Summary Why was nuclear fission discovered under the repressive conditions of the Third Reich and not in one of the other leading countries in science? The attempts to answer this question leads to the formulation of the hypothesis that under the very special constellation of the working relations between Hahn and Meitner, the forced emigration of Meitner was advantageous insofar as it emancipated Hahn from the physical guardianship of Meitner, and liberated his chemical competence. This was a prerequisite to recognizing (...) the presence of Barium in the debris of Uranium decay. At the same time it liberated Meitner so that she could break with the old physicalconcepts of knowledge when accepting Hahn's chemical results, and find the correct interpretation of the experiment. Moreover, Hahn's and Strassmann's inner emigration which kept them away from participating in political activities and engagements, as well as their abstinence from competing in fashionable research (which was stimulated by the increasing political isolation of Germany) helped them to concentrate on their more restricted investigations following unfashionable lines of thinking and were among the favourable conditions for making their great discovery. (shrink)