With the appointment of Ludwig Prandtl as Professor of Applied Mechanics in 1904, the small university town of Göttingen became the cradle of modern fluid mechanics and aerodynamics. Prandtl not only founded two world-class research institutions here, the Aerodynamische Versuchsanstalt (AVA) and the Kaiser-Wilhelm-Institut für Strömungsforschung, but also the so-called "Göttingen School", an exceptionally fruitful scientific way of thinking characterised by a particular balance of physical intuition and mathematical exactitude. The scientific method of Prandtl and his students has found expression in numerous dissertations, monographs and textbooks, which are now regarded as classics and thus form part of the basic stock of fluid mechanics. However, many of these publications have not been available for a long time. The series "Göttinger Klassiker der Strömungsmechanik" therefore makes selected publications available again that can be attributed to the Göttingen school around Ludwig Prandtl or have a certain historical connection to it. The present volume is a speciality in that it does not deal with a scientific subject, but with a little-known subject from the history of science, which nevertheless has a close connection to the way of thinking and the leitmotifs of the Göttingen School around Ludwig Prandtl. The view was always firmly held that research institutions should have a high degree of autonomy and should not be overly restricted in their freedom by political or economic guidelines. In addition, collegial collaboration with aerodynamicists from other European countries such as France, England and the Netherlands was given exceptionally high priority in Göttingen from the very beginning. During the Second World War, these noble views were to be put to a serious test in a completely unexpected way when the Aerodynamische Versuchsanstalt (AVA) was entrusted with the supervision of several aeronautical research institutes in the occupied countries of Western Europe in order to utilise them for the German war effort. One of these institutions was the Nationaal Luchtvaartlaboratorium (NLL) in Amsterdam, which now came under "Göttingen's wing". This book tells the exciting story of how the German scientists, who had suddenly been transformed from colleagues into all-powerful occupiers, and the Dutch researchers, who were forced to co-operate, dealt with their responsibilities in this extreme situation.