Tens of thousands were murdered in the German campaign of extermination of the Polish intelligentsia and other elements thought likely to resist ( e.g. Operation Tannenberg and Aktion AB ) . Catholic clergy were commonly imprisoned or otherwise persecuted and many ended up sent to their death in concentration camps . Tens of thousands of members of the resistance and others were tortured and executed at the Pawiak prison in Warsaw . From 1941 , disease and hunger also began to reduce the population , as the exploitation of resources and labor , terror and Germanisation reached greater intensity after the attack on the Soviet Union . Poles were also deported in large numbers to work as forced labor in Germany , or taken to concentration camps . About two million were transported to Germany to work as slaves and many died there . '' Łapanka '' or random roundup , on streets or elsewhere , was one of the methods practiced by the Nazis to catch prisoners for labor . Several hundred Wehrmacht brothels , for which local non-German women were forcibly recruited , operated throughout the Reich . In contrast to Nazi policies in occupied Western Europe , the Germans treated the Poles with intense hostility and all Polish state property and private industrial concerns were taken over by the German state . Poland was plundered and subjected to extreme economic exploitation throughout the war period
Operation Tannenberg
Operation Tannenberg
History of Poland (1939–1945)