motto Arbeit macht frei ("Work brings freedom"). Only high-ranking officials knew that one of the purposes of some of the camps, known as extermination camps (or death camps), was mass murder of the undesirable minorities; officially the prisoners were used in enterprises such as production of synthetic rubber, as was the case of a plant owned by IG Farben, whose laborers came from Auschwitz III camp, or Monowitz. Laborers from concentration camps were literally worked to death. in what was known as extermination through labor. Auschwitz received the first contingent of 728 Poles on 14 June 1940, transferred from an overcrowded prison at Tarnów. Within a year the Polish inmate population was in thousands, and begun to be exterminated, including in the first gassing experiment in September 1941. According to Polish historian Franciszek Piper, approximately 140,000–150,000 Poles went through Auschwitz, with about half of them perishing there due to executions, medical experiments, or due to starvation and disease. About 100,000 Poles were imprisoned in Majdanek camp, with similar fatality rate. About 30,000 Poles died at Mauthausen, 20,000 at Sachsenhausen and Gross-Rosen each, 17,000 at Neuengamme and Ravensbrueck each, 10,000 at Dachau, and tens of thousands perished in other camps and prisons. The Holocaust Following the invasion of Poland in 1939 most of the approximately 3.5 million Polish Jews were rounded up and put into newly established ghettos by Nazi Germany. The ghetto system was unsustainable, as by the end of 1941 the Jews had no savings left to pay the SS for food deliveries and no chance to earn their own keep. At 20 January 1942 Wannsee Conference, held near Berlin, new plans were outlined for the total genocide of the Jews, known as the "Final Solution of the Jewish Question". The extermination program was codenamed Operation Reinhard. Three secret extermination camps set up specifically for Operation Reinhard; Treblinka, Belzec and Sobibor. In addition to the Reinhard camps, mass killing facilities such as gas chambers using Zyklon B were added to the Majdanek concentration camp in March 1942 and at Auschwitz and Chełmno. Cultural genocide Nazi Germany engaged in a concentrated effort to destroy Polish culture. To that end, numerous cultural and educational institutions were closed or destroyed, from schools and universities, through monuments and libraries, to laboratories and museums. Many employees of said institutions were arrested and executed as part wider persecutions of Polish intellectual elite. Schooling of Polish