I was more alluding to the fact that derivatives of his nerve agents were used to gas prisoners in concentration camps (Zyklon B)

From 1919 to 1923 Haber continued to be involved in Germany's secret development of chemical weapons, working with Hugo Stoltzenberg, and helping both Spain and Russia in the development of chemical gases.[12]: 169 

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During the 1920s, scientists working at Haber's institute developed the cyanide gas formulation Zyklon A

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By 1931, Haber was increasingly concerned about the rise of National Socialism in Germany, and the possible safety of his friends, associates, and family. Under the Law for the Restoration of the Professional Civil Service of 7 April 1933, Jewish scientists at the Kaiser Wilhelm Society were particularly targeted. The Zeitschrift für die gesamte Naturwissenschaft ("Journal for all natural sciences") charged that "The founding of the Kaiser Wilhelm Institutes in Dahlem was the prelude to an influx of Jews into the physical sciences. The directorship of the Kaiser Wilhelm Institute for Physical and Electrochemistry was given to the Jew, F. Haber, the nephew of the big-time Jewish profiteer Koppel". (Koppel was not actually related to Haber.)[12]: 277–280  Haber was stunned by these developments, since he assumed that his conversion to Christianity and his services to the state during World War I should have made him a German patriot. [39] Ordered to dismiss all Jewish personnel, Haber attempted to delay their departures long enough to find them somewhere to go.[12]: 285–286  As of 30 April 1933, Haber wrote to Bernhard Rust, the national and Prussian minister of Education, and to Max Planck, president of the Kaiser Wilhelm Society, to tender his resignation as the director of the Kaiser Wilhelm Institute, and as a professor at the university, effective 1 October 1933. He said that although as a converted Jew he might be legally entitled to remain in his position, he no longer wished to do so.[12]: 280