Muhammad Idrees Ahmad in In These Times:
Prior to the invasion, the Jordanian militant Abu Mus’ab al Zarqawi was a marginal figure. The war gave him a foothold: He stepped into the security vacuum and launched Al Qaeda in Iraq (AQI). Zarqawi’s project was aided by the ham-fistedness of the occupying authorities. Viceroy Paul Bremer’s disbanding of the Iraqi national army and purging of Baathists from state bureaucracies created a large pool of disaffected Sunnis. With little to lose, many of them put their arms and military training in the service of the insurgency. The alienation was complete when, in its attempt to divide the nationalist uprising, the U.S. empowered sectarian death squads and deployed Shia and Kurdish forces to the restive Sunni stronghold of Fallujah.
After the new Iraqi government launched an assault on the Sunni town of Tal Afar in September 2005, Zarqawi declared war on Iraq’s Shia Muslim population, and AQI became a home for Sunnis fearful of Shia domination. But the majority of Iraq’s Sunnis remained wary of its motives: The scope of AQI’s ambitions—establishing a pan-Islamic Sunni caliphate—transcended Iraq’s borders, and, with its legions of foreign fighters, it remained an alien presence.
Conscious that the welcome might not last, Zarqawi decided to give his operation an Iraqi veneer. In January 2006, he formed the Mujahideen Shura Council (MSC), bringing together six mostly local Salafi (puritan Sunni) groups with an Iraqi as its nominal head. Three months later, Zarqawi was killed in a U.S. airstrike and MSC folded shortly thereafter. It was superseded in October 2006 by the Islamic State of Iraq (ISI).
But Sunnis resented interlopers like Zarqawi turning their political marginalization into an excuse for sectarian strife. They wanted a stake in Iraq’s future, not the endless insecurity that ISI guaranteed.
More here.