Under the rule of Adolf Hitler, the persecution and segregation of Jews was implemented in stages. After the Nazi Party achieved power in Germany in 1933, its state-sponsored racism led to anti-Jewish legislation, economic boycotts, and the violence of the Kristallnacht ("Night of Broken Glass") pogroms, all of which aimed to systematically isolate Jews from society and drive them out of the country.
On July 17, 1941, four weeks after the invasion of the Soviet Union, Hitler tasked SS chief Heinrich Himmler with responsibility for all security matters in the occupied Soviet Union. Hitler gave Himmler broad authority to physically eliminate any perceived threats to permanent German rule. Two weeks later, on July 31, 1941, Nazi leader Hermann Goering authorized SS General Reinhard Heydrich to make preparations for the implementation of a "complete solution of the Jewish question."
In 1944, Josiah DuBois, Jr. wrote a memorandum to then-Secretary of the Treasury Henry Morgenthau, Jr. entitled “Report to the Secretary on the Acquiescence of This Government in the Murder of the Jews”, which condemned the bureaucratic interference of U.S. State Department policies in obstructing the evacuation of Holocaust Refugees from Romania and Occupied France. The Report would spur the Roosevelt administration to create the War Refugee Board later that year.
When Germany invaded Poland in September 1939, it gained control of about 2 million Jews in the occupied territory. The rest of Poland was occupied by the Soviet Union, which had control of the rest of Poland's pre-war population of 3.3–3.5 million Jews.[141] German plans for Poland included expelling gentile Poles from large areas, confining Jews, and settling Germans on the emptied lands.[142] The Germans initiated a policy of sending Jews from all territories they had recently annexed (Austria, Czechoslovakia, and western Poland) to the central section of Poland, which they called the General Government. There, the Jews were concentrated in ghettos in major cities,[143] chosen for their railway lines to facilitate later deportation.[144] Food supplies were restricted, public hygiene was difficult, and the inhabitants were often subjected to forced labor.[145] In the work camps and ghettos, at least half a million Jews died of starvation, disease, and poor living conditions.[146] Jeremy Black writes that the ghettos were not intended, in 1939, as a step towards the extermination of the Jews. Instead, they were viewed as part of a policy of creating a territorial reservation to contain them.[147][l]
When the Nazi’s rose to power they built facilities to hold and, eventually kill, their enemies. When the first concentration camps were built in 1933, this primarily meant political dissidents and opponents of the Nazi government, such as German Communists, Socialists, Social Democrats but would grow to include asocial groups – Gypsies, Jehovah’s Witnesses, the homeless, the mentally ill and homosexuals.  It was not until Kristallnacht that the prisoners became primarily Jewish.

By the end of September, the SS had started to develop plans to deport Jews to newly invaded Poland: the first steps towards the systematic murder that would follow. In Poland itself, thousands of Poles and Jews were rounded up and shot, early indications of the systematic murder that would follow. Alongside this, Hitler approved a new programme of euthanasia to exterminate the handicapped and mentally ill.
Not long after beginning the survey of the site, Freund and his team confirmed the existence of a previously unmarked burial pit. At 80 feet across and 15 feet deep, the scientists calculated that the grave contained the cremated remains of as many as 7,000 people. The researchers also released the preliminary results of their search for the tunnel, along with a series of ERT-generated cross sections that revealed the tunnel’s depth beneath the ground’s surface (15 feet at points) and its dimensions: three feet by three feet at the very widest, not much larger than a human torso. From the entrance inside the bunker to the spot in the forest, now long grown over, where the prisoners emerged measured more than 110 feet. At last, there was definitive proof of a story known until now only in obscure testimonies made by a handful of survivors—a kind of scientific witness that transformed “history into reality,” in the words of Miri Regev, Israel’s minister of culture, who highlighted the importance of documenting physical evidence of Nazi atrocities as a bulwark against “the lies of the Holocaust deniers.”
Our many Jewish friends and acquaintances are being taken away in droves. The Gestapo is treating them very roughly and transporting them in cattle cars to Westerbork. . . .The people get almost nothing to eat, much less to drink, as water is available only one hour a day, and there’s only one toilet and sink for several thousand people. Men and women sleep in the same room, and women and children often have their heads shaved. . . . If it’s that bad in Holland, what must it be like in those faraway and uncivilized places where the Germans are sending them? We assume that most of them are being murdered. The English radio says they’re being gassed.
Yugoslavia and Greece were invaded in April 1941 and surrendered before the end of the month. Germany and Italy divided Greece into occupation zones but did not eliminate it as a country. Yugoslavia, home to around 80,000 Jews, was dismembered; regions in the north were annexed by Germany and regions along the coast made part of Italy. The rest of the country was divided into the Independent State of Croatia, nominally an ally of Germany, and Serbia, which was governed by a combination of military and police administrators.[167] According to historian Jeremy Black, Serbia was declared free of Jews in August 1942.[168] Croatia's ruling party, the Ustashe, killed the country's Jews, and killed or expelled Orthodox Christian Serbs and Muslims.[167] Jews and Serbs alike were "hacked to death and burned in barns", according to Black. One difference between the Germans and Croatians was that the Ustashe allowed its Jewish and Serbian victims to convert to Catholicism so they could escape death.[168]
The Nazi invasion of the Soviet Union codenamed Operation Barbarossa, which commenced on 22 June 1941, set in motion a "war of destruction" which quickly opened the door to systematic mass murder of European Jews.[30] For Hitler, Bolshevism was merely "the most recent and most nefarious manifestation of the eternal Jewish threat".[31] On 3 March 1941, Wehrmacht Joint Operations Staff Chief Alfred Jodl repeated Hitler's declaration that the "Jewish-Bolshevik intelligentsia would have to be eliminated" and that the forthcoming war would be a confrontation between two completely opposing cultures.[32] In May 1941, Gestapo leader Heinrich Müller wrote a preamble to the new law limiting the jurisdiction of military courts in prosecuting troops for criminal actions because: "This time, the troops will encounter an especially dangerous element from the civilian population, and therefore, have the right and obligation to secure themselves."[33]
Genealogical Studies in the Cases of Cleft Lip-Jaw-Palate (1938), his medical dissertation, earned him a doctorate in medicine from Frankfurt University. Studying the influence of genetics as a factor in the occurrence of this deformity, Mengele conducted research on families who exhibited these traits in multiple generations. The work also included notes on other abnormalities found in these family lines.[7][122]
Before the the Final Solution the plan the Nazis had was to force the Jews to immigration. In 1940 the nazis planed to ship the Jews to an Island in the Indian ocean called Madagascar. it was not until later they referred to the Final Solution as genocide rather than territorial Final Solution. As the nazis were under cover of the war they developed technology to successfully murder millions of Jews. details were worked out at the Wansee Conference. All Jews in Germanys occupied countries were sent to ghettos as holding areas. Many were sent to camps were they worked under brutal conditions. Many were sent to gas chambers. As the Allies advanced death marches cut down the number of potential survivors. Some of Hitler's objectives were to wage to wars at once one aimed at anyone who objected him the other at the Jews. Hitler's success was credited to planed steps and reaction to those of other world powers. 

Mengele was an attractive man. A perennial little smile showed the gap between his front teeth. Immaculately dressed in jodhpurs, he wore a cap bearing the SS insignia and carried the obligatory riding crop, constantly slapping it against his gleaming black boots. Whenever he spoke to me, he was very polite, giving the impression that he was interested in me. It was hard to believe that his little smile and courteous behavior were just a facade behind which he devised the most horrific murderous schemes.
When war erupted, Mengele was a medical officer with the SS, the elite squad of Hitler’s bodyguards who later emerged as a secret police force that waged campaigns of terror in the name of Nazism. In 1943, Mengele was called to a position that would earn him his well-deserved infamy. SS head Heinrich Himmler appointed Mengele the chief doctor of the Auschwitz death camps in Poland.
Browning believes that the "Final Solution as it is now understood—the systematic attempt to murder every last Jew within the German grasp"[5] took shape during a five-week period, from 18 September to 25 October 1941. During this time: the sites of the first extermination camps were selected, different methods of killing were tested, Jewish emigration from the Third Reich was forbidden, and 11 transports departed for Łódź as a temporary holding station. During this period, Browning writes, "The vision of the Final Solution had crystallised in the minds of the Nazi leadership, and was being turned into reality."[5] This period was the peak of Nazi victories against the Soviet Army on the Eastern Front, and, according to Browning, the stunning series of German victories led to both an expectation that the war would soon be won, and the planning of the final destruction of the "Jewish-Bolshevik enemy".[114]
After Germany’s loss in WWI, the Treaty of Versailles punished Germany by placing tough restrictions on the country. The treaty made Germany take full responsibility for the war, reduced the extent of German territory, severely limited the size and placement of their armed forces, and forced Germany to pay the allied powers reparations. These restrictions not only increased social unrest but, combined with the start of the Great Depression, collapsed the German economy as inflation rose alongside unemployment.

Yet any projection of Anne Frank as a contemporary figure is an unholy speculation: it tampers with history, with reality, with deadly truth. “When I write,” she confided, “I can shake off all my cares. My sorrow disappears, my spirits are revived!” But she could not shake off her capture and annihilation, and there are no diary entries to register and memorialize the snuffing of her spirit. Anne Frank was discovered, seized, and deported; she and her mother and sister and millions of others were extinguished in a program calculated to assure the cruellest and most demonically inventive human degradation. The atrocities she endured were ruthlessly and purposefully devised, from indexing by tattoo through systematic starvation to factory-efficient murder. She was designated to be erased from the living, to leave no grave, no sign, no physical trace of any kind. Her fault—her crime—was having been born a Jew, and as such she was classified among those who had no right to exist: not as a subject people, not as an inferior breed, not even as usable slaves. The military and civilian apparatus of an entire society was organized to obliterate her as a contaminant, in the way of a noxious and repellent insect. Zyklon B, the lethal fumigant poured into the gas chambers, was, pointedly, a roach poison.

According to the testimony of Rudolf Hoess at the Nuremberg International Military Tribunal in 1946, Reichsführer-SS Heinrich Himmler gave repeated orders that the staff members at the concentration camps were forbidden "to lay violent hands on the prisoners." According to the survivors of Birkenau, Dr. Mengele frequently lost his temper and beat the prisoners, yet he was never punished by his superior officers.

Historians find it difficult to determine precisely when the first concerted effort at annihilation of all Jews began in the last weeks of June 1941 during Operation Barbarossa.[63] Dr. Samuel Drix (Witness to Annihilation), Jochaim Schoenfeld (Holocaust Memoirs), and several survivors of the Janowska concentration camp, who were interviewed in the film Janovska Camp at Lvov, among other witnesses, have argued that the Final Solution began in Lwów (Lemberg) in Distrikt Galizien of the General Government during the German advance across Soviet-occupied Poland. Statements and memoirs of survivors emphasize that, when Ukrainian nationalists and ad hoc Ukrainian People's Militia (soon reorganized as the Ukrainian Auxiliary Police) began to murder women and children, rather than only male Jews, the "Final Solution" had begun. Witnesses have said that such murders happened both prior to and during the pogroms reportedly triggered by the NKVD prisoner massacre. The question of whether there was some coordination between the Lithuanian and Ukrainian militias remains open (i.e. collaborating for a joint assault in Kovno, Wilno, and Lwów).[63]

Mengele's research subjects were better fed and housed than the other prisoners, and temporarily spared from execution in the gas chambers.[42] He established a kindergarten for children who were the subjects of his experiments, as well as the preschool children from the Romani camp. The facility provided better food and living conditions than other areas of the camp, and included a children's playground.[43] When visiting his young subjects, he introduced himself as "Uncle Mengele" and offered them sweets,[44] while at the same time being personally responsible for the deaths of an unknown number of victims whom he killed via lethal injection, shootings, beatings, and his deadly experiments.[45] In his 1986 book, Lifton describes Mengele as sadistic, lacking empathy, and extremely antisemitic, believing the Jews should be eliminated entirely as an inferior and dangerous race.[46] Rolf Mengele later claimed that his father had shown no remorse for his wartime activities.[47]