After the war, Mülverstedt joined the Sicherheitspolizei on 15 September 1919 (later redesignated the Schutzpolizei) as a Hauptmann, and was assigned to posts in Berlin, Eiche, and Erfurt.
In March 1943 they were taken into an underground bunker in Potsdam-Eiche and then in March 1945 to the salt mine at Bernterode in Eichsfeld (Thüringen).