BAGHDAD, Iraq -- In the deadliest reported firefight since the fall of Saddam Hussein's regime, U.S. soldiers fought back coordinated attacks Sunday using tanks, cannons and small arms in running battles throughout the northern city of Samarra. The troops killed 46 Iraqi fighters, and five Americans were wounded. Minutes later, two South Korean contractors were killed nearby in a roadside ambush in what U.S. officials called a new campaign aimed at undermining international support for the U.S.-led occupation of Iraq. Attacks on Saturday killed seven Spaniards, two Japanese diplomats and a Colombian oil worker. Lt. Col. William MacDonald of the...