Historians differ on the date of the decision to murder Jews systematically, the so-called “final solution to the Jewish question.” There is debate about whether there was one central decision or a series of regional decisions in response to local conditions. In either case, when Germany attacked the Soviet Union, its former ally, in June of 1941, the Nazis began the systematic killing of Jews.
At the end of the war, between 50,000 and 100,000 Jewish survivors were living in three zones of occupation: American, British and Soviet. Within a year, that figure grew to about 200,000. The American zone of occupation contained more than 90 percent of the Jewish displaced persons (DPs). The Jewish DPs would not and could not return to their homes, which brought back such horrible memories and still held the threat of danger from anti-Semitic neighbors. Thus, they languished in DP camps until emigration could be arranged to Palestine, and later Israel, the United States, South America and other countries. The last DP camp closed in 1957 (David S. Wyman, "The United States," in David S. Wyman, ed., The World Reacts to the Holocaust, Baltimore, MD: Johns Hopkins University Press, 1996, pp. 707­10).
Meanwhile, sightings of Josef Mengele were being reported all over the world. Wiesenthal claimed to have information that placed Mengele on the Greek island of Kythnos in 1960,[103] in Cairo in 1961,[104] in Spain in 1971,[105] and in Paraguay in 1978, eighteen years after he had left the country.[106] He insisted as late as 1985 that Mengele was still alive—six years after he had died—having previously offered a reward of US$100,000 in 1982 for the fugitive's capture.[107] Worldwide interest in the case was heightened by a mock trial held in Jerusalem in February 1985, featuring the testimonies of over one hundred victims of Mengele's experiments. Shortly afterwards, the West German, Israeli, and U.S. governments launched a coordinated effort to determine Mengele's whereabouts. The West German and Israeli governments offered rewards for his capture, as did The Washington Times and the Simon Wiesenthal Center.[108]

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]

——— (2015). "Is the "Final Solution" Unique?". The Third Reich in History and Memory. London: Abacus. ISBN 978-0-349-14075-9. Revised and extended from Richard Evans (2011). "Wie einzigartig war die Ermordung der Juden durch die Nationalsocialisten?" in Günter Morsch and Bertrand Perz (eds). Neue Studien zu nationalsozialistischen Massentötungen durch Giftgas: Historische Bedeutung, technische Entwicklung, revisionistische Leugnung. Berlin: Metropol Verlag, pp. 1–10. ISBN 9783940938992
Estimates of Jewish participation in partisan units throughout Europe range from 20,000 to 100,000.[323] In the occupied Polish and Soviet territories, thousands of Jews fled into the swamps or forests and joined the partisans,[324] although the partisan movements did not always welcome them.[325] An estimated 20,000 to 30,000 joined the Soviet partisan movement.[326] One of the famous Jewish groups was the Bielski partisans in Belarus, led by the Bielski brothers.[324] Jews also joined Polish forces, including the Home Army. According to Timothy Snyder, "more Jews fought in the Warsaw Uprising of August 1944 than in the Warsaw Ghetto Uprising of April 1943".[327][r]
Perhaps the main area of dispute about this process concerns Hitler’s precise role in ordering the killing of the Jews. Remarkably, we simply do not know, in an unequivocal way, what Hitler’s precise role was. The dictator often gave oral orders to senior henchmen such as Heinrich Himmler that were never written down, and historians can only infer Hitler’s precise role and intentions from evidence which is infuriatingly inadequate and contradictory. Because of the lack of unambiguous evidence, historians have been divided for decades, rather misleadingly, into so-called “intentionalists,” who argue that Hitler always intended to kill the Jews, and “functionalists,” who claim that the killing process somehow, as it were, welled up from local SS units in Russia until it became general Nazi policy.
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]
In June 1941 Germany attacked the Soviet Union and began the "Final Solution." Four mobile killing groups were formed called Einsatzgruppen A, B, C and D. Each group contained several commando units. The Einsatzgruppen gathered Jews town by town, marched them to huge pits dug earlier, stripped them, lined them up, and shot them with automatic weapons. The dead and dying would fall into the pits to be buried in mass graves. In the infamous Babi Yar massacre, near Kiev, 30,000-35,000 Jews were killed in two days. In addition to their operations in the Soviet Union, the Einsatzgruppen conducted mass murder in eastern Poland, Estonia, Lithuania and Latvia. It is estimated that by the end of 1942, the Einsatzgruppen had murdered more than 1.3 million Jews.
Friday, August 1, marks the 70th anniversary of Anne Frank's final diary entry. Three days later, she was arrested with her family in the "secret annex" of a house in Amsterdam, Netherlands, where they had hidden for two years. She later died at the Bergen-Belsen concentration camp when she was 15. In her diary, Anne describes a 1942 picture of herself: "This is a photo as I would wish myself to look all the time. Then I would maybe have a chance to come to Hollywood." Click through the gallery to see other pages from her diary:

Browning also notes that the destruction of the Jews went hand-in-hand with a much wider attempt at “ethnic cleansing” throughout Eastern Europe. The Nazis had well-advanced plans, which might have been realized had they won the war, to remove by force millions of Poles and other Slavs to Siberia, with vast numbers certain to die en route. One of the major merits of Browning’s book is its detailed discussion of these plans, as well as Nazi policies towards the gypsies. Browning notes, correctly, that the Nazis killed large numbers of gypsies even though Hitler hardly ever mentioned them and certainly did not have anti-gypsy hostility at the heart of his ideology. Browning also offers a detailed consideration of the Nazi program of murdering the physically and mentally handicapped among “Aryan” Germans (the “T4 program”), which began in mid-1939 and eventually claimed seventy thousand victims before it was stopped in mid-1941, and he reports that many of the killers in the T4 program went on to be directly involved with the extermination of the Jews in Eastern Europe. 

In May, Nazis under the direction of SS Lt. Colonel Adolf Eichmann boldly began a mass deportation of the last major surviving population of European Jews. From May 15 to July 9, over 430,000 Hungarian Jews were deported to Auschwitz. During this time, Auschwitz recorded its highest-ever daily number of persons killed and cremated at just over 9000. Six huge open pits were used to burn the bodies, as the number of dead exceeded the capacity of the crematories.
In 1942, fifteen Nazi leaders met at a conference in Wannsee, Germany to discuss the “Jewish Question”. Their job was to decide the most efficient way to exterminate the Jews. They decided that Jews would be sent to extermination camps where they would be sent to showers. But instead of water coming out of the faucet, they faced their death when poisonous Zyklon-B gas leaked through the showerheads to suffocate them. This decision at the conference is called the “Final Solution.”
During the era of the Holocaust, German authorities also targeted other groups because of their perceived racial and biological inferiority: Roma (Gypsies), people with disabilities, and some of the Slavic peoples (Poles, Russians, and others). Other groups were persecuted on political, ideological, and behavioral grounds, among them Communists, Socialists, Jehovah's Witnesses, and homosexuals.

"For the survivor who chooses to testify, it is clear: his duty is to bear witness for the dead and the living. He has no right to deprive future generations of a past that belongs to our collective memory. To forget would be not only dangerous but offensive; to forget the dead would be akin to killing them a second time. The witness has forced himself to testify. For the youth of today, for the children who will be born tomorrow. He does not want his past to become their future." Elie Wiesel, Night, Preface to the New Translation (New York: Hill and Wang, c2006), page xv.
He was capable of being so kind to the children, to have them become fond of him, to bring them sugar, to think of small details in their daily lives, and to do things we would genuinely admire ... And then, next to that, ... the crematoria smoke, and these children, tomorrow or in a half-hour, he is going to send them there. Well, that is where the anomaly lay.[48]