Since the bulk of Allied troops surrounding the Colmar Pocket were French, this mission was assigned to the French First Army. The U.S. 3rd Infantry Division had moved into the Vosges Mountains during mid-December to replace the worn-out U.S. 36th Infantry Division and so was already in place to support the reduction of the Colmar Pocket. Realizing the French would need the assistance of additional U.S. troops for the coming battle, General Jacob Devers, commander of the 6th Army Group, arranged for the transfer of a U.S. division from another part of the front. The U.S. 28th Infantry Division duly arrived from the Ardennes front and took up position along the right flank of the U.S. 3rd Infantry Division. With the 28th Division in the Kaysersberg Valley, the 3rd Division would be able to concentrate for an attack against two German divisions, the 708th "Volksgrenadier" and the 189th Infantry. Additionally, a U.S. armored division, the 10th, was scheduled to support the offensive, but as events developed, it was the U.S. 12th Armored Division that was eventually committed to the battle. The winter of 1944-45 was uncommonly cold for northwestern Europe. In his "History of the French First Army", General de Lattre described the weather in Alsace as "Siberian" with temperatures of -20 °C (-4 °F), strong winds, and over three feet (1 m) of snow. The Alsatian Plain is flat and offers an attacker practically no cover other than occasional woods. The plain is also a drainage basin for the Rhine and is consequently cut by many streams and drainage canals with alluvium-coated bottoms, making them treacherous for vehicles to ford. Dotting the plain are small villages made up of sturdy masonry houses whose multi-storey construction offered defending troops a commanding view of the surrounding fields. General Émile Béthouart's French I Corps (French: "Ier Corps d'Armée") attacked on 20 January 1945. The 2nd and 4th Moroccan Divisions had as their initial objective Ensisheim (). The 9th Colonial Division conducted secondary attacks on the right flank of the corps, north of Mulhouse. In support were tanks of the French 1st Armored Division. Attacking in a snowstorm, the French I Corps initially achieved tactical surprise against its opponent, General Erich Abraham's "LXIII.