This thesis asks how the Great War affected physical science in Britain. It examines how graduate scientists and army officers worked together in the War, concentrating on the two fields of ballistics and chemical warfare. In these fields many previous accounts have discussed only the civilians. This study gives an outline of the various military institutions where soldiers in the technical corps (Artillery and Engineers) were trained, and where the state made, tested and stored arms. It argues that these corps had a characteristic technical culture, in which science was not studied for its own sake, but always with an end in view that would benefit the state: mathematics, astronomy and geodesy for survey, geology for public works, and so on. This was quite different from the professional values of pure science and mathematics. The thesis sees the effects of the War on science on two levels, the personal and the structural. Those engaged in war-work responded very variously: some had the directions of their interests greatly changed, so that the ballistics work accelerated the growth in numerical analysis; for others the War was simply an interruption, either a destructive one, or one that was rewarding but little related to the scientist’s academic career. Several of those who had done war-work maintained their links with the military for the rest of their lives. Structurally, the state increased its support for applied science with military applications, at the National Physical Laboratory, Famborough, Porton, and Woolwich. The scale of academic experiments, however, did not grow correspondingly after the War. After the War, the Army significantly increased its research activities (though constrained by limited budgets), and incorporated university teaching in the training of its engineering personnel, initially as a stop-gap, but then by choice.