BAGHDAD, Iraq, Jan. 11 - The story told by the two Iraqi guerrillas cut to the heart of the war that Iraqi and American officials now believe is raging inside the Iraqi insurgency. In October, the two insurgents said in interviews, a group of local fighters from the Islamic Army gathered for an open-air meeting on a street corner in Taji, a city north of Baghdad. Across from the Iraqis stood the men from Al Qaeda, mostly Arabs from outside Iraq. Some of them wore suicide belts. The men from the Islamic Army accused the Qaeda fighters of murdering their...