In Dachau, as in other Nazi camps, German physicians performed medical experiments on prisoners, including high-altitude experiments using a decompression chamber, malaria and tuberculosis experiments, hypothermia experiments, and experiments testing new medications. Prisoners were also forced to test methods of making seawater potable and of halting excessive bleeding.
The industrialization and scale of the murder was unprecedented. Killings were systematically conducted in virtually all areas of occupied Europe—more than 20 occupied countries. Close to three million Jews in occupied Poland and between 700,000 and 2.5 million Jews in the Soviet Union were killed. Hundreds of thousands more died in the rest of Europe. Victims were transported in sealed freight trains from all over Europe to extermination camps equipped with gas chambers. The stationary facilities grew out of Nazi experiments with poison gas during the Aktion T4 mass murder ("euthanasia") programme against the disabled and mentally ill, which began in 1939. The Germans set up six extermination camps in Poland: Auschwitz II-Birkenau (established October 1941); Majdanek (October 1941); Chełmno (December 1941); and the three Operation Reinhard camps, Belzec, Sobibor, and Treblinka, in 1942. A seventh death camp, Maly Trostenets, was established near Minsk in Belarus, then part of the Reichskommissariat Ostland. Discussions at the Wannsee Conference in January 1942 made it clear that the German "final solution of the Jewish question" was intended eventually to include Britain and all the neutral states in Europe, including Ireland, Switzerland, Turkey, Sweden, Portugal, and Spain.
The camp was liberated on April 15, 1945, by the British 11th Armoured Division. The soldiers discovered approximately 60,000 prisoners inside, most of them half-starved and seriously ill, and another 13,000 corpses, including those of Anne and Margot Frank, lying around the camp unburied. The horrors of the camp, documented on film and in pictures, made the name "Belsen" emblematic of Nazi crimes in general for public opinion in many countries in the immediate post-1945 period. Today, there is a memorial with an exhibition hall at the site.