 On 1 January 1937 he was appointed "Oberfähnrich zur See".After returning to Germany in February 1937 Maus several technical courses.On 1 April 1937 he was promoted to "Leutnant zur See" and returned to the cruiser "Nürnberg", where he served as adjutant from 3 March 1939 to 14 June 1939 and was promoted to "Oberleutnant zur See" on 1 April 1939.