This paper studies the relationships between Douglas Hartree and Ralph Fowler’s work during World War I computing ballistics tables for the British military and their later investigations into atomic physics. Considering first their studies within the old quantum theory, and second their wave mechanical studies into the properties of atoms, the paper argues that these physicists took computational techniques developed and honed in the calculation of ballistic trajectories over into their later physics, and suggests that their approaches to atomic problems, as well as their outlooks on physics more generally, reveal subtle but important traces of their early computational efforts. More generally, the paper examines a pathway towards an early form of computational physics, one in which the requirements and limitations of computing helped guide physicists’ strategies in atomic theory.