During World War II, Schramm volunteered again for service in the Wehrmacht and, given the rank of major, served in various staff positions until he was selected as the official staff historian, or diarist, for the German High Command Operational Staff ("Wehrmachtführungsstab"), replacing Helmuth Greiner, whose removal was orchestrated by Martin Bormann, the head of the Nazi Party chancellery. Schramm's duties involved keeping detailed records about the day-to-day activities and decisions of the General Staff, which included the top military field commanders in the German Army. This allowed Schramm unprecedented access to the highest echelons of the German military and its inner workings.