Macleans.ca article by Patrick Graham.

Ignore the sensationalistic title. Main thrust of the article is how the U.S. is increasingly backed by the Sunni elements that formed the backbone of the insurgency and Saddam's support, and moving away from Iranian-leaning Shi'i religious parties.

Long article with some highlights:

But watching Gen. Petraeus, I was struck by how familiar his words sounded. The general talked like every Sunni I’ve ever met in Iraq—hell, he sounded a bit like Saddam. The old tyrant would have had one of his characteristic chest-heaving guffaws watching Petraeus as he intoned the old Baathist mantra about the dangers to Iraq: Iran, Iran, Iran.
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It seems that Petraeus and Bush have come to the same conclusion as Saddam: the main enemy is Iran, and you can’t govern Iraq without the Sunni Arab tribes, even as you encourage anti-Iranian nationalism among the Shia. This is what Saddam did during the Iran-Iraq war of the 1980s, and what Washington is trying to do now. One of the main problems with this strategy is that both the Sunni tribes and Shia nationalists are profoundly anti-American and don’t trust each other—a potential recipe for further disaster.
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When the insurgency started in the summer of 2003, it was made up primarily of the same class of alienated Sunnis who are now part of the tribal Anbar Awakening. The insurgents I spent time with in 2003 and 2004 were, in essence, nationalists who didn’t like the U.S. Army driving around their villages, kicking down their doors and shooting their cousins at checkpoints. They were also deeply suspicious of American plans for democracy, because they feared it would lead to Iran taking over the government. Some hated Saddam, some liked him, but Saddam wasn’t the issue. For want of a better term, they are the equivalent of rednecks who believe in God, their country, and the right to bear arms.

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AMZ’s foreign fighters were never more than a tiny percentage of the insurgency, but they got all the credit, especially when their car bombs began killing civilians. Al-Qaeda in Iraq also had a tremendous appeal among the Sunni Iraqi underclass, just as Osama bin Laden’s al-Qaeda appeals to poor, angry Muslims the world over. Provinces like Anbar are very poor and very hierarchical, with a large and resentful social stratum at the bottom. Local Iraqis were drawn to al-Qaeda’s Salafist fundamentalism because it freed them from the conservative, tribal oppression that governed their lives. Al-Qaeda was able to take over some of the insurgency—and still controls chunks of Iraq—precisely because it was revolutionary, not conservative, and offered poor people in An­­bar a chance to kick some rich sheik and Baathist ass, as well as kill Americans and Shias. In part, al-Qaeda was part of a class war fuelled by profound anger and so­­cial resentment.

When my friend Ahmed, the grandson of an important sheik, invited me to “come kill some al-Qaeda” around Falluja, he didn’t mean hunt down Saudis who had trained in Afghanistan under bin Laden. He meant, “Let’s go shoot the uppity trash who took over my village.”

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The insurgents whom I knew at first tolerated al-Qaeda and its foreign volunteers, even though Salafism was alien to their beliefs in local Islamic traditions and their affinity toward the more mystical branch of Islam, Sufism, both anathema to Salafists. But al-Qaeda eventually turned against the other insurgent groups to consolidate its power, demanded their allegiance, and began killing anyone who opposed it or whom it thought might be a threat. In doing so, al-Qaeda extremists became like the Khmer Rouge, murdering any tribal sheik or former Iraqi military office or educated person not on their side (al-Qaeda’s attacks on the Sunni elite make many Sunnis believe that Iran, along with Syria, is funding the organization).