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Picture
Moselle Treadway bridge, Mar 1945
bigpigeon.us webpage WWII Germany > The ETO > To the Rhine > Operation Undertone, © 2026 by Robert A. Christiansen, updated by RAC 4 Jan 2026
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During Operation Undertone, the US Seventh and Third Armies overran the southern Rhineland.
By 11 March 1945, as part of Operation Lumberjack, the US Third Army had cleared the Eifel in the northern Palatine north of the Moselle River. Almost all of the Rhine left bank was now in Allied hands, except for a salient extending upstream from Coblenz to Hagenau as shown on the following map. This area, bounded by the Moselle River on the west, the Rhine on the east, and the Siegfried Line on the south, was sometimes called the Rhine-Moselle Triangle. Within two weeks, Operation Undertone would remove this salient.

The US Seventh Army was charged with clearing the Rhine-Moselle Triangle. However, several issues impeded Seventh Army progress.​​
  • By mid-March, the Seventh Army had not regained all the northeastern France territory lost in the January German Nordwind attack.
  • Thus The Seventh Army was still short of the Siegfried Line.
  • The Siegfried Line in the Seventh Army sector was a formidable barrier.​
Considering these issues, the Seventh Army turned over additional portions of the Palatinate to the Third Army. The revised army boundary passed through Kaiserslautern as shown on the accompanying map. It was now understood that the Third Army would play a major role in the Seventh Army's pending offensive, Operation Undertone.

Operation Undertone officially began on 15 March and ended on 24 March. All three Seventh Army corps, with  the French First Army's Third Algerian Division on the right flank, began moving northward. XXI Corps in northern Lorraine on the left flank engaged the Siegfried Line first, followed by XV Corps in the middle and VI Corps on the right. German forces abandoned their positions, moving eastward through the fortified area.

Further north, starting on 11 March, all three Third Army corps drove south and east from the Moselle River, with the XX Corps passing through the road junction of Kaiserslautern on 20 March. Soon the Third Army occupied the bulk of the southern Palatinate. 
The Southern Palatinate
The Palatinate Cleared - status on 21 March
EmersonKent Scalable Version
The difficult to read map on the right contains additional information. You may be able to enlarge by clicking the red button, waiting for the alternative version to load, then positioning your cursor and clicking.
The Saar-Palatinate Triangle
The Saar-Palatinate Triangle, 12-21 Mar 1945
Preparing for the Rhine Crossings in the south:
  • On 19 March, the stage for the second Rhine crossing, by the Third Army at Oppenheim south of Mainz, was set.
  • As German resistance collapsed, XV Corps of the Seventh Army had access to a good highway from Zweibrücken northeast through Kaiserslautern and the Kaiserslautern gap to the Rhine, from which they could stage for their pending Rhine crossing near Worms.

The Southern Rhineland - a late March timeline:
  • 13 Mar - XX Corps, Third Army attacks SE from Saarburg bridgehead.
  • 14 Mar - XII Corps, Third Army crosses the Moselle.
  • 15 Mar - All three corps of the Seventh Army begins Operation Undertone attacking northward.
  • 16 Mar - VIII Corps, Third Army crosses the Moselle.
  • 19 Mar - VIII Corps completes capture of Koblenz.
  • 19 Mar - General Patton received permission for the Third Army to cross the Rhine. ​
  • 20 Mar - Elements of 4th Armored Division reach the Rhine at Worms; Third Army, XX Corps, captures Kaiserslautern.
  • 21 Mar - CCA of 6th Armored Div., XXI Corps, Seventh Army reaches Rhine at Rhein-Durkheim.
  • 21 Mar - Rhineland Campaign officially ends.
  • 22 Mar - Central Europe Campaign officially begins.
  • 22 Mar late - Third Army's first Rhine crossing, 5th Division, XII Corps at Oppenheim, begins.
  • 23 Mar - German withdrawal across Rhine in southern Palatinate begins.
  • 23 Mar - Third and Seventh Army units meet near Landau in eastern Palatine, trapping remaining German Siegfried Line units.
  • 24 Mar - Operation Undertone, Seventh Army offensive in southern Palatinate, officially ends.
  • 25 Mar - Major mopping up of rear guard and stragglers in southern Palatinate ends.
  • 27 Mar - French First Army sector is extended northward to Speyer.
Sources for Big Pigeon's WWII Germany > The ETO > To the Rhine > Operation Undertone webpage:
​Major Sources:Sources for webpage images: (C/O = Courtesy of)
Pottawattamie Area WWII Dead - WWII Germany > The ETO > To the Rhine > Operation Undertone: ​03-07 - WWII Germany > The ETO > To the Rhine > Operation Undertone:  (three dead, updated 30 Jun 2025)
  • Note that two of the below were casualties before Operation Undertone officially began on 15 March.
† Dinesen, Harold N., SN 37-433-094, US Army, Shelby Co.
  • Battery C., 400th AAA AW Bn., Seventh Army; WIA (sic, local newspaper) 12 Mar 1945, DNB (sic, War Dept. report) 15 Mar 1945 in hospital, France.
  • WWII >The ETO > To the Rhine > Operation Undertone
† Lindsay, William Larkin, SN 37-750-189, US Army, Pott. Co.
  • 275th Inf. Regt., 70th Inf. Div., XXI Corps, Seventh Army; KIA 16 Mar 1945 near Saarbrücken, Saarland, Germany.
  • WWII >The ETO > To the Rhine > Operation Undertone
† Rold, John Angus “Jack”, SN O-2007132, US Army, Cass Co., IA
  • Co. K, 276th Inf. Regt., 70th Inf. Div., XXI Corps, Seventh Army; DOW 8 Mar 1945 Forbach, near Saar River, Lorraine, France.
  • WWII >The ETO > To the Rhine > Operation Undertone