<P> On 31 July 1941 Hermann Göring gave written authorization to SS - Obergruppenführer Reinhard Heydrich, Chief of the Reich Main Security Office (RSHA), to prepare and submit a plan for a "total solution of the Jewish question" in territories under German control and to coordinate the participation of all involved government organisations . The resulting Generalplan Ost (General Plan for the East) called for deporting the population of occupied Eastern Europe and the Soviet Union to Siberia, for use as slave labour or to be murdered . </P> <P> Towards the end of the war, the camps became sites for medical experiments . Eugenics experiments, freezing prisoners to determine how downed pilots were affected by exposure, and experimental and lethal medicines were all tried at various camps . A cold water immersion experiments at Dachau concentration camp were performed by Sigmund Rascher . </P> <P> The lead editors of the Encyclopedia of Camps and Ghettos, 1933--1945 of the United States Holocaust Memorial Museum, Geoffrey Megargee and Martin Dean, cataloged some 42,500 Nazi ghettos and camps throughout Europe, spanning German - controlled areas from France to Russia and Germany itself, operating from 1933 to 1945 . They estimate that 15 million to 20 million people died or were imprisoned in the sites . </P> <P> Some of the most notorious slave labour camps included a network of subcamps . Gross - Rosen had 100 subcamps, Auschwitz had 44 subcamps, Stutthof had 40 sub-camps set up contingently . Prisoners in these subcamps were dying from starvation, untreated disease and summary executions by the tens of thousands already since the beginning of war . </P>

How many concentration camps were there in world war 2