Stein began in the lower ranks of the Volunteer Corps of Luxembourg, which he entered on the 7 of August 1905, before being promoted to Lieutenant on October 18, 1909.[2] On the 31 of January 1915, Maurice was attached to the Gendarme, and placed issued the position of military district commander for Diekirch.[2][5]
Stein oversaw the Gendarmes at the time of the German invasion of Luxembourg in 1940.[6] Prior to the outbreak of hostilities, a series of nine radio outposts were established along the German border, each manned by gendarmes, with a central radio receiver in Captain Stein's official office near the volunteers' Saint-Esprit Barracks in the capital.[7]
