qaeda-related files early in the war suggest that US officials were wrong when they accused Iraq of harbouring the group's fighters in the years prior to the invasion. Instead, the narrative that emerges from the classified reports indicates that the US presence itself was what attracted them to the country.
Experts have always doubted the existence of a link between the secular Baathist government of Saddam Hussein and al-Qaeda.
Speaking at the British inquiry into the Iraq War in 2005, Eliza Manningham-Buller, the UK's spy chief at the time of the invasion, said that even US intelligence officials doubted a connection between Iraq and the group.