This plan, adapted as the basic tactical idea for 1919, had the war lasted, heralds the dawn of scientific military thought in its grasp of the truth that even the military objective is a moral one――the paralysis of the enemy’s command and not the bodies of the actual soldiers. “The wheel has come full circle,” for this blow at the hostile command was the method of Alexander, one of the greatest captains in all history――and who, unlike Napoleon, attained his ultimate political objective in its entirety. It was thus at Arbela that Alexander, with a small but highly trained force, manœuvred to strike through a gap at Darius, and with the flight of its chief the huge Persian army dissolved into a mob, its superior numbers but an encumbrance. THE EVOLUTION OF “NEW MODEL” ARMIES “Rome was not built in a day”――nor will be the armies of the “new model,” though, since the history of the material world is a tale of the replacement of the human muscles by machines, the end is inevitable. Civil developments in mechanical science have repeatedly and continuously influenced and changed the methods of warfare. The longbows of mediæval England had to give way to the musket, the “wooden walls” of Nelson’s time yielded to the ironclad, the sailing ship was replaced by the steamship. But natural conservatism and financial stringency make rapid changes in peace-time unlikely. Thus the first stage will probably be to provide infantry with mechanical legs to carry them to the battlefield, to replace horse-drawn artillery with motor-drawn, or motor-borne guns, and to develop the tank arm to the proportion that its tactical importance as the heir of cavalry demands. With their transport no longer tied to roads and railways, such armies could well make advances of a hundred miles in the day. A longer period must elapse before tanks swallow the older arms completely, though the absorption of these Jonahs will be hastened if the military leaders of the nations realize that the gas-weapon has come to stay, notwithstanding the paper decrees of Leagues and Conferences.