BAGHDAD, Iraq – While American politicians and generals in Washington debate the possibility of civil war in Iraq, many U.S. officers and enlisted men who patrol Baghdad say it has already begun. Army troops in and around the capital interviewed in the last week cite a long list of evidence that the center of the nation is coming undone: Villages have been abandoned by Sunni and Shiite Muslims; Sunni insurgents have killed thousands of Shiites in car bombings and assassinations; Shiite militia death squads have tortured and killed hundreds, if not thousands, of Sunnis; and when night falls, neighborhoods become open battlegrounds. ‘There’s one street that’s the dividing line. They shoot mortars across the line and abduct people back and forth,’ said 1st Lt. Brian Johnson, a 4th Infantry Division platoon leader from Houston. Johnson, 24, was describing the nightly violence that pits Sunni gunmen from Baghdad’s Ghazaliyah neighborhood against Shiite gunmen from the nearby Shula district. As he spoke, the sights and sounds of battle grew: first, the rat-a-tat-tat of fire from AK-47 assault rifles, then the heavier bursts of PKC machine guns, and finally the booms of mortar rounds crisscrossing the night sky and crashing […]