Wikipedia
Intelligenzaktion (, intelligentsia action) was a highly secretive genocidal action of Nazi Germany against Polish elites (primarily intelligentsia; teachers, doctors, priests, community leaders etc.) in the early stages of World War II. It was conducted as part of attempted complete Germanization of western regions of occupied Poland before their planned annexation. The operation took the lives of 100,000 Poles according to Institute of National Remembrance. Most victims were massacred in remote locations in mass disappearances, and buried in clandestine grave pits. Selected few were executed openly in order to inflict terror on the general population before expulsions. The executioners from Einsatzgruppen der Sicherheitspolizei und des SD and Selbstschutz worked under the guise of elimination of potentially dangerous elements.
The German Intelligenzaktion was a major step in the implementation of the Sonderaktion Tannenberg (Operation Tannenberg a.k.a. Unternehmen Tannenberg) of installing Nazi officials from SiPo, Kripo, Gestapo and SD at the helm of an administrative machine in occupied Poland, leading to the Generalplan Ost colonization. Some 61,000 Polish targets came from special lists created in advance. The Intelligenzaktion took place soon after the German invasion of Poland, lasting from fall of 1939 till spring of 1940. It was continued by the murderous German AB-Aktion operation in Poland.