After the Battle of the Bulge, Seitz led CT 26 during operations to clear remaining German forces from positions in Belgium. Then on February 1–3, 1945, he directed an attack on the Siegfried Line or Westwall German border defenses on the German-Belgium border. The 26th Infantry Regiment broke through the German defenses to capture Hollerath, (Hellenthal-Hollerath), Germany. CT 26 under Seitz's command pushed on to cross the Roer River on February 25, 1945 and the Neffel Creek and Erft River by March 4, 1945. On March 8, the 16th United States Infantry Regiment and 18th United States Infantry Regiment captured Bonn, Germany, while the 26th Infantry Regiment secured the flank. On March 15, CT 26 crossed the Rhine River at the Remagen bridgehead and on March 17 began an attack to the northeast. On March 25, the 3rd Battalion, 26th Infantry Regiment and the 18th Infantry Regiment captured Ukerath, Germany, which was used as a base for the 1st Infantry Division's participation in the encirclement of the Ruhr Pocket. On April 9, 1945, Seitz was appointed to a brigadier general's position as assistant division commander of the 69th Infantry Division (United States). The 69th Infantry Division met the Soviet Union's 5th Guards Army at the Elbe River in Germany on April 25, 1945.