He seemed instinctively to have taken in the significance of the enlarged scale on which warfare under him was conducted. He had to solve untried problems, due to the vast extent of territory he traversed, so different in every way from the restricted limits of continental Greece. The students of strategy have especially admired his originality in the systematic following up of a victory, an element in successful warfare not dreamed of by the citizen generals of Greece. In the Peloponnesian war it never occurred to the Spartans when they had defeated the Athenians to besiege Athens. But after Issus, a most decisive victory, Alexander showed the utmost resourcefulness in the long seven months’ siege of Tyre, and finally took it by storm. The same mobility of generalship is noted in India, where he did not hesitate in the face of a division of elephants, an unknown arm in warfare, to cross a river and deliver a frontal attack. The army, which never failed to respond to the ever-developing visions and schemes of its commander, until he had carried it to the eastern limits of the known world in his career of conquest, was at the very beginning of Alexander’s career trained for any military project he might propose. It was composed of seasoned officers and men, who had proved their mettle and gained their laurels under Philip while he was bringing his army to the highest pitch of excellence. In the list of great Greek military leaders, Philip is placed by the side of Epaminondas, the Theban, the man who revolutionized the Greek art of warfare by a fine stroke of genius. It had been noted that in the Greek battles, where the phalanx had become the controlling factor, its right wing was frequently victorious in both opposing armies. This phenomenon was simply due to the fact that the Greek heavy-armed soldier carried a shield on his left arm and naturally tended to move in an oblique direction towards the right hand. The chief innovations introduced by Epaminondas were the strengthening of the left wing by increasing its depth--it was made fifty men deep--and the holding back of the right wing as the whole phalanx advanced in battle array. With the increased depth of the phalanx, the front was necessarily shortened, and in order to prevent flanking operations, Epaminondas made great use of cavalry, in protecting the flanks of his men from an encircling movement on the part of the enemy, whose phalanx, since it was not so deep (being the old shape), would stretch out on both sides beyond the lines of the Theban line. As a general, Philip accepted these new tactical principles originated by Epaminondas, and applying them to Macedonian conditions, made of the Macedonian army a wonderfully effective military machine.