Marinebrigade Ehrhardt
Mauss volunteered for service in World War I in 1914 at the age of sixteen. He joined Lauenburger Jäger-Bataillon Nr. 9 of Ratzeburg, serving on the Western Front. In 1915, the youngest man in the division, he was awarded the Iron Cross, 2nd class as the best scout in the region during the Battle of the Somme. The following year, shortly after the transfer of his division to the Eastern Front, he received the Iron Cross, 1st class. Following World War I Mauss joined the paramilitary groups Freikorps Oberland and Marinebrigade Ehrhardt and fought against the Silesian Uprisings. Beginning in 1922, he studied dentistry at the University of Hamburg, attaining his doctorate in 1929 and opening a private dental practice. He re-enlisted in 1934, and reached the rank of major in April 1938.