The radical Shiite cleric Moktada al-Sadr called for a national uprising against American and coalition forces today as a two-month truce between Mr. Sadr and the United States military appeared to collapse. In Baghdad and Basra, the largest city in southern Iraq, insurgents loyal to Mr. Sadr prepared for clashes with American and British troops. But heavy fighting appeared confined to Najaf, a Shiite holy city 100 miles south of Baghdad that is a Sadr stronghold. An American marine helicopter was shot down in Najaf this morning, although the crew was reported rescued.Full Story