"The current Iraqi guerrilla war grew from a defeated hierarchical party-state structure. The army officer corps, Baathist party, and Fedayeen militia were secular state institutions drawn primarily from the ruling minority-Sunni Arab peoples. Much of the hierarchy and interrelations of the state structure remain intact in the remnant guerrilla organization. Foreign combatants, including al-Qaeda members and Chechens, have entered Iraq to fight the coalition. They do not blend in well, however, and many have since left or assumed specialized support roles such as bomb manufacturer, suicide bomber, or instructor. The Iraqi combatants have little experience in fighting as actual guerrillas, but some do have counterinsurgency experience against Kurds and Shia Iraqis. The insurgency has a strong urban component, particularly in Baghdad, Mosul, Fallujah, Al Sulaymaniyah, Samarra, and Tikrit. The rural guerrilla war is primarily restricted to the Sunni triangle west-northwest of Baghdad. The urban guerrillas rely primarily on improvised explosive devices (IEDs) because their marksmanship is not good. Iraqi guerrillas lack a ready sanctuary, but they are well funded with billions of U.S. dollars held by Iraq's former leaders."
U.S. Army Combined Arms Command: http://www.leavenworth.army.mil/
Military Review (July-August, 2004), v. 84 no. 5, p. 42-49