The designation of Freikorps (German for "Free Corps", i.e. militia) was originally applied to voluntary armies. The first freikorps were recruited by Frederick II of Prussia in the eighteenth century during the Seven Years' War. Other known freikorps appeared during the Napoleonic Wars and were led for example by Ludwig Adolf Wilhelm von Lützow.

However, the meaning of the word has changed over time. After 1918, the term was used for the paramilitary organizations that sprang up around Germany as soldiers returned in defeat from World War I. They were the key Weimar paramilitary groups active during that time. Many German veterans felt profoundly disconnected from civilian life, and joined a Freikorps in search of stability within a military structure. Others, angry at their sudden, apparently inexplicable defeat, joined up in an effort to put down Communist uprisings or exact some form of revenge (see Dolchstoßlegende). They received considerable support from Gustav Noske, the German Defence Minister who used them to crush the Spartakist League with enormous violence, including the murders of Karl Liebknecht and Rosa Luxemburg on January 15, 1919. They were also used to put down the Munich Soviet Republic in 1919.

Some future members and, indeed, leaders of the Nazi Party were members of a Freikorps, including Ernst Röhm, future head of the Sturmabteilung or SA, and Rudolf Höß, the future Kommandant of Auschwitz.

In 1919-1920, Hitler had just begun his political career, as the leader of a tiny and as-yet-unknown party in Munich. Most Freikorps members, however, remained outsiders during the Third Reich. A frequent conversational topic amongst Freikorps veterans was, "Where was Hitler back in 1919/20, when we fought the Communists?".

VIA WIKIPEDIA