Militias have always been in Iraq, and they comprise an integral part of modern Iraqi history. They have been prevalent among both state authorities and their opponents. The very definition of Iraqi political parties, particularly after the republic was founded in 1958, is tied to the idea of military wings, assassin groups, secret security attachés and their resistors.
In other words, 2003 wasn't the year militias were discovered in Iraq. Before April of that year, the most recent iterations of Iraqi militia were the foreign combatants employed by the authorities under the name “mujahideen” to fight American forces. Those were preceded by “Saddam’s Guerrillas” and ultimately split into new, ambiguous militias as a result of the American presence in Iraq.