Fifteen hundred years later the German army was, in turn, the traditional symbol of military power. For four years, her machine-gunners, heirs of the Roman legionaries, defied all the efforts of orthodox tactics to overthrow them. On the _8th of August, 1918_, the German infantry legions were overrun and slaughtered by the onset of the British tanks, almost as helplessly as their forerunners at Adrianople, exactly fifteen hundred and forty years before. Let the story be epitomized in the words of the enemy, of Ludendorf himself: “_August 8th was the black day of the German army in the history of the war._ The divisions in line allowed themselves to be completely overwhelmed. Divisional staffs were surprised in their headquarters by enemy tanks.” On the final phase of the war the verdict of Ludendorf was “mass attacks by tanks ... remained hereafter our most dangerous enemies.” The lesson to be drawn from this historical analogy is that the tank attack is the modern substitute for the cavalry charge, the supreme value of which lay in its speed and impetus of assault, and the demoralizing effect of its furious onset. The deadliness of modern fire-weapons brought about the extinction of the cavalry charge, and with its disappearance warfare became lopsided and stagnant. The stalemates of recent campaigns are to be traced to the lack of any means of delivering and exploiting a decisive blow. If, instead of regarding cavalry as men on horseback, soldiers thought of it as _the mobile arm_, the main cause of the interminable siege warfare of the Russo-Japanese and Great Wars would be apparent. The practical view of history lies in projecting the film of the past on the blank screen of the future. Once appreciate that tanks are not an extra arm or a mere aid to infantry but the modern form of heavy cavalry and their true military use is obvious――to be concentrated and used in as large masses as possible for a decisive blow against the Achilles’ heel of the enemy army, the communications and command centres which form its nerve system. Then not only may we see the rescue of mobility from the toils of trench-warfare, but with it the revival of generalship and the art of war, in contrast to its mere mechanics. Instead of machines threatening to become the master of men, as they actually did in 1914–18, they will give man back opportunities for the use of his art and brain, and on the battlefields of the future may be expected the triumphs of an Arbela, of quality over quantity. “It is the _Man_, not men, who count in war.” The tank assault of to-morrow is but the long-awaited re-birth of the cavalry charge, with the merely material changes that moving fire is added to shock, and that the armoured cavalry-tank replaces the vulnerable cavalry-horse. Thus, to paraphrase, “The cavalry is dead! Long live the cavalry!”