line of attack across the Rhine should the principal Allied drive in the north fail. The main effort, SHAEF planners contemplated, was to be made by the Sixth Army Group's Seventh Army, which was to be augmented by transferring one armored and three infantry divisions from the U.S. Third Army. During the first week of March, General Devers at Sixth Army Group approved a plan (Operation UNDERTONE) prepared by General Alexander Patch′s Seventh Army. A force of three corps was to attack abreast from Saarbrücken along a sector to a point southeast of Hagenau. 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. Eisenhower approved on 8 March, the same day that General George S. Patton obtained approval from General Bradley for the plan prepared by the Third Army staff for a major attack across the Moselle. The 12th Army Group commander in turn promoted the plan with General Eisenhower. Noting that the Germans had given no indication of withdrawing from the Siegfried Line in front of the Seventh Army and that General Patch thus might be in for a long, costly campaign, Bradley suggested that the Third Army jump the Moselle near Koblenz, sweep south along the west bank of the Rhine to cut the enemy's supply lines, and at the same time press from its previously established Saar-Moselle bridgehead near Trier to come at the Siegfried Line fortifications from the rear. General Eisenhower approved the plan without qualification. Although General Devers was briefly reluctant to endorse Third Army operations south of the Moselle lest the two forces become entangled with their converging thrusts, he too in the end approved the plan. He and Bradley agreed on a new boundary that afforded the Third Army a good road leading northeast