David Cesarani emphasises the improvised, haphazard nature of Nazi policies in response to changing war time conditions in his overview, Final Solution: The Fate Of The European Jews 1933–49 (2016). "Cesarani provides telling examples", wrote Mark Roseman, "of a lack of coherence and planning for the future in Jewish policy, even when we would most expect it. The classic instance is the invasion of Poland in 1939, when not even the most elementary consideration had been given to what should happen to Poland's Jews either in the shorter or longer term. Given that Poland was home to the largest Jewish population in the world, and that, in a couple of years, it would house the extermination camps, this is remarkable."[118]
In 1935, Mengele earned a PhD in anthropology from the University of Munich.[7] In January 1937, he joined the Institute for Hereditary Biology and Racial Hygiene in Frankfurt, where he worked for Dr. Otmar Freiherr von Verschuer, a German geneticist with a particular interest in researching twins.[7] As von Verschuer's assistant, Mengele focused on the genetic factors that result in a cleft lip and palate, or a cleft chin.[10] His thesis on the subject earned him a cum laude doctorate in medicine (MD) from the University of Frankfurt in 1938.[11] (Both of his degrees were revoked by the issuing universities in the 1960s.)[12] In a letter of recommendation, von Verschuer praised Mengele's reliability and his ability to verbally present complex material in a clear manner.[13] The American author Robert Jay Lifton notes that Mengele's published works were in keeping with the scientific mainstream of the time, and would probably have been viewed as valid scientific efforts even outside Nazi Germany.[13]
Dr. Karski was the contact between the Polish resistance and the Polish government in exile. He repeatedly crossed enemy lines to act as a courier between his occupied nation and the West. Prior to his last departure from Poland, he was smuggled into the Warsaw Ghetto by the Jewish underground in order to witness the horrendous conditions. Asked to tell the story to the rest of the world, he reported on his experience to many world leaders, including American President Franklin Roosevelt.

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.
American soldiers stare down at a mass grave in Nordhausen concentration camp  © Originally a concentration camp for Polish political prisoners, Auschwitz was greatly expanded in 1941 with the addition of a much larger camp at nearby Birkenau. In all, Auschwitz-Birkenau and its sub-camps held 400,000 registered prisoners including 205,000 Jews, 137,000 Poles, 21,000 Gypsies, 12,000 Soviet POWs and 25,000 others (including a few British POWs). In this largest and worst of all the Nazi concentration camps, 210,000 prisoners died of starvation and abuse.
The logistics of the mass murder turned Germany into what Michael Berenbaum called a "genocidal state".[34] Eberhard Jäckel wrote in 1986 that it was the first time a state had thrown its power behind the idea that an entire people should be wiped out.[h] Anyone with three or four Jewish grandparents was to be exterminated,[36] and complex rules were devised to deal with Mischlinge ("mixed breeds": half and quarter Jews).[37] Bureaucrats identified who was a Jew, confiscated property, and scheduled trains to deport them. Companies fired Jews and later used them as slave labor. Universities dismissed Jewish faculty and students. German pharmaceutical companies tested drugs on camp prisoners; other companies built the crematoria.[34] As prisoners entered the death camps, they were ordered to surrender all personal property, which was catalogued and tagged before being sent to Germany for reuse or recycling.[38] Through a concealed account, the German National Bank helped launder valuables stolen from the victims.[39]
“The Nazis murdered between five million and six million Jews during the Holocaust, two-thirds of European Jewry and about one-third of the entire Jewish people. But a staggering 55 million may have perished in all theaters during the Second World War including some 20 million Soviet citizens…five million Germans, and three million non-Jewish Poles…In all, some 18 million European civilians may have died as a result of famine, disease, persecution, and more conventional acts of war.

Nazi persecution, arrests, and deportations were directed against all members of Jewish families, as well as many Gypsy families, without concern for age. Homeless, often orphaned, many children had frequently witnessed the murder of parents, siblings, and relatives. They faced starvation, illness, brutal labor, and other indignities until they were consigned to the gas chambers.
Over the years, Zeidel’s recalcitrance melted away. In the late 1970s, he sat for interviews with Lanzmann, a few minutes of which were included in the 1985 documentary Shoah. To Lanzmann, Zeidel confided that after his escape, he was sure he stunk of death. Later Zeidel agreed to participate in the making of Out of the Forest, a 2004 Israeli documentary about the role of Lithuanian collaborators in the mass killings at Ponar.
Executions by the Einsatzgruppen, mobile killing squads,were abandoned for practical reasons. Although approximately 1.5 million Jews had been shot by the winter of 1941, the Nazis felt that the efficiency of this slow and cumbersome method left much to be desired. Moreover, they found it was bad for the sol­diers’ morale. Himmler himself, commander of the SS and as such responsible for the annihilation of the Jews, was persuaded, after having witnessed such an execu­tion, that it badly affected the mental health of those carrying out the execution. The institutionalization of organized murder, founded on a division of labor and carried out in special installations expressly designed for this purpose, distanced the executioner from the victim, an indispensable psychological advantage in an enterprise of annihilation of such a huge scale.
In June 1941, Mengele was posted to Ukraine, where he was awarded the Iron Cross 2nd Class. In January 1942, he joined the 5th SS Panzer Division Wiking as a battalion medical officer. After rescuing two German soldiers from a burning tank, he was decorated with the Iron Cross 1st Class, the Wound Badge in Black, and the Medal for the Care of the German People. He was declared unfit for further active service in mid-1942, when he was seriously wounded in action near Rostov-on-Don. Following his recovery, he was transferred to the headquarters of the SS Race and Settlement Main Office in Berlin, at which point he resumed his association with von Verschuer, who was now director of the Kaiser Wilhelm Institute of Anthropology, Human Heredity, and Eugenics. Mengele was promoted to the rank of SS-Hauptsturmführer (captain) in April 1943.[20][21][22]