The American military said Monday that it had killed as many as 18 supporters of the rebel Shiite Muslim cleric Moktada al-Sadr as it demolished his Baghdad headquarters during a heavy nighttime firefight that echoed around the capital. In clashes on Sunday, the military said, it killed another 18 of his militiamen, part of a mounting death toll of Mr. Sadr’s followers that included some 41 dead in a battle last week in Najaf, south of the capital. The director of a hospital in Sadr City, the poor Shiite neighborhood here where Mr. Sadr’s draws most of his support, said it had received nine bodies since Sunday, including that of a woman. Full Story