of the SS, headed by Heinrich Himmler. In this, Heisenberg was called a "White Jew" who should be made to "disappear". These attacks were taken seriously, as Jews were violently attacked and incarcerated. Heisenberg fought back with an editorial and a letter to Himmler, in an attempt to resolve the matter and regain his honour. At one point, Heisenberg's mother visited Himmler's mother. The two women knew each other, as Heisenberg's maternal grandfather and Himmler's father were rectors and members of a Bavarian hiking club. Eventually, Himmler settled the Heisenberg affair by sending two letters, one to SS Gruppenführer Reinhard Heydrich and one to Heisenberg, both on 21 July 1938. In the letter to Heydrich, Himmler said Germany could not afford to lose or silence Heisenberg, as he would be useful for teaching a generation of scientists. To Heisenberg, Himmler said the letter came on recommendation of his family and he cautioned Heisenberg to make a distinction between professional physics research results and the personal and political attitudes of the involved scientists. Wilhelm Müller replaced Sommerfeld at the Ludwig Maximilian University of Munich. Müller was not a theoretical physicist, had not published in a physics journal, and was not a member of the German Physical Society. His appointment was considered a travesty and detrimental to educating theoretical physicists. The three investigators who led the SS investigation of Heisenberg had training in physics. Indeed, Heisenberg had participated in the doctoral examination of one of them at the Universität Leipzig. The most influential of the three was Johannes Juilfs. During their investigation, they became supporters of Heisenberg as well as his position against the ideological policies of the Deutsche Physik movement in theoretical physics and academia. German nuclear weapons program Pre-war work on physics In mid-1936, Heisenberg presented his theory of cosmic-ray showers in two papers. Four more papers appeared in the next two years. In December 1938, the German chemists Otto Hahn and Fritz Strassmann sent a manuscript to The Natural Sciences reporting they had detected the element barium after bombarding uranium with neutrons and Otto Hahn concluded a bursting of the uranium nucleus; simultaneously, Hahn communicated these results to his friend Lise Meitner, who had in July of that year fled to the Netherlands and then went to Sweden. Meitner, and her nephew Otto Robert Frisch, correctly interpreted Hahn's and Strassmann's results as being nuclear fission. Frisch confirmed this experimentally