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.