Calm largely returned to Balad by Tuesday, with Iraqi army troops forcing Shiite militia fighters out of police cars that the militiamen had commandeered for the attacks, said residents reached by telephone in the cut-off town. American troops patrolled the city and guarded one end of a Tigris River bridge that links Balad with Duluiyah, a Sunni farm town also at the epicenter of the outburst of sectarian conflict.On the Duluiyah end of the bridge, angry Sunni insurgents gathered in force, clutching their PKC machine guns and rocket launchers, standing their tense watch. Abu Achmed, a fighter in the Islamic Army, a Sunni insurgent movement, held a machine gun but wished for more.