Ever since those days, for more than twenty centuries, the history of war on land has been the history of a struggle for pre-eminence between horsemen and footmen. The rivalry has been complicated by the invention of Artillery, and of late years by the development of fighting in the air; but it has gone on unceasingly, and can hardly be said to have come to an end even now. In the course of it there has often been a tendency to lose sight of the fact that combined effort for one purpose by all arms, and not rivalry between them, is the secret of success in war. But the long dispute and its vicissitudes form an interesting study. By the Romans the effective use of Cavalry was for a long time not well understood. Though they had their “Equites” from early days, they got to rely more and more for serious fighting upon their wonderful legions, and it was not until the Punic Wars that they learned their lesson. Hannibal, like Alexander, was a born leader of horse, and when a hundred years after Alexander’s death he invaded Italy by way of the Alps, he at once taught Western Europe what Alexander had taught the Greeks and Persians, that in the existing condition of military armament, Cavalry well trained and boldly used in masses could do great things on the battlefield. The successive victories which he gained in Italy, with very inferior numbers, over the proud and confident troops of Rome, were due in large measure to his skilful use of his horsemen. At Cannæ, for example, his wild Numidian light horse, riding without saddle or reins, and his heavier squadrons from Spain and the North, began by driving off the weak Roman Cavalry opposed to them, and then, wheeling inwards upon the rear of the advancing legions, enclosed them in a circle of steel from which there was no escape. Fifty thousand of them are said to have fallen, and for a time Rome seemed to be, perhaps really was, at his mercy. Every one knows the story of his long struggle against hopeless odds, and of his final defeat. When at last he was conquered the superiority in horsemen had passed to the Romans, and he was overwhelmed and crushed by his own methods. He had taught his enemies to fight.[1] As time went on they forgot in a measure the lesson they had learnt from him, and they suffered some heavy reverses in consequence--for example, in their wars with the Parthians which stopped their expansion eastward; but happily such enemies were rare, and gradually the legions won for Rome the empire of the Western world. It lasted as long as the spirit and discipline of their incomparable Infantry remained unimpaired.