Wikipedia
Selbstschutz was a Nazi German paramilitary organisation formed after World War I for ethnic Germans who lived outside Germany. It operated in territories of Central and Eastern Europe before and after the beginning of World War II notably in Poland, the Free City of Danzig, Czechoslovakia and Ukraine. The ethnic German members of Selbstschutz were citizens of these countries. Notably, the name stands also for units of ethnic German, Austrian, and Swiss civil defence after World War II.
The first incarnation of the organisation aimed at returning Polish-inhabited territories back to Germany following the rebirth of Poland. In 1921, the units of Selbstschutz took part in the fights against the Polish Third Silesian Uprising. In 1938, a campaign was started by local Selbstschutz in the Czechoslovakian Sudetenland in order to subjugate the local Czechs prior to the Munich Conference.
During the Invasion of Poland of 1939, a number of similar units conducted sabotage actions directed by the emissaries trained in Nazi Germany. These groups were officially merged into one organization, the ethnic German Volksdeutscher Selbstschutz (Self-Defense Force) of more than 100,000 men. They took part in fighting the Poles as the Fifth Column, but also served as auxiliary forces of the Gestapo, SS and SD during the early stages of the occupation of Poland, and helped the Nazi administration in the newly formed Reichsgau Danzig-West Prussia and Reichsgau Wartheland. They served as local controllers, informers, and members of execution squads particularly active in the wave of mass murders of Polish intelligentsia during Operation Tannenberg and other more local and vengeful atrocities. The killings of Poles and Jews ascribed specifically to members of Volksdeutsche Selbstschutz is estimated at the minimum of 10,000 men, women and children. The force was disbanded in winter 1939/40 and the majority of its members joined the German SS or Gestapo by the spring of the following year.