Operation Tannenberg was closely followed by the '' Intelligenzaktion '' , a second phase of the '' Unternehmen Tannenberg '' directed by Heydrich 's '' Sonderreferat '' from Berlin . It lasted until January 1940 . In Pomerania alone , 36,000 – 42,000 Poles , including children , were killed before the end of 1939
Intelligenzaktion
Intelligenzaktion
Operation Tannenberg