the distances to be traversed and the mass of men and materials to be conveyed, never until the present War have such demands been made on the railways. The enormous numbers engaged in the War involved a very high degree of dependence on the railways. Even in 1870-71 the German second army (which at that time comprised only three army corps) experienced at the Loire the serious inconvenience of not having adequate railway communications in their rear. At the present day, the unhampered development of operations in the war of movement and a secure maintenance of positions in entrenched warfare are only possible if the bringing up of munitions, stores, and men, and the removal of the wounded, as well as the systematic organisation of the whole sanitary service, are ensured by means of the railways. Only from time to time has it been possible to dispense with them by having recourse to motor wagons; but the latter have never really furnished an adequate substitute for railways. Moreover, the notion that railways were not to be relied on as an instrument of war, because they could be so easily destroyed, has proved itself untenable. This was entirely applicable in the case of the destruction of railways in 1870, but present-day technology has always found means to remove such difficulties with comparative speed and to make the lines serviceable again. Where special difficulties presented themselves, as for instance in Macedonia in the late autumn of 1915, operations have been unavoidably brought to a standstill. In his history of the autumn campaign of 1813,[1] Lieutenant-General Friederich attributes the overthrow of Napoleon principally to the fact that the manipulation and the mutual reinforcement at the right moment of the various divisions in Saxony, Silesia, and the Mark, on the Lower Elbe and in Bavaria, of a French army numbering in all more than half a million men could only be possible with the aid of railways and the electric telegraph. The armies of that day had already outgrown the technical resources of their age. If we consider that, after Napoleon himself had returned to Dresden from the pursuit of the main army of the allies which began on the 28th of August, it was not until the 3d of September that he was fully informed of the defeats of Oudinot at Gross-Beeren and of Macdonald at the Katzbach with all their consequences, and was able to form a decision adapted to the circumstances, and this within a circuit of from thirty to sixty miles from Dresden, which was all the area that the disposition of his troops extended over at that time, we perceive the great obstacles which opposed themselves in those days to the joint direction of independent bodies of troops, even when the distance between these was comparatively insignificant.