During the First World War, both antiaircraft defense and tide prediction became imperative for Britain. These required lengthy calculations by human “computers.” One such computer, Arthur Thomas Doodson, became prominent in both antiaircraft ballistics and tide calculations. This article examines the mathematical practices Doodson employed and, through analysis of his financial backers, why the calculations were carried out. Doodson utilized new calculation practices both to increase the complexity and amount of computations that could be carried out and to argue for further funding. Historians of science, including mathematics, can benefit from simultaneous analysis of both the practices and the patronage of scientists.