=83.= The Macedonian phalanx, which formed the center of Alexander’s army, was the most effective body of heavy-armed troops known to ancient tactics. The men were placed sixteen deep, armed with the _sarissa_, or long pike, twenty-four feet in length. When set for action, the spear-heads of the first six ranks projected from the front. In receiving a charge, the shield of each man, held over the head with the left arm, overlapped that of his neighbor; so that the entire body resembled a monster clothed in the shell of a tortoise and the bristles of a porcupine. So long as it held together, the phalanx was invincible. Whether it advanced its vast weight upon an enemy like a solid wall of steel bristling with spear-points, or, kneeling, with each pike planted in the ground, awaited the attack, few dared to encounter it.
=84.= BATTLE OF ARBELA. On the morning of the 1st of October, B. C. 331, the two great forces met upon the plain of Gaugame´la. Alexander fought at the head of his cavalry, on the right of his army. Darius, in the Persian center, animated his men both by word and example. Both sides fought with wonderful bravery, but the perfect discipline of the Macedonians gained at length a complete victory. The Persian war-chariots, which, with long scythes extending from their wheels, were intended to make great havoc among the Greek horse, were rendered useless by a detachment of light-armed troops trained for the purpose, who, first wounding horses and drivers with their javelins, ran beside the horses and cut the traces or seized the reins, while the few which reached the Macedonian front were allowed to pass between files which opened to receive them, and were easily captured in the rear. Five brigades of the phalanx bore down the Greek mercenaries who were opposed to them, and penetrated to the Persian center, where Darius commanded in person. The king’s charioteer was killed by a javelin; he himself mounted a fleet horse and galloped from the field.
Elsewhere the issue of the day was much more doubtful for Alexander; but the news of Darius’s flight disheartened his officers, and spurred the Macedonians, who were outnumbered and almost overpowered, to fresh exertions. A party of Persian and Indian horsemen, who were plundering the Macedonian camp, were put to flight by a reserve corps of the phalanx. The fugitive king, followed at length by his whole army, directed his course to the city of Arbe´la, twenty miles distant, where his military treasures were deposited. The river Ly´cus lay in their way, crossed only by a narrow bridge, and the number of Persians drowned in this rapid stream exceeded even those who had perished upon the battle-field.