2. =Applied tactics=[20] deals with the combined action of the several arms on the march, in camp, and in action, taking into account influences of the terrain, seasons, and the time of day in field warfare. Fortress warfare should, strictly speaking, be included under this heading; that is to say, the employment of tactical principles[21] pertaining to the mobile arms, in conjunction with foot-artillery and technical troops on a prepared battlefield. The principles are the same in field and fortress warfare; the only difference between them lies in the employment of the means necessitated by the preparation of a field of battle in time of peace. Military history shows that a clear distinction between field and fortress warfare is impossible. (Sebastopol, Düppel, Plevna, and Port Arthur). [20] V. BOGUSLAWSKI, _Entwickelung der Taktik_, II, Chapter 23. “The higher, Grand Tactics, is the Initiation and conduct of battles--subordinate, or minor tactics, is the manner of fighting, or the battle-tactics of an arm considered in its details.” [21] MAJOR GUNDELACH, _Exerzierreglement und Festungskrieg_, Berlin, 1908. 4. DRILL REGULATIONS. Drill regulations are the accumulation of the tactical views and lessons of a certain period. They illustrate the tactical condition which becomes perceptible at the moment of a certain development of the fighting tools as represented by man and weapons. Man, in his peculiarities, in his weaknesses, is the constant. He constitutes the psychological element, inseparable from the science of combat, and as such is the definitely given magnitude; the effect of weapons, however, appears always as the variable factor. New weapons, therefore, necessitate new tactics. It will be observed also “that changes of tactics have not only taken place _after_ changes in weapons, which necessarily is the case, but that the interval between such changes has been unduly long. This doubtless arises from the fact that an improvement of weapons is due to the energy of one or two men, while changes in tactics have to overcome the inertia of a conservative class; but it is a great evil. It can be remedied only by a candid recognition of each change.”[22] The history of the tactics of the 19th Century furnishes more than one instructive example of the magnitude of such “obstinate conservatism.” [22] MAHAN, _The Influence of Sea Power upon History_, pp. 9 and 10.