The great general staff began in 1883 to publish a series of historical monographs, of which the object is, in the case of subjects chosen from recent campaigns, "to throw light upon important questions relating to the art of command, in particular the mode of employing, and the performance possible to, the several arms; the service of security; minor warfare; fortification; the composition and preservation of armies." Those of the essays which take their subjects from earlier campaigns are intended "to enrich our insight into the nature of war, and to make possible a profounder and more correct judgment of events, and of the persons concerned in them." The _Order of Teaching_ of the War Academy describes the purpose of all these studies in military history. They are to lead to a knowledge of "the unchanging conditions upon which good generalship depends, in their connection with changing tactical forms." Before there can be good practice there must be a true theory, and a true theory can be acquired only from historical study pursued according to a sound method. Moreover, the theory can never have an independent existence; it must always derive its sustenance from fresh contact with the historical reality of which it is the abstract. It is like the giant Antasus, whose strength fails whenever he is lifted up from the touch of his mother Earth. On the other hand, historical study which did not yield a theory would be barren and useless. This connection between history and theory finds expression in the tradition of the Prussian service. The general staff has been no less active in the production of theoretical works than in that of historical studies. But in the department of theory each work is published on the responsibility of its author. There is no official theory;[6] only the theories of individual officers. A short account of the principal works which in this way emanated from the general staff during the reign of King William I. will show that the accepted body of military doctrine is almost entirely due to this one source.