Hermann Ehrhardt was a German naval officer in World War I who became an anti-republican and anti-Semitic German nationalist Freikorps leader during the Weimar Republic. As head of the Marine Brigade Ehrhardt, he was among the best-known Freikorps leaders in the immediate postwar years. The Brigade fought against the local soviet republics that arose during the German Revolution of 1918–1919 and later was among the key players in the anti-democratic Kapp Putsch of March 1920. After the Brigade's forced disbanding, Ehrhardt used the remnants of his unit to found the Organisation Consul, a secret group that committed numerous politically motivated assassinations. After it was banned in 1922, Ehrhardt formed other less successful groups such as the Bund Viking. Because of his opposition to Adolf Hitler, Ehrhardt was forced to flee Germany in 1934 and lived apolitically in Austria until his death in 1971.

Freikorps were irregular German and other European military volunteer units, or paramilitary, that existed from the 18th to the early 20th centuries. They effectively fought as mercenaries or private military companies, regardless of their own nationality. In German-speaking countries, the first so-called Freikorps were formed in the 18th century from native volunteers, enemy renegades, and deserters. These sometimes exotically equipped units served as infantry and cavalry ; sometimes in just company strength and sometimes in formations of up to several thousand strong. There were also various mixed formations or legions. The Prussian von Kleist Freikorps included infantry, jäger, dragoons and hussars. The French Volontaires de Saxe combined uhlans and dragoons.