As early as the eighteenth century, successful efforts were made to prevent, by means of energetic measures, the reappearance of plague in Europe; the Russo-Turkish War of 1828–9 was the last war in which it broke out. On the other hand, typhus fever continued to be the Nemesis of belligerent armies, while a new infectious disease, cholera, entered upon the scene and played a very important rôle in the Crimean War, and a by no means minor rôle in the war of 1866. Along with these diseases, typhoid fever advanced into the foreground about the middle of the last century, and it soon turned out to be one of the most dangerous diseases that occur among soldiers. This appearance of typhoid fever has led some to think that the disease has prevailed extensively only in comparatively recent times. Hirsch, however, ably defends the opposite view; he maintains that typhoid fever was in many instances confused with the _febres pestilentes_, _malignae_, _putridae_, and _nervosae_, with the mucous fevers, bilious fevers, putrid fevers, &c. In discussing the typhus-fever epidemics that occurred in the course of the Napoleonic wars, we have several times called attention to the fact that typhoid fever probably broke out in the form of epidemics; but it could be diagnosed with certainty only after post-mortem examinations began to be more frequent. At all events, typhoid fever is to-day prevalent all over the world, and there is always danger that field-armies will be infected with it, either in their own land or in the land of the enemy. All the wars of the last few decades have clearly demonstrated this fact. For a successful battle against war-pestilences, it is a fortunate coincidence that the civil as well as the military authorities are equally interested in their prevention. Every military leader knows how important it is for the soldiers to keep healthy, since their efficiency is otherwise seriously impaired. It is not our task to describe the particular measures that are to be adopted; the manuals of military sanitation give us accurate information regarding these matters. We merely mention the fact that it is of great value and importance to have physicians, who are well acquainted with hygienic problems, make a preliminary examination of sanitary conditions in the territory through which the soldiers will be required to pass in order to reach the scene of hostilities.