The plan was finalized in May 1939 by the Central Office II P (Poland).
Following the orders of Adolf Hitler, a special unit dubbed Tannenberg was created within the Reich Main Security Office (Reichssicherheitshauptamt).
It commanded a number of Einsatzgruppen units formed with Gestapo, Kripo and Sicherheitsdienst (SD) officers and men who were theoretically to follow the Wehrmacht (armed forces) into occupied territories.
Their task was to track down and arrest all the people listed on the proscription lists exactly as it had been compiled before the outbreak of war.

The first phase of the action occurred in August 1939 when about 2,000 activists of Polish minority organisations in Germany were arrested and murdered.
The second phase of the action began on September 1, 1939, and ended in October, resulting in at least 20,000 deaths in 760 mass executions by Einsatzgruppen special task units with help from regular Wehrmacht units.
A special formation was created from the German minority living in Poland called Selbstschutz, whose members had trained in Germany before the war in diversion and guerilla fighting (see: Deutscher Volksverband, the German People's Union in Poland).
The formation was responsible for many massacres and due to its bad reputation was dissolved by Nazi authorities after the September Campaign with transfer to regular formations.
The plan was finalized in May 1939 by the Central Office II P (Poland). Following the orders of Adolf Hitler, a special unit dubbed Tannenberg was created within the Reich Main Security Office (Reichssicherheitshauptamt). It commanded a number of Einsatzgruppen units formed with Gestapo, Kripo and Sicherheitsdienst (SD) officers and men who were theoretically to follow the Wehrmacht (armed forces) into occupied territories. Their task was to track down and arrest all the people listed on the proscription lists exactly as it had been compiled before the outbreak of war.
The first phase of the action occurred in August 1939 when about 2,000 activists of Polish minority organisations in Germany were arrested and murdered. The second phase of the action began on September 1, 1939, and ended in October, resulting in at least 20,000 deaths in 760 mass executions by Einsatzgruppen special task units with help from regular Wehrmacht units. A special formation was created from the German minority living in Poland called Selbstschutz, whose members had trained in Germany before the war in diversion and guerilla fighting (see: Deutscher Volksverband, the German People's Union in Poland). The formation was responsible for many massacres and due to its bad reputation was dissolved by Nazi authorities after the September Campaign with transfer to regular formations.
Operation Tannenberg