Coalition Warplanes Hit Baghdad Defenses By DAVID ESPO .c The Associated Press U.S.-led warplanes and helicopters attacked Republican Guard units defending Baghdad on Monday while ground troops advanced to within 50 miles of the Iraqi capital. White House aides said a down payment on war-related costs would come to $75 billion. Five days into Operation Iraqi Freedom, fierce resistance prevented American and British forces from securing the southern cities of Basra and An Nasiriyah and thwarted efforts to extinguish burning oil wells. Iraq claimed custody, as well, of two American pilots after a helicopter went down, in addition to a...