sentences:  On 20 March 1945, after five days of combat, the corps broke through the Siegfried Line and captured Saarbrücken.Crossing the Rhine behind the U.S. XV Corps in Operation Undertone, the XXI Corps captured Würzburg on 5 April 1945, after a three-day battle marked by an assault across the Main River.Facing determined opposition, the corps fought its way into Schweinfurt on 12 April 1945, after five days of battle.