In countries which have the misfortune to be the scene of protracted wars, the mortality regularly undergoes a considerable increase. This is caused chiefly by the infectious diseases which in war times so often appear in the form of epidemics. These diseases, moreover, not only afflict the country in which the war is waged, but are also carried by prisoners, returning soldiers, and in other ways, into the land of the victor, where it is possible for them to spread over a large territory. A report on the loss of human life among that part of a population which does not participate in a war has not yet been undertaken, writings on war pestilences usually confining themselves to the losses within the armies themselves.[1] It is the purpose of the present study to investigate the losses sustained by the non-belligerent part of the population in consequence of epidemics caused by wars. In doing this it seems advisable to select a few war pestilences which on account of their enormous extent are particularly notable, and to subject them to an exhaustive discussion. This method has the advantage that it will enable us to show in individual cases how it is possible for these pestilences to extend over such a vast territory, under what circumstances they spread from place to place, and how they enter regions remote from the scene of war. For this exhaustive discussion the writer has chosen the pestilences that occurred during the Thirty Years’ War, the epidemic of typhus fever after Napoleon’s Russian Campaign, and the pandemic of small-pox after the Franco-German War of 1870–1. These epidemics afford very instructive examples of what horrible losses both friends and enemies may sustain in consequence of war pestilences. While the outbreaks of ‘plague’ in the course of the Thirty Years’ War have already been made the subject of a comprehensive account, strange to say there are no such accounts of the other two epidemics; to give a clear picture of these pestilences the writer was therefore constrained to collect the necessary information from widely dispersed sources. In gathering his material a number of large German libraries assisted him most kindly—particularly, the Royal National Library at Stuttgart and the University libraries of Strassburg and Tübingen. The other parts of the history of war pestilences are set forth in a more general way; for an exhaustive treatment of them would have necessitated several years of preliminary work, which the writer in the short time at his disposal was unable to undertake.