After the Invasion of Poland ( 1 September 1939 ) , by Nazi Germany and the Soviet union , in occupied Poland each side proceeded to eliminate any possible resistance leader . In their part of occupied Poland , the Nazis began the Second World War ( 1939 – 45 ) with the extermination of the Polish intelligentsia , by way of the military operations of the Special Prosecution Book-Poland , the German AB-Aktion in Poland , the Intelligenzaktion , and the Intelligenzaktion Pommern . In their part of occupied Poland , the Soviet Union proceeded with the extermination of the Polish intelligentsia with operations such as the Katyn massacre ( 1940 ) , during which university professors , physicians , lawyers , engineers , teachers , writers and journalists were murdered
Intelligenzaktion
Intelligenzaktion
Intelligentsia