Born in Diersburg, now part of Hohberg, Baden-Württemberg, he later joined the German Imperial Navy and served as a Korvettenkapitän. A strong opponent of the Treaty of Versailles, he developed strong monarchist views. During the period after the defeat of the German Empire, Ehrhardt formed the II.Marine Brigade. During the Beer Hall Putsch, Ehrhardt and his deputy commander Eberhard Kautter refused to have the league help Adolf Hitler's Nazi Party. Ehrhardt would later unsuccessfully contest the leadership with Hitler, but unlike their commander, most of Ehrhardt's men joined the Nazi Party.