From the Summary: "In building a case for invading Iraq and ousting Saddam Hussein from power, the Administration asserted that the regime of Saddam Hussein had a working relationship with the Al Qaeda organization. The Administration stated that the relationship dated to the early 1990s, and was based on a common interest in confronting the United States. The Administration assertions were derived from U.S. intelligence showing a pattern of contacts with Al Qaeda when its founder, Osama bin Laden, was based in Sudan in the early to mid-1990s and continuing after he relocated to Afghanistan in 1996. […] Another pillar of the Administration argument rested on reports of contacts between Baghdad and an Islamist Al Qaeda affiliate group, called Ansar al-Islam, based in northern Iraq in the late 1990s. Although the connections between Ansar al-Islam and Saddam Hussein's regime were subject to debate, the organization apparently did evolve into what is now known as Al Qaeda in Iraq (AQ-I). AQ-I is a key component of the Sunni Arab-led insurgency that has frustrated U.S. efforts to stabilize Iraq, but there is debate about how large and significant a component of overall violence is carried out by AQ-I. At the same time, U.S. commanders are increasingly focusing combat operations on AQ-I. The U.S. military also has sought, with some success, to exploit differences between AQ-I and Iraqi Sunni political, tribal, and insurgent leaders. There are some indications that AQ-I is attempting to conduct activities outside Iraq in a process that some describe as 'spillover' from Iraq into the broader Middle East."
CRS Report for Congress, RL32217