Wikipedia
Freikorps (, "Free Corps") were German volunteer units that existed from the 18th to the early 20th centuries, the members of which effectively fought as mercenaries, regardless of their own nationality. In German-speaking countries the first so-called Freikorps "free regiments" were formed in the 18th century from native volunteers, enemy renegades and deserters, and criminals. These sometimes exotically equipped units served as infantry and cavalry or, more rarely, as artillery. Sometimes in just company strength, sometimes in formations 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.
In the early 20th century, Freikorps were raised to fight against the newly formed Weimar Republic, as well as their left-wing counterparts, through the early 1920s. An entire series of Freikorps awards also existed, mostly replaced in 1933 by the Honor Cross for World War I veterans.