Not so clear that that is how the "insurgency began". I would surmise that for the "insurgents" the insurgency began when the "infidel crusaders" set foot on "Muslim" soil. Further, that the insurgency is by and large made up of Sunni Muslims (i.e. its sectarian nature) it seems more likely that the Sunnis are resentful of losing their leader (Sadaam), fearful of living in a country ruled by those who endured sufferring and second-clbutt citizenship under them, and are desperately trying everything in their power to hold on to their "good old days", or even create new ones worse than the past.
This in fact explains the whole worldwide conflict that we see with Islam and the West - Muslims resorting to desperate measures to stop the increasing power and influence of Western civilisation as mankind moves forward, and instead to impose a medieval ideaology at any cost.
Syria and Iran are allied and obvious threats. No sane person can deny this. Isreal needs protection, the rantings of Iran's ruler prove this. Having oil in the hands of those for whom poverty of those under them is irrelevant is not good for anyone, anywhere. All this only considering that you premise is valid, of which there is no proof that it is.
So true, and so boggling, I am at a loss to comprehend their restraint in the face of such atrocity. I must admit that I am very wary of Islam and Muslims, but the more that world events unfold, the more I am inclined to believe that it is only the Sunni strain of Islam that is the perilous Fascist cancer that threatens Humanity. No offence.