U.S. troops raided a car bomb factory west of Baghdad with five buildings full of propane tanks and ordinary chemicals the military believes were to be used in bombs, a spokesman said Thursday, a day after insurgents blew up a truck carrying chlorine gas canisters. Maj. Gen. William Caldwell said the chlorine attack Wednesday — the second such “dirty” chemical attack in two days — signaled a change in insurgent tactics, and the military was fighting back with targeted raids. Full Story