This article examines major epidemics of bacillary dysentery in the German army as well as among civilians in eastern Europe and in Germany during World War I. These epidemics were all the more surprising in light of prewar advances in understanding the disease and limiting dysentery outbreaks. Three major reasons are adduced for the incapacity of German military hygienists to prevent wartime epidemics. First was the difficulty of bacteriological testing at the front, especially early in the war, with negative consequences for diagnosis, therapy, and disease control. Second was inadequate hygiene including major shortcomings in latrine cleanliness and attempts to grapple with the "fly plague." Third was the lack of a Pasteur-type vaccine until late in the war. Susceptibility to dysentery was also heightened by war-related nutritional deficiencies. Taking off from an article by the English medical historian Roger Cooter, this article shows that the concept of "war dysentery" was socially constructed and served a variety of professional interests but at the same time takes issue with Cooter's arguments against linking "war" and "epidemics" pathogenetically.