In the 1980s, he was a principal protagonist in the Historians' Dispute (Historikerstreit) over how to incorporate Nazi Germany and the Holocaust into German historiography and over Hitler's intentions.

Born in Wesermünde, Hanover, Jäckel studied history at Göttingen, Tübingen, Freiburg, Gainesville, and Paris after World War II.

[1] After serving as an assistant and docent at Kiel until 1966, he taught from 1967 and followed Golo Mann as Professor for Modern History at the University of Stuttgart, a position that Jäckel retained until retirement in 1997.

[4] Jäckel has argued that Hitler felt there were three factors that determined a people's "racial value": its awareness of itself, the type of leadership that it had and its ability to make war.

[5] According to Jäckel, those for Germany meant ultranationalism, the Führerprinzip (Führer Principle) and militarism, and all three were the constants of Hitler's beliefs throughout his life.

[8] In Jäckel's view, Hitler in the Zweites Buch of 1928 established for the first time a logical link between his foreign policy conception and his antisemitism.

Jäckel attacked Irving for claiming that an entry in Heinrich Himmler's notebook saying "Jewish transport from Berlin, not to be liquidated", on 30 November 1941 proved that Hitler did not want to see the Holocaust happen.

[20] Jäckel used Hitler's "Prophecy Speech" of January 30, 1939 in which Hitler declared: I shall once again be your prophet: if international Jewry with its financial power in and outside of Europe should manage once more to draw the peoples of the world into world war, then the result will not be the Bolshevization of the world, and thus the victory of Jewry, but rather the total destruction of the Jewish race in Europe[21]Likewise, Jäckel used Himmler's Posen speeches of 1943 and certain other statements on his part in 1944 referring to an "order" from an unnamed higher authority as proof that Hitler had ordered the Holocaust.

[22] In the same way, Jäckel noted Hitler's order of 13 March 1941 for the Einsatzgruppen to be re-established for Operation Barbarossa as proof of the Führer's involvement in the Holocaust.

[23] Jäckel also argued that the entry in Joseph Goebbels's diary on 27 March 1942 mentioning the Führer's "Prophecy" was coming true was a sign that Hitler had ordered the Holocaust.

[26] Jäckel wrote that he had "easily" discovered the "lost" document in which the head of the Reich Chancellery, Hans Lammers, had written to Justice Minister Franz Schlegelberger that Hitler ordered him to put the "Jewish Question" on the "back burner" until after the war.

[31] Jäckel ended his essay that the "lost" document in no way proved that Hitler was unaware of the Holocaust and accused Irving of deceitfulness in claiming otherwise.

[37] Jäckel attacked Nolte's statement that Hitler had an especially-vivid fear of the Soviet "rat cage" torture by arguing that Hitler's statement of 1 February 1943 to his generals about captured German officers going off to the "rat cage" clearly meant the Lubyanka prison, and that was not, as Nolte argued, to be interpreted literally.

[40] Jäckel wrote in a 1986 essay, "The Impoverished Practice of Insinuation: The Singular Aspect of National-Socialist Crimes Cannot Be Denied", first published in the Die Zeit newspaper on September 12, 1986: Hitler often said why he wished to remove and kill the Jews.

On the contrary, Hitler was always convinced that Soviet Russia, precisely because it was ruled by Jews, was a defenseless colossus standing on clay feet.

[45] Against Nolte's claim that the Holocaust was not unique but rather one of out many genocides, Jäckel rejected Nolte's view and those of his supporters like Joachim Fest by writing: I, however claim (and not for the first time) that the National Socialist murder of the Jews was unique because never before had a nation with the authority of its leader decided and announced that it would kill off as completely as possible a particular group of humans, including old people, women, children and infants, and actually put this decision into practice, using all the means of governmental power at its disposal.

This idea is so apparent and so well known that it is quite astonishing that it could have escaped Fest's attention (the massacres of the Armenians in the Ottoman Empire during the First World War were, according to all we know, more like murderous deportations than planned genocide).

[54] The partnership with Lea Rosh begun in 1988 and led to a widely-watched four-part television documentary, Der Tod ist ein Meister aus Deutschland, a popular book of the same name and the Geschwister-Scholl-Preis in 1990.