Many Jews were saved by hiding and also by illegal frontier crossings. Anne Frank‘s family hid in the concealed annex of an Amsterdam office building with the help of a Christian friend, and the family of Emmanuel Ringelblum (the Warsaw ghetto historian) hid in Warsaw in a specially prepared underground bunker camouflaged by a Polish gardener’s greenhouse. Both the Franks and the Ringelblums were caught and perished. About 20,000 Polish Jews, however, did survive hidden in Aryan Warsaw. Likewise, 5,000 Dutch Jews and several thousand German Jews were hidden in the heart of the Nazi empire, in Berlin and Hamburg.
"Righteous Gentiles of the Holocaust by David P. Gushee is an authoritative and indispensable exploration of a highly important aspect of the Holocaust, the willingness of a small, but morally significant, number of non-Jews to take on great risks for themselves and their families to rescue Jews from the Nazi death machine. In this well-documented, well-written book, Gushee explores the full range of Gentile responses to the plight of the Jews from overt hostility and obscene brutality to altruistic rescue, the better to understand the achievements of truly Righteous Gentiles. Highly recommended for anyone interested in the Holocaust."―Richard L. Rubenstein, President Emeritus, Distinguished Professor of Religion, University of Bridgeport
However, the capital of this bureaucratized and industrialized world of mass murders was Auschwitz. An operative concentration camp since May 1940, in the autumn of 1941 it was equipped with gas chambers. According to the latest estimates, the number of Jews killed in this camp approximated 1.5 million. In Auschwitz II (Birkenau), symbol and synonym of the Holocaust, the Nazi program of mass extermination reached its highest level of “perfection.”
With this police infrastructure in place, opponents of the Nazis were terrorized, beaten, or sent to one of the concentration camps the Germans built to incarcerate them. Dachau, just outside of Munich, was the first such camp built for political prisoners. Dachau's purpose changed over time and eventually became another brutal concentration camp for Jews.

But Auschwitz-Birkenau became more than a concentration camp. In the spring of 1942 gas chambers were built at Birkenau and mass transports of Jews began to arrive. Some of the new arrivals were inducted into the camp as registered prisoners, but the great majority were gassed immediately. These gassing operations were greatly expanded in the spring of 1943 with the construction of four purpose-built gas chamber and crematorium complexes, which included such refinements as electric lifts to carry bodies up to the crematoria. Each crematorium could handle 2,000 victims daily. In a nearby group of barracks, nicknamed 'Canada' by the prisoners, victims' belongings were sorted for transportation to the Reich. The victims' hair was used to stuff mattresses; gold teeth were melted down and the gold deposited to an SS account.

The SS used Sonderkommandos (Jewish slave laborers) during the gassing process to usher people in the undressing room and to clean up the gas chamber afterwards. One such survivor recalled the scene at Auschwitz: "There were all sorts of reactions from all sorts of people. There were disabled people. They would take out their war service cards showing that they had fought in the First World War with all kinds of distinctions and medals which they had from that time. They shouted, what's this? We fought for Germany. Now they're going to burn us, to kill us. This is impossible. We protest against such a thing. But everyone just laughed at them. Because they didn't take it seriously, these SS men. They laughed at the whole thing."

While concentration camps were meant to work and starve prisoners to death, extermination camps (also known as death camps) were built for the sole purpose of killing large groups of people quickly and efficiently. The Nazis built six extermination camps, all in Poland: Chelmno, Belzec, Sobibor, Treblinka, Auschwitz, and Majdanek. (Auschwitz and Majdanek were both concentration and extermination camps.)
The Nazis regarded the Slavs as subhuman, or Untermenschen.[426] In a secret memorandum dated 25 May 1940, Himmler stated that it was in German interests to foster divisions between the ethnic groups in the East. He wanted to restrict non-Germans in the conquered territories to schools that would only teach them how to write their own name, count up to 500, and obey Germans.[427][y] In November 1939 German planners called for "the complete destruction" of all Poles[430] and resettlement of the land by German colonists.[431] The Polish political leadership was the target of a campaign of murder (Intelligenzaktion and AB-Aktion).[432] Between 1.8 and 1.9 million non-Jewish Polish citizens perished at German hands during the course of the war; about four-fifths were ethnic Poles and the rest Ukrainians and Belarusians.[410] At least 200,000 died in concentration camps, around 146,000 in Auschwitz. Others died in massacres or in uprisings such as the Warsaw Uprising, where 120,000–200,000 were killed.[433] During the occupation, the Germans adopted a policy of restricting food and medical services, as well as degrading sanitation and public hygiene.[434] The death rate rose from 13 per 1000 before the war to 18 per 1000 during the war.[435] Around 6 million of World War II victims were Polish citizens; half the death toll were Jews.[436] Over the course of the war Poland lost 20 percent of its pre-war population.[436] Over 90 percent of the death toll came through non-military losses, through various deliberate actions by Germany and the Soviet Union.[433] Polish children were also kidnapped by Germans to be "Germanized", with perhaps as many as 200,000 children stolen from their families.[437]

Freund and I walked the path of the tunnel, over the large hummock of earth, out toward the surrounding pines. Not such a long distance on foot, perhaps, but positively heroic when one considered that it had been dug, night after night, by chained men who had spent their daylight hours laboring at their unthinkable task, subsisting on nothing more than gruel.
By the end of December 1941, before the Wannsee Conference, over 439,800 Jewish people had been murdered, and the Final Solution policy in the east became common knowledge within the SS.[44] Entire regions were reported "free of Jews" by the Einsatzgruppen. Addressing his district governors in the General Government on 16 December 1941, Governor-General Hans Frank said: "But what will happen to the Jews? Do you believe they will be lodged in settlements in Ostland? In Berlin, we were told: why all this trouble; we cannot use them in the Ostland or the Reichskommissariat either; liquidate them yourselves!"[45] Two days later, Himmler recorded the outcome of his discussion with Hitler. The result was: "als Partisanen auszurotten" ("exterminate them as partisans").[46] Israeli historian Yehuda Bauer wrote that the remark is probably as close as historians will ever get to a definitive order from Hitler for the genocide carried out during the Holocaust.[46] Within two years, the total number of shooting victims in the east had risen to between 618,000 and 800,000 Jews.[44][47]

In August 1944, they were discovered and deported to Nazi concentration camps. They were long thought to have been betrayed, although there are indications that their discovery may have been accidental, that the police raid had actually targeted "ration fraud".[14] Of the eight people, only Otto Frank, the oldest, survived the war. Anne died when she was 15 years old in Bergen-Belsen, from typhus. The exact date of her death is unknown, and has long been believed to be in early March, a few weeks before the prisoners were liberated by British troops in April 1945. However, research in 2015 indicated that Anne may have died in February.[15]
In the final months of the war, SS guards moved camp inmates by train or on forced marches, often called “death marches,” in an attempt to prevent the Allied liberation of large numbers of prisoners. As Allied forces moved across Europe in a series of offensives against Germany, they began to encounter and liberate concentration camp prisoners, as well as prisoners en route by forced march from one camp to another. The marches continued until May 7, 1945, the day the German armed forces surrendered unconditionally to the Allies.

Shortly after Hitler came to power, the Reichstag building, seat of the German parliament, burnt down. Communists were blamed for setting the fire and Hindenburg declared a state of emergency, passing the Reichstag Fire Decree that suspended basic rights like trial by jury. The German Communist Party was suspended and over 4,000 members were detained without trial. The next month, Hitler’s cabinet passed the Enabling Act which allowed him to enact laws without the consent of the parliament for four years, effectively transforming the German government into a de facto Nazi dictatorship.

The geographical patterns of local hostility to Jews influenced receptivity to their rescue. Thus, western Europe (France, Belgium, and the Netherlands), Scandinavia (Denmark and Finland), and southern Europe (Italy and Greece) adapted rapidly to the problems of hiding and rescuing Jews, whereas eastern and central Europe (Poland, the Ukraine, and Austria) remained a more hostile environment to rescue efforts.
In 1942, Auschwitz II (Birkenau), originally intended to house slave laborers, began to be used instead as a combined labor camp and extermination camp.[23][24] Prisoners were transported there by rail from all over German-occupied Europe, arriving in daily convoys.[25] By July 1942, SS doctors were conducting "selections" where incoming Jews were segregated, and those considered able to work were admitted into the camp while those deemed unfit for labor were immediately killed in the gas chambers.[26] The arrivals that were selected to die, about three-quarters of the total,[a] included almost all children, women with small children, pregnant women, all the elderly, and all of those who appeared (in a brief and superficial inspection by an SS doctor) to be not completely fit and healthy.[28][29]