Hitler believed that before monotheism and the Jewish ethical vision came along, the world operated according to the laws of nature and evolution: survival of the fittest. The strong survived and the weak perished. When the lion hunts the herd the young, the sick and weak are always the first victims. Nature is brutal but nature is balanced. There is no mercy. So too in antiquity-the great empires-the Babylonians, Greeks and Romans conquered, subjugated and destroyed other peoples. They respected no borders and showed no mercy. This too Hitler viewed as natural and correct. But in a world operating according to a Divinely-dictated ethical system—where a God-given standard applies and not anyone’s might—the weak did not need to fear the strong. As Hitler saw it, the strong were emasculated-this was neither normal nor natural and in Hitler’s eyes, the Jews were to blame.
 “I would do it all again.” Edeltrud Posiles uttered these words in 2011 when she was the last surviving Righteous Gentile who had hid Jews in Nazi Austria. When Posiles – then Becher – heard a knock on the door in 1942, she opened it to find her Jewish fiancé and his two brothers on her doorstep. As described at the DailyMail.com, “Hiding Jews was punishable by death. But the feisty 94-year old [said] ‘there was never a moment’s doubt in my mind,’ when asked if she hesitated as she was asked by the brothers for sanctuary.”
The diary is not a genial document, despite its author’s often vividly satiric exposure of what she shrewdly saw as “the comical side of life in hiding.” Its reputation for uplift is, to say it plainly, nonsensical. Anne Frank’s written narrative, moreover, is not the story of Anne Frank, and never has been. That the diary is miraculous, a self-aware work of youthful genius, is not in question. Variety of pace and tone, insightful humor, insupportable suspense, adolescent love pangs and disappointments, sexual curiosity, moments of terror, moments of elation, flights of idealism and prayer and psychological acumen—all these elements of mind and feeling and skill brilliantly enliven its pages. There is, besides, a startlingly precocious comprehension of the progress of the war on all fronts. The survival of the little group in hiding is crucially linked to the timing of the Allied invasion. Overhead the bombers, roaring to their destinations, make the house quake; sometimes the bombs fall terrifyingly close. All in all, the diary is a chronicle of trepidation, turmoil, alarm. Even its report of quieter periods of reading and study express the hush of imprisonment. Meals are boiled lettuce and rotted potatoes; flushing the single toilet is forbidden for ten hours at a time. There is shooting at night. Betrayal and arrest always threaten. Anxiety and immobility rule. It is a story of fear.

According to scholars Christian Gerlach and Peter Monteath, among others, the pivotal moment for Hitler’s decision came on December 12, 1941, at a secret meeting with some 50 Nazi officials, including Joseph Goebbels (Nazi minister of propaganda) and Hans Frank (governor of occupied Poland). Though no written documents of the meeting survive, Goebbels described the meeting in his journal on December 13, 1941:

Lengyel described how Dr. Mengele would take all the correct medical precautions while delivering a baby at Auschwitz, yet only a half hour later, he would send the mother and baby to be gassed and burned in the crematorium. Lengyel herself was selected for the gas chamber, but managed to break away from the group of women who had been selected, before the truck arrived to take the prisoners to the crematorium.
But this week the Israeli courts waded into the process of selecting who to include on the list of righteous gentiles at the Yad Vashem Holocaust memorial in Jerusalem amid a campaign to add two Germans - one of them a convicted war criminal who was at the centre of a recent Hollywood film - and to strike off a Ukrainian who Jewish survivors say has no place among heroes.
By the end of 1934 Hitler was in absolute control of Germany, and his campaign against the Jews in full swing. The Nazis claimed the Jews corrupted pure German culture with their "foreign" and "mongrel" influence. They portrayed the Jews as evil and cowardly, and Germans as hardworking, courageous, and honest. The Jews, the Nazis claimed, who were heavily represented in finance, commerce, the press, literature, theater, and the arts, had weakened Germany's economy and culture. The massive government-supported propaganda machine created a racial anti-Semitism, which was different from the long­standing anti-Semitic tradition of the Christian churches.

^ Jump up to: a b Dan Stone (Histories of the Holocaust, 2010): "Europe's Romany (Gypsy) population was also the victim of genocide under the Nazis. Many other population groups, notably Poles, Ukrainians, and Soviet prisoners of war were killed in huge numbers, and smaller groups such as Jehovah's Witnesses, Black Germans, and homosexuals suffered terribly under Nazi rule. The evidence suggests that the Slav nations of Europe were also destined, had Germany won the war, to become victims of systematic mass murder; and even the terrible brutality of the occupation in eastern Europe, especially in Poland, can be understood as genocidal according to the definition put forward by Raphael Lemkin in his major study, Axis Rule in Occupied Europe (1944), the book that introduced the term 'genocide' to our vocabulary. Part of the reason for today's understanding, though, is a correct assessment of the fact that for the Nazis the Jews were regarded in a kind of 'metaphysical' way; they were not just considered as racially inferior (like Romanies), deviants (like homosexuals) or enemy nationals standing in the way of German colonial expression (like Slavs). ... [T]he Jews were to some extent outside of the racial scheme as defined by racial philosophers and anthropologists. They were not mere Untermenschen (sub-humans) ... but were regarded as a Gegenrasse: "a 'counter-race', that is to say, not really human at all. ... 'Holocaust', then, refers to the genocide of the Jews, which by no means excludes an understanding that other groups—notably Romanies and Slavs—were victims of genocide. Indeed ... the murder of the Jews, although a project in its own right, cannot be properly historically situated without understanding the 'Nazi empire' with its grandiose demographic plans."[32]
The Nazis brought their own strain of radical ruthlessness to these ideas. They glorified war and saw the uncompromising struggle for survival between nations and races as the engine of human progress. They rejected morality as a Jewish idea, which had corrupted and weakened the German people. They maintained that a great nation such as Germany had the right and duty to build an empire based on the subjugation of 'inferior races'. They looked eastwards to Poland and Russia (where, as it happened, the great majority of European Jews lived) for the territorial expansion of their 'living space' (Lebensraum).
Mengele's work also involved carrying out selections, a task that he chose to perform even when he was not assigned to do so, in the hope of finding subjects for his experiments,[33] with a particular interest in locating sets of twins.[34] In contrast to most of the other SS doctors, who viewed selections as one of their most stressful and unpleasant duties, he undertook the task with a flamboyant air, often smiling or whistling a tune.[35][31] He was also one of the SS doctors responsible for supervising the administration of Zyklon B, the cyanide-based pesticide that was used for the mass killings in the Birkenau gas chambers. He served in this capacity at the gas chambers located in crematoria IV and V.[36]