The killing grounds at Ponar are today part of a memorial site run by the Vilna Gaon Museum, in Vilnius. There is a granite obelisk inscribed with the date of the Soviet liberation of the region, and clusters of candles smoldering in the small shrines on the edge of the burial pits, in honor of the tens of thousands who perished here. A small museum near the entrance to the site collects photographs and testimonies from the camp. One enters the museum prepared to weep, and leaves insensate: The black-and-white images of tangled human limbs in a ditch, the crumpled corpses of children, the disinterred dead piled in wheelbarrows, waiting to be brought to the pyres—the effect of the material is deeply physical and hard to shake.
However, the route to a professorship was interrupted in 1938-1939 when he began his military experience by serving six months with a specially trained mountain light-infantry regiment. In 1940 he was placed in the reserve medical corps, following which he served three years with a Waffen SS unit. It was during this time period he was wounded and declared medically unfit for combat. Because he had acquitted himself brilliantly in the face of the enemy during the Eastern Campaign, he was promoted to the rank of captain.
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.
Dr. Mengele was nicknamed the "Angel of Death" by the prisoners because he had the face of an angel, yet he callously made selections for the gas chambers at Birkenau. He was nice to the children in the camp, yet he experimented on them as though they were laboratory rats. He volunteered to do the selections at Birkenau, even when it wasn't his turn, because he wanted to find subjects for his medical research on genetic conditions and hereditary diseases, which he had already begun before the war. He particularly wanted to find twins for the research that he had started before he was posted to Birkenau.
Irena Adamowicz Gino Bartali Archbishop Damaskinos Odoardo Focherini Francis Foley Marianne Golz Jane Haining Helen of Greece and Denmark Feng-Shan Ho Wilm Hosenfeld Constantin Karadja Jan Karski Valdemar Langlet Carl Lutz Aristides de Sousa Mendes Tadeusz Pankiewicz Giorgio Perlasca Marion Pritchard Ángel Sanz Briz Oskar Schindler Anton Schmid Irena Sendler Klymentiy Sheptytsky Ona Šimaitė Henryk Sławik Tina Strobos Chiune Sugihara Casper ten Boom Corrie ten Boom Johan van Hulst Raimondo Viale Raoul Wallenberg Johan Hendrik Weidner Rudolf Weigl Jan Zwartendijk

From 1933 until 1938, most of the people held in concentration camps were political prisoners and people the Nazis labeled as "asocial." These included the disabled, the homeless, and the mentally ill. After Kristallnacht in 1938, the persecution of Jews became more organized. This led to the exponential increase in the number of Jews sent to concentration camps.

Today, I am going to refer quite frankly to a very grave chapter. We can mention it now among ourselves quite openly and yet we shall never talk about it in public. I'm referring to the evacuation of the Jews, the extermination of the Jewish people. Most of you will know what it's like to see 100 corpses side by side or 500 corpses or 1,000 of them. To have coped with this and—except for cases of human weakness—to have remained decent, that has made us tough. This is an unwritten—never to be written—and yet glorious page in our history.[127]
These three extermination factories — with Belzec responsible for about 600,000 victims, Sobibor 200,000, Treblinka 900,000 — shared certain features. Like Auschwitz at a later stage, they were equipped with railroad terminals that the trains entered in reverse. The victims were ordered to undress and then led through a corridor to the gas chambers; the gas was composed of carbon monoxide produced by diesel motors. At first, the corpses were buried in mass graves, later they were burnt in crematoria. The similarity to the “euthanasia” program was evident here too. In August 1941, the camps inspector was SS Sturmbannfiihrer Christian Wirth who, like dozens of other specialists of “Operation T4,” was placed under Odilo Globocnik, the commander of the SS for the region of Lublin.
Nolte's views were widely denounced. The debate between the "specifists" and "universalists" was acrimonious; the former feared debasement of the Holocaust and the latter considered it immoral to hold the Holocaust as beyond compare.[478] In her book Denying the Holocaust (1993), Deborah Lipstadt viewed Nolte's position as a form of Holocaust denial, or at least "the same triumph of ideology over truth".[479] Addressing Nolte's argument, Eberhard Jäckel wrote in Die Zeit in September 1986 that "never before had a state, with the authority of its leader, decided and announced that a specific group of humans, including the elderly, women, children and infants, would be killed as quickly as possible, then carried out this resolution using every possible means of state power".[h] Despite the criticism of Nolte, Dan Stone wrote in 2010 that the Historikerstreit put "the question of comparison" on the agenda.[480] He argued that the idea of the Holocaust as unique has been overtaken by attempts to place it within the context of early-20th-century Stalinism, ethnic cleansing, and the Nazis' intentions for post-war "demographic reordering", particularly the Generalplan Ost, the plan to kill tens of millions of Slavs to create living space for Germans.[481] The specifist position continued nevertheless to inform the views of many specialists. Richard J. Evans argued in 2015:

Hilberg, Raul (1985). The Destruction of the European Jews: The Revised and Definitive Edition. New York: Holmes and Meier. ISBN 0-8419-0832-X – via search inside. The deportations ... were the work of a much larger apparatus that had to deal with a host of constraints and requirements. The effort, as we shall see, was deemed necessary to accomplish the Final Solution on a European-wide scale.[p.273] 

^ Jump up to: a b c Adolf Eichmann; Bet ha-mishpaṭ ha-meḥozi; Miśrad ha-mishpaṭim (1992). The trial of Adolf Eichmann: record of proceedings in the District Court of Jerusalem. Trust for the Publication of the Proceedings of the Eichmann Trial, in co-operation with the Israel State Archives, and Yad Vashem. pp. 522, 93. ISBN 0317058401. Volume 1. Also in: Timothy Snyder; Ray Brandon (2014). Stalin and Europe: Imitation and Domination, 1928–1953. Oxford University Press. p. 194. ISBN 0199945578. Quoted 15,000 dead at Dnipropetrovsk and 12,000 Jews murdered in Kharkiv.
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]