Sixth United States Army Group in the context of "Brenner Pass"

The Colmar Pocket (French: Poche de Colmar; German: Brückenkopf Elsass) was the area held in central Alsace, France, by the German Nineteenth Army from November 1944 to February 1945, against the U.S. 6th Army Group (6th AG) during World War II. It was formed when 6th AG liberated southern and northern Alsace and adjacent eastern Lorraine, but could not clear central Alsace. During Operation Nordwind in December 1944, the 19th Army attacked north out of the Pocket in support of other German forces attacking south from the Saar into northern Alsace. In late January and early February 1945, the French First Army (reinforced by the U.S. XXI Corps) cleared the Pocket of German forces.

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 75-kilometre (47 mi) 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.