In July 1940 Möser joined the staff at the newly opened SS-Hinzert concentration camp, infamous for its brutality, and later he transferred to Neuengamme. From May 1943 until October 1943 he was posted to the Auschwitz III Monowitz concentration camp as Kompanieführer of the Wachbatallion (Guard Battalion) in IG Farben's "Buna" plant. By the end of April 1944 he was also Kompanieführer of the Men on Watch at the Auschwitz I main camp (German: Stammlager).[1]