Lead elements of the Army's 3rd Infantry Division pushed through a gap west of Karbala after a nightlong bombardment of the Shiite holy city some 50 miles from Saddam's seat of power.
The U.S. forces were up against the Republican Guard's Medina and Nebuchadnezzar divisions and also attacked towns and positions north of Karbala where 2,000 Fedayeen loyalists and Baath Party members were believed to be hunkered down.
At least 20 Iraqis were killed, and an unknown number of fighters were taken prisoner, field reports said. No U.S. casualties were reported. One tank belonging to the Nebuchadnezzar Division was reported destroyed.
Army Lt. Col. Scott Rutter, a battalion commander, said Iraqi troops concentrated their attacks on his unit, allowing the rest of the brigade to pass through the Karbala gap unscathed. The gap is a choke point between a lake to the west and the city of Karbala to the east that opens onto a plain.
Iraqi defenders fired anti-aircraft guns into the sky most of the night, as U.S. artillery pounded suspected military positions in the ancient town. B-52 bombers circled Karbala throughout the night, carpet-bombing some areas while fighter jets went after small targets.
Pentagon officials have said the Republican Guard must be eliminated before ground troops move on Baghdad. For more than a week, coalition airstrikes and artillery barrages have pounded Republican Guard units to the south, west and north of the capital.
Military officials have said that the Medina Division's fighting strength has been reduced by more than half.