As regards the strictly military side of this work, though the recent researches of the French General Staff into the records and documents of the Napoleonic period have shown conclusively that Clausewitz had never grasped the essential point of the Great Emperor’s strategic method, yet it is admitted that he has completely fathomed the spirit which gave life to the form; and notwithstanding the variations in application which have resulted from the progress of invention in every field of national activity (not in the technical improvements in armament alone), this spirit still remains the essential factor in the whole matter. Indeed, if anything, modern appliances have intensified its importance, for though, with equal armaments on both sides, the form of battles must always remain the same, the facility and certainty of combination which better methods of communicating orders and intelligence have conferred upon the Commanders has rendered the control of great masses immeasurably more certain than it was in the past. Men kill each other at greater distances, it is true—but killing is a constant factor in all battles. The difference between “now and then” lies in this, that, thanks to the enormous increase in range (the essential feature in modern armaments), it is possible to concentrate by surprise, on any chosen spot, a man-killing power fully twentyfold greater than was conceivable in the days of Waterloo; and whereas in Napoleon’s time this concentration of man-killing power (which in his hands took the form of the great case-shot attack) depended almost entirely on the shape and condition of the ground, which might or might not be favourable, nowadays such concentration of fire-power is almost independent of the country altogether. Thus, at Waterloo, Napoleon was compelled to wait till the ground became firm enough for his guns to gallop over; nowadays every gun at his disposal, and five times that number had he possessed them, might have opened on any point in the British position he had selected, as soon as it became light enough to see. Or, to take a more modern instance, viz., the battle of St. Privat-Gravelotte, August 18, 1870, where the Germans were able to concentrate on both wings batteries of two hundred guns and upwards, it would have been practically impossible, owing to the section of the slopes of the French position, to carry out the old-fashioned case-shot attack at all. Nowadays there would be no difficulty in turning on the fire of two thousand guns on any point of the position, and switching this fire up and down the line like water from a fire-engine hose, if the occasion demanded such concentration. But these alterations in method make no difference in the truth of the picture of War which Clausewitz presents, with which every soldier, and above all every Leader, should be saturated.