In the first three months of war , from the fall of 1939 until the spring of 1940 , some 60,000 former government officials , military officers in reserve , landowners , clergy , and members of the Polish intelligentsia were executed region by region in the so-called '' Intelligenzaktion '' , including over 1,000 POWs . Summary executions of Poles were conducted by all German forces without exception including , '' Wehrmacht '' , Gestapo , the SS and '' Selbstschutz '' in violation of international agreements . The mass killings were a part of the secretive Operation Tannenberg , an early measure of the '' Generalplan Ost '' settler colonization . Polish Christians as well as Jews were either murdered and buried in hastily dug mass graves or sent to prisons and German concentration camps . " Whatever we find in the shape of an upper class in Poland will be liquidated , " Hitler had ordered . In the '' Intelligenzaktion Pommern '' , a regional action in Pomeranian Voivodeship 23,000 Poles were killed . It was continued by the German AB-Aktion operation in Poland in the mid-1940s . The '' AB-Aktion '' saw the massacre of Lwów professors and the executions of about 1,700 Poles in the Palmiry forest . Several thousand civilian victims were executed or imprisoned . The '' Einsatzgruppen '' were also responsible for the indiscriminate killing of Jews and Poles during the 1941 German invasion of the Soviet Union
Intelligenzaktion Pommern
Intelligenzaktion Pommern
Nazi crimes against the Polish nation