Operation Undertone, also known as the Saar-Palatinate Offensive, was a large assault by the U.S. Seventh, Third, and French First Armies of the Sixth and Twelfth Army Groups as part of the Allied invasion of Germany in March 1945 during World War II. A force of three corps was to attack abreast from Saarbrücken, Germany, along a sector to a point southeast of Hagenau, France. A narrow strip along the Rhine leading to the extreme northeastern corner of Alsace at Lauterbourg was to be cleared by a division of the French First Army under operational control of the Seventh Army. The Seventh Army's main effort was to be made in the center up the Kaiserslautern corridor. In approving the plan, Supreme Allied Commander General Dwight D. Eisenhower asserted that the objective was not only to clear the Saar-Palatinate but to establish bridgeheads with forces of the Sixth Army Group over the Rhine between Mainz and Mannheim. The U.S. Third Army of the 12th Army Group was to be limited to diversionary attacks across the Moselle to protect the Sixth Army Group's left flank. Opposing commanders were U.S. General Jacob L. Devers, commanding U.S. Sixth Army Group and German SS General Paul Hausser, commanding German Army Group G. Significantly assisted by operations of the Third Army that overran German lines of communication, Operation Undertone cleared Wehrmacht defenses and pushed to the Rhine in the area of Karlsruhe within 10 days. General Devers′ victory—along with a rapid advance by the U.S. Third Army—completed the advance of Allied armies to the west bank of the Rhine along its entire length within Germany. The bulk of the text in this article is taken directly from The Last Offensive, a work of the U.S. Army that is in the public domain. The material was extracted from Chapter XII, The Saar-Palatinate, pp. 236–265. Plan Anticipating early completion of operations to clear the west bank of the Rhine north of the Moselle, Supreme Allied Commander General Dwight D. Eisenhower on 13 February 1945 had told his two American army group commanders—Generals Omar Bradley and Jacob L. Devers—to begin planning for a joint drive to sweep the Saar-Palatinate. Assigned a target date of 15 March, the offensive was to begin only after the 21st Army Group had reached the Rhine. It was to be designed both to draw enemy units from the north and to provide an alternate