In November 1944, Hahn was reassigned from Warsaw to the Western Front. He was stationed in the town of Cochem and was appointed commander of "Einsatzgruppe L" which was attached to the German Sixth Panzer Army during the Battle of the Bulge. After the failure of the Ardennes offensive in January 1945, Hahn was transferred to Army Group Vistula on the Eastern Front where he served as a representative of the "Sicherheitsdienst" on the staff of "SS-Obergruppenfuhrer" Carl Oberg during the Vistula-Oder offensive. In February 1945, he was posted to Dresden as "Stabsführer" (chief of staff) to "SS-Gruppenführer" Ludolf von Alvensleben, the Higher SS and Police Leader for the Elbe.