Half a year later, Harel was replaced by Meir Amit, who ordered the Mossad to “stop chasing after ghosts from the past and devote all our manpower and resources to threats against the security of the state.” He mandated that the agency deal with Nazis “only to the extent it is able to do so, in addition to its principal missions” and as long as “it doesn’t impinge on the other operations.”
By then, Palestinian terrorism had become Israel’s main security challenge, and the Mossad devoted most of its efforts to that threat. For the next 10 years, backed by Eshkol and his successors as prime minister, Golda Meir and Yitzhak Rabin, almost nothing was done about Mengele. The surge in terrorism, the surprise Yom Kippur War in 1973 and the Syrian military buildup with Soviet assistance took precedence.
Himmler assembled a force of about 3,000 men from Security Police, Gestapo, Kripo, SD, and the Waffen-SS, as the so-called "special commandos of the security forces" known as the Einsatzgruppen, to eliminate both communists and Jews in occupied territories. These forces were supported by 21 battalions of Orpo Reserve Police under Kurt Daluege, adding up to 11,000 men. The explicit orders given to the Order Police varied between locations, but for Police Battalion 309 participating in the first mass murder of 5,500 Polish Jews in the Soviet-controlled Białystok (a Polish provincial capital), Major Weiss explained to his officers that Barbarossa is a war of annihilation against Bolshevism, and that his battalions would proceed ruthlessly against all Jews, regardless of age or sex.
During the era of the Holocaust, German authorities also targeted other groups because of their perceived racial and biological inferiority: Roma (Gypsies), people with disabilities, and some of the Slavic peoples (Poles, Russians, and others). Other groups were persecuted on political, ideological, and behavioral grounds, among them Communists, Socialists, Jehovah's Witnesses, and homosexuals.
Twins were subjected to weekly examinations and measurements of their physical attributes by Mengele or one of his assistants. The experiments he performed on twins included unnecessary amputation of limbs, intentionally infecting one twin with typhus or some other disease, and transfusing the blood of one twin into the other. Many of the victims died while undergoing these procedures, and those who survived the experiments were sometimes killed and their bodies dissected once Mengele had no further use for them. Nyiszli recalled one occasion on which Mengele personally killed fourteen twins in one night by injecting their hearts with chloroform. If one twin died from disease, he would kill the other twin to allow comparative post-mortem reports to be produced for research purposes.
Victims usually arrived at the camps by freight train. Almost all arrivals at the Operation Reinhard camps of Treblinka, Sobibór, and Bełżec were sent directly to the gas chambers, with individuals occasionally selected to replace dead workers. At Auschwitz, camp officials usually subjected individuals to selections; about 25% of the new arrivals were selected to work. Those selected for death at all camps were told to undress and hand their valuables to camp workers. They were then herded naked into the gas chambers. To prevent panic, they were told the gas chambers were showers or delousing chambers. The procedure at Chełmno was slightly different. Victims there were placed in a mobile gas van and asphyxiated, while being driven to prepared burial pits in the nearby forests. There the corpses were unloaded and buried.
Anti-Semitism in Europe did not begin with Adolf Hitler. Though use of the term itself dates only to the 1870s, there is evidence of hostility toward Jews long before the Holocaust–even as far back as the ancient world, when Roman authorities destroyed the Jewish temple in Jerusalem and forced Jews to leave Palestine. The Enlightenment, during the 17th and 18th centuries, emphasized religious toleration, and in the 19th century Napoleon and other European rulers enacted legislation that ended long-standing restrictions on Jews. Anti-Semitic feeling endured, however, in many cases taking on a racial character rather than a religious one.
Although not ordered to take part, psychiatrists and many psychiatric institutions were involved in the planning and carrying out of Aktion T4 at every stage. After protests from the German Catholic and Protestant churches, Hitler ordered the cancellation of the T4 program in August 1941, although the disabled and mentally ill continued to be killed until the end of the war. The medical community regularly received bodies and body parts for research. Eberhard Karl University received 1,077 bodies from executions between 1933 and 1945. The neuroscientist Julius Hallervorden received 697 brains from one hospital between 1940 and 1944: "I accepted these brains of course. Where they came from and how they came to me was really none of my business."
Germany implemented the persecution of the Jews in stages. Following Adolf Hitler's appointment as German Chancellor in January 1933, the regime built a network of concentration camps in Germany for political opponents and those deemed "undesirable", starting with Dachau on 22 March 1933. After the passing of the Enabling Act on 24 March, which gave Hitler plenary powers, the government began isolating Jews from civil society, which included a boycott of Jewish businesses in April 1933 and enacting the Nuremberg Laws in September 1935. On 9–10 November 1938, during Kristallnacht (the "Night of Broken Glass"), Jewish businesses and other buildings were ransacked, smashed or set on fire throughout Germany and Austria, which Germany had annexed in March that year. After Germany invaded Poland in September 1939, triggering World War II, the regime set up ghettos to segregate Jews. Eventually thousands of camps and other detention sites were established across German-occupied Europe.
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. 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.