Abstract Potential military applications of geology became apparent in Europe by the late eighteenth century, notably to Napoleon Bonaparte. In the United Kingdom, nineteenth-century practice was commonly to teach elementary geology to army officer cadets, and in twentieth-century conflicts to deploy a single uniformed geologist as a staff officer within each major regional headquarters, initially leaving terrain analysis to geographers. In Germany, considerably greater use was made of uniformed geologists serving as teams within all theaters of military operation in both world wars, generating a wealth of data now published or accessible in national archives. In the United States, a few military geologists were appointed to serve in uniform in France during World War I, but during World War II, a far greater number were civilians, based within a Military Geology Unit of the U.S. Geological Survey at Washington, D.C. Despite different organizational backgrounds, and irrespective of nationality, military geologists have addressed similar geoscience problems.