In the late German Kaiserreich the invention and production of mathematical instruments became a particular strength of the German innovation system—this was part of a general development that made the German instrument industry the world leaders during this period of time. However, after WW I the financial crisis of the German state partly hindered the further development of large scale instruments, and as a consequence other national science systems partly overtook the world leading German science system. The case of the epoch-making Differential Analyzer built at MIT by the electrical engineer Vannevar Bush in 1931 serves not only to illustrate this argumentation, but it also shows that the ideology of pure science did not allow building a large scale analog computing machine in the environment of a German university. While some differential analysers were built in Britain and in Continental Europe in the 1930s, the German development started only after the outbreak of WW II, when the rationality of the German science system had changed totally to a rationality of applicability of science for military purposes. In 1939/40 two different ambitious differential analyzer projects were launched in connection with the Heereswaffenamt or rather with the V2 rocket project lead by Werner von Braun. The talk shows how the Third Reich used the scientific competence of mathematicians as resources for the developments of weapons in the military system and how, the other way round, mathematicians used the Third Reich to get financial and personnel resources for the building of differential analysers for their own purposes. Furthermore, it will be analysed, why all the differential analyser projects in the Third Reich failed in the end. The paper aims to focus on fundamental aspects of scientific and technological developments in computing in the Third Reich and to analyse the dynamics of its military-industrial-academic complex.