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.
Killing on a mass scale using gas chambers or gas vans was the main difference between the extermination and concentration camps.[269] From the end of 1941, the Germans built six extermination camps in occupied Poland: Auschwitz II-Birkenau, Majdanek, Chełmno, and the three Operation Reinhard camps at Belzec, Sobibor, and Treblinka II.[44][270] Maly Trostenets, a concentration camp in the Reichskommissariat Ostland, became a killing centre in 1942.[44] Gerlach writes that over three million Jews were murdered in 1942, the year that "marked the peak" of the mass murder of Jews.[271] At least 1.4 million of these were in the General Government area of Poland.[272]
The German occupation authorities carried out shooting operations of Jews and others they deemed to be potential enemies of permanent German rule in the east; these operations lasted until the Germans evacuated the Soviet Union in the first half of 1944. The SS and police often did not have sufficient manpower to carry out these operations, so they were assisted whenever necessary by local auxiliaries whom they recruited and by units of the German armed forces. The Germans and their collaborators killed between 1.0 and 1.5 million Jews in shooting operations or in gas vans in the occupied Soviet Union

In his 1965 essay "Command and Compliance", which originated in his work as an expert witness for the prosecution at the Frankfurt Auschwitz Trials, the German historian Hans Buchheim wrote there was no coercion to murder Jews and others, and all who committed such actions did so out of free will. Buchheim wrote that chances to avoid executing criminal orders "were both more numerous and more real than those concerned are generally prepared to admit",[468] and that he found no evidence that SS men who refused to carry out criminal orders were sent to concentration camps or executed.[469] Moreover, SS rules prohibited acts of gratuitous sadism, as Himmler wished for his men to remain "decent"; acts of sadism were carried out on the initiative of those who were either especially cruel or wished to prove themselves ardent National Socialists.[468] Finally, he argued that those of a non-criminal bent who committed crimes did so because they wished to conform to the values of the group they had joined and were afraid of being branded "weak" by their colleagues if they refused.[470]
In October 1941 the Nazis began turning the concentration camp at Majdanek into a death camp as well. They then began the construction of killing centres at Bełżec, Treblinka, near Warsaw, and at Sobibór. The first mass gassing of Jews began in Chelmno on 8 December 1941, when the Nazis used gas vans to murder people from the Łódź ghetto. The Nazis also ordered the expansion of the Auschwitz camp complex to increase the capacity for murder.
Over the decades that followed, ordinary Germans struggled with the Holocaust’s bitter legacy, as survivors and the families of victims sought restitution of wealth and property confiscated during the Nazi years. Beginning in 1953, the German government made payments to individual Jews and to the Jewish people as a way of acknowledging the German people’s responsibility for the crimes committed in their name.
Meanwhile they waited, trying with all their strength to survive just one more day – the slave laborers, the fortunate few still not discovered – and those confined in ghettos such as the teenager who wrote in her diary: “When we look at the fence separating us from the rest of the world, our souls, like birds in a cage, yearn to be free. How I envy the birds that fly to freedom.”

Beginning in late 1941, the Germans began mass transports from the ghettoes in Poland to the concentration camps, starting with those people viewed as the least useful: the sick, old and weak and the very young. The first mass gassings began at the camp of Belzec, near Lublin, on March 17, 1942. Five more mass killing centers were built at camps in occupied Poland, including Chelmno, Sobibor, Treblinka, Majdanek and the largest of all, Auschwitz-Birkenau. From 1942 to 1945, Jews were deported to the camps from all over Europe, including German-controlled territory as well as those countries allied with Germany. The heaviest deportations took place during the summer and fall of 1942, when more than 300,000 people were deported from the Warsaw ghetto alone.
In his bunker, in the Chancellory building in Berlin, knowing that the war was lost and that the “1,000 Year Reich” had lasted only a few years, Hitler committed suicide hours after marrying Eva Braun. Germany formally surrendered to the Allies on May 7, 1945. By the end of the war, more than 55 million had died and 35 million wounded. Only 17 million of the dead were soldiers.

How, when, and why the Nazis’ decision to exterminate Europe’s Jews was made remains one of the most vexed and disputed of all important questions concerning the Holocaust. There was not simply an order from Hitler commanding the killing of the Jews, and there is general agreement that the genocide evolved in stages, steadily becoming more comprehensive. The Origins of the Final Solution by the universally respected historian Christopher R. Browning, now at the University of North Carolina at Chapel Hill, is a magisterial examination of this subject in the wider context of the overall evolution of Nazi policy towards the Jews between the outbreak of the Second World War in September 1939 and the opening of the first extermination camps early in 1942.

The outbreak of war and the invasion of Poland brought a population of 3.5 million Polish Jews under the control of the Nazi and Soviet security forces,[14] and marked the start of a far more savage persecution, including mass killings.[6] In the German-occupied zone of Poland, Jews were forced into hundreds of makeshift ghettos, pending other arrangements.[15] Two years later, with the launch of Operation Barbarossa against the USSR in late June 1941, the German top echelon began to pursue Hitler's new anti-Semitic plan to eradicate, rather than expel, Jews.[16] Hitler's earlier ideas about forcible removal of Jews from the German-controlled territories in order to achieve Lebensraum were abandoned after the failure of the air campaign against Britain, initiating a naval blockade of Germany.[7] Reichsführer-SS Heinrich Himmler became the chief architect of a new plan, which came to be called The Final Solution to the Jewish Question.[17] On 31 July 1941, Reichsmarschall Hermann Göring wrote to Reinhard Heydrich (Himmler's deputy and chief of the RSHA),[18][19] instructing Heydrich to submit concrete proposals for the implementation of the new projected goal.[20]
Similarly, in Ordinary Men (1992), Christopher Browning examined the deeds of German Reserve Police Battalion 101 of the Ordnungspolizei ("order police"), used to commit massacres and round-ups of Jews, as well as mass deportations to the death camps. The members of the battalion were middle-aged men of working-class background from Hamburg, who were too old for regular military duty. They were given no special training. During the murder of 1,500 Jews from Józefów in Poland, their commander allowed them to opt out of direct participation. Fewer than 12 men out of a battalion of 500 did so. Influenced by the Milgram experiment on obedience, Browning argued that the men killed out of peer pressure, not bloodlust.[471]
Szeptycki (also spelled Sheptytskyi) was a member of the Polish Catholic hierarchy who ordered that the clergy reporting to him act to save Jews. At first, Andrey worked with his brother Abbot Kliment to help a Jewish boy, Kurt Lewin, whose parents had been murdered by the Nazi's by keeping him safe in one of their monasteries in western Ukraine. During the course of the Holocaust, Szeptycki saved a number of Jews by allowing them to find shelter within the monasteries affiliated with the Greek Catholic Church.
While the labour camps at Auschwitz and Majdanek used inmates for slave labour to support the German war effort, the extermination camps at Belzec, Treblinka, and Sobibor had one task alone: killing. At Treblinka a staff of 120, of whom only 30 were SS (the Nazi paramilitary corps), killed some 750,000 to 925,000 Jews during the camp’s 17 months of operation. At Belzec German records detail a staff of 104, including about 20 SS, who killed some 500,000 Jews in less than 10 months. At Sobibor they murdered between 200,000 and 250,000. These camps began operation during the spring and summer of 1942, when the ghettos of German-occupied Poland were filled with Jews. Once they had completed their missions—murder by gassing, or “resettlement in the east,” to use the language of the Wannsee protocols—the Nazis closed the camps. There were six extermination camps, all in German-occupied Poland, among the thousands of concentration and slave-labour camps throughout German-occupied Europe.

Like most “scientists” at work in the concentration camp environment, Mengele enlisted the aid of trained medical professionals among the prisoner population to perform the more grisly, or mundane, tasks and to carry out autopsies upon his dead victims. Much of our early knowledge of Mengele's activities at Auschwitz comes from Dr. Miklos Nyiszli, a prisoner-physician who assisted Mengele under duress. Nyiszli published his experiences, initially in his native Hungarian, in 1946. His work Auschwitz: A Doctor's Eyewitness Account appeared in English in 1960.

On 6 January 1942, the Soviet Minister of Foreign Affairs, Vyacheslav Molotov, sent out diplomatic notes about German atrocities. The notes were based on reports about bodies surfacing from poorly covered graves in pits and quarries, as well as mass graves found in areas the Red Army had liberated, and on witness reports from German-occupied areas.[335] The following month, Szlama Ber Winer escaped from the Chełmno concentration camp in Poland, and passed detailed information about it to the Oneg Shabbat group in the Warsaw Ghetto. His report, known by his pseudonym as the Grojanowski Report, had reached London by June 1942.[288][336] Also in 1942, Jan Karski sent information to the Allies after being smuggled into the Warsaw Ghetto twice.[337][s] On 27 April 1942, Vyacheslav Molotov sent out another note about atrocities.[335] In late July or early August 1942, Polish leaders learned about the mass killings taking place inside Auschwitz. The Polish Interior Ministry prepared a report, Sprawozdanie 6/42,[340] which said at the end:

In the German parliament, the Nazi party, led by Adolf Hitler, gained popularity. The number of seats Nazis controlled in the parliament rose from 12 in 1928 to 230 in 1932, making them the largest political party. The strong showing guaranteed the Nazi party would need to be part of any political coalition. Believing he could check Hitler’s ambition, President Hindenburg reluctantly made Hitler the Chancellor of Germany on January 30, 1933.
Mengele's eye experiments included attempts to change the eye color by injecting chemicals into the eyes of living subjects, and he killed people with heterochromatic eyes so that the eyes could be removed and sent to Berlin for study.[53] His experiments on dwarfs and people with physical abnormalities included taking physical measurements, drawing blood, extracting healthy teeth, and treatment with unnecessary drugs and X-rays.[3] Many of his victims were dispatched to the gas chambers after about two weeks, and their skeletons sent to Berlin for further analysis.[54] Mengele sought out pregnant women, on whom he would perform experiments before sending them to the gas chambers.[55] Witness Vera Alexander described how he sewed two Romani twins together, back to back, in a crude attempt to create conjoined twins;[50] both children died of gangrene after several days of suffering.[56]