Mengele, in distinctive white gloves, supervised the selection of Auschwitz’ incoming prisoners for either torturous labor or immediate extermination, shouting either “Right!” or “Left!” to direct them to their fate. Eager to advance his medical career by publishing “groundbreaking” work, he then began experimenting on live Jewish prisoners. In the guise of medical “treatment,” Mengele injected, or ordered others to inject, thousands of inmates with everything from petrol to chloroform to study the chemicals’ effects. Among other atrocities, he plucked out the eyes of Gypsy corpses to study eye pigmentation, and conducted numerous gruesome studies of twins.
Many Jews attempted to flee Germany, and thousands succeeded by immigrating to such countries as Belgium, Czechoslovakia, England, France and Holland. It was much more difficult to get out of Europe. Jews encountered stiff immigration quotas in most of the world's countries. Even if they obtained the necessary documents, they often had to wait months or years before leaving. Many families out of desperation sent their children first.
Mengele joined the Nazi Party in 1937 and the Schutzstaffel (SS; protection squadron) in 1938. He received basic training in 1938 with the Gebirgsjäger (light infantry mountain troop) and was called up for service in the Wehrmacht (Nazi armed forces) in June 1940, some months after the outbreak of World War II. He soon volunteered for medical service in the Waffen-SS, the combat arm of the SS, where he served with the rank of SS-Untersturmführer (second lieutenant) in a medical reserve battalion until November 1940. He was next assigned to the SS-Rasse- und Siedlungshauptamt (SS Race and Settlement Main Office) in Poznań, evaluating candidates for Germanization.[18][19]
Historians differ on the date of the decision to murder Jews systematically, the so-called “final solution to the Jewish question.” There is debate about whether there was one central decision or a series of regional decisions in response to local conditions. In either case, when Germany attacked the Soviet Union, its former ally, in June of 1941, the Nazis began the systematic killing of Jews.

The infamous 'Gate of Death' at Auschwitz II for the incoming freight trains was built of brick and cement mortar in 1943, and the three-track rail spur was added.[100] Until mid-August, 45,000 Thessaloniki Jews were murdered in a mere six months,[99] including over 30,000 Jews from Sosnowiec (Sosnowitz) and Bendzin Ghettos.[101] The spring of 1944 marked the beginning of the last phase of the Final Solution at Birkenau. The new big ramps and sidings were constructed, and two freight elevators were installed inside Crematoria II and III for moving the bodies faster. The size of the Sonderkommando was nearly quadrupled in preparation for the Special Operation Hungary (Sonderaktion Ungarn). In May 1944, Auschwitz-Birkenau became the site of one of the two largest mass murder operations in modern history, after the Großaktion Warschau deportations of the Warsaw Ghetto inmates to Treblinka in 1942. It is estimated that until July 1944 approximately 320,000 Hungarian Jews were gassed at Birkenau in less than eight weeks.[100] The entire operation was photographed by the SS.[102] In total, between April and November 1944, Auschwitz II received over 585,000 Jews from over a dozen regions as far as Greece, Italy, and France, including 426,000 Jews from Hungary, 67,000 from Łódź, 25,000 from Theresienstadt, and the last 23,000 Jews from the General Government.[103] Auschwitz was liberated by the Red Army on 27 January 1945, when the gassing had already stopped.[104]

The Nazis regarded the Slavs as subhuman, or Untermenschen.[426] In a secret memorandum dated 25 May 1940, Himmler stated that it was in German interests to foster divisions between the ethnic groups in the East. He wanted to restrict non-Germans in the conquered territories to schools that would only teach them how to write their own name, count up to 500, and obey Germans.[427][y] In November 1939 German planners called for "the complete destruction" of all Poles[430] and resettlement of the land by German colonists.[431] The Polish political leadership was the target of a campaign of murder (Intelligenzaktion and AB-Aktion).[432] Between 1.8 and 1.9 million non-Jewish Polish citizens perished at German hands during the course of the war; about four-fifths were ethnic Poles and the rest Ukrainians and Belarusians.[410] At least 200,000 died in concentration camps, around 146,000 in Auschwitz. Others died in massacres or in uprisings such as the Warsaw Uprising, where 120,000–200,000 were killed.[433] During the occupation, the Germans adopted a policy of restricting food and medical services, as well as degrading sanitation and public hygiene.[434] The death rate rose from 13 per 1000 before the war to 18 per 1000 during the war.[435] Around 6 million of World War II victims were Polish citizens; half the death toll were Jews.[436] Over the course of the war Poland lost 20 percent of its pre-war population.[436] Over 90 percent of the death toll came through non-military losses, through various deliberate actions by Germany and the Soviet Union.[433] Polish children were also kidnapped by Germans to be "Germanized", with perhaps as many as 200,000 children stolen from their families.[437]
  British troops guard Alex Pickowski, Camp Commandant of Dechau concentration camp  © The discovery of Belsen brought home the shocking truth about Nazi atrocities, but the facts had been known for some time. As early as the summer of 1941, British signals intelligence had intercepted and decoded radio messages from German police units co-operating with the Einsatzgruppen, and details of the killings of Jews were included in the monthly summaries that were sent to Churchill. Churchill responded with a speech on August 24 1941 in which he called the massacres 'a crime without a name' but erroneously identified the victims as 'Russian patriots defending their native soil'. Otherwise, these facts were not made public.

Browning also notes that the destruction of the Jews went hand-in-hand with a much wider attempt at “ethnic cleansing” throughout Eastern Europe. The Nazis had well-advanced plans, which might have been realized had they won the war, to remove by force millions of Poles and other Slavs to Siberia, with vast numbers certain to die en route. One of the major merits of Browning’s book is its detailed discussion of these plans, as well as Nazi policies towards the gypsies. Browning notes, correctly, that the Nazis killed large numbers of gypsies even though Hitler hardly ever mentioned them and certainly did not have anti-gypsy hostility at the heart of his ideology. Browning also offers a detailed consideration of the Nazi program of murdering the physically and mentally handicapped among “Aryan” Germans (the “T4 program”), which began in mid-1939 and eventually claimed seventy thousand victims before it was stopped in mid-1941, and he reports that many of the killers in the T4 program went on to be directly involved with the extermination of the Jews in Eastern Europe.
Medical experiments conducted on camp inmates by the SS were another distinctive feature.[51] At least 7,000 prisoners were subjected to experiments; most died as a result, during the experiments or later.[52] Twenty-three senior physicians and other medical personnel were charged at Nuremberg, after the war, with crimes against humanity. They included the head of the German Red Cross, tenured professors, clinic directors, and biomedical researchers.[53] Experiments took place at Auschwitz, Buchenwald, Dachau, Natzweiler-Struthof, Neuengamme, Ravensbrück, Sachsenhausen, and elsewhere. Some dealt with sterilization of men and women, the treatment of war wounds, ways to counteract chemical weapons, research into new vaccines and drugs, and the survival of harsh conditions.[52]

Inside the sealed-off ghettos, the Nazis reduced food rations to starvation level, an experience described by Sara Grossman, confined at age 21 in the Lodz ghetto: "I don't think anything hurts as much as hunger. You become wild. You are not responsible for what you say and what you do. You become an animal in the full meaning of the word. You prey on others. You will steal. That is what hunger does to us. It dehumanizes you. You're not a human being any more. Slowly, slowly the Germans were achieving their goal. I think they let us suffer from hunger, not because there was not enough food, but because this was their method of demoralizing us, of degrading us, of torturing us. These were their methods, and they implemented these methods scrupulously. Therefore we had very many, many deaths daily. Very many sick people for whom there was no medication, no help, no remedy. We just stayed there, and lay there, and the end was coming."
The ideology of Nazism brought together elements of antisemitism, racial hygiene, and eugenics, and combined them with pan-Germanism and territorial expansionism with the goal of obtaining more Lebensraum (living space) for the Germanic people.[16] Nazi Germany attempted to obtain this new territory by attacking Poland and the Soviet Union, intending to deport or kill the Jews and Slavs living there, who were considered by the Nazis to be inferior to the Aryan master race.[17]