I remember it starting very early like within 2-3 weeks (maybe 1 month) when the Iraqis hung those contractors from the bridge in Bagdad, I think it started before Saddam was captures (2-3 months later)... yep I was right... Invasion March 20th, Saddam captured Dec 14th... > 8 months later. Insurgency started long before that.
But it is hard to remember exact timelines 10 years later.
David (OFI)