Ptolemy states further that Alexander at first despatched against the prince the horse archers, and led the cavalry himself, under the belief that Pôros was advancing against him with the whole of his army, and that this was a body of advanced cavalry thrown forward by Pôros. But when he discovered what the real strength of the Indians was he then briskly charged them with what cavalry he had with him. When they noticed that Alexander himself and his body of cavalry did not charge them in an extended line, but by squadrons, their ranks gave way, and 400 of their horsemen fell, and among them the son of Pôros. Their chariots, moreover, were captured, horses and all, for they proved heavy in the retreat and useless in the action itself, by having stuck fast in the clay. When the horsemen who had escaped from this rout reported one after another to Pôros that Alexander himself had crossed the river with the strongest division of his army, and that his son had been slain in the fight, he was still at a loss what to determine, for the division which had been left with Krateros in the great camp right opposite to his own position appeared to be undertaking the passage, but he at last decided to march with all his forces against Alexander and fight it out with the strongest division of the Macedonians led by the king in person. He nevertheless left there in his camp a few of the elephants and a small force to deter the cavalry under the command of Krateros from landing. He then took all his cavalry, 4000 strong, all his chariots, 300 in number, 200 of his elephants, and 30,000 efficient infantry, and marched against Alexander. When he found a place where he saw there was no clay, but that the ground from its sandy nature was all flat and firm, and suited for the movements of cavalry whether charging or falling back, he then drew up his army in order of battle,[104] posting his elephants in the front line at intervals of at least 100 feet, so as to have his elephants ranged in front before the whole body of his infantry, and so to spread terror at all points among Alexander’s cavalry. He took it for certain besides that none of the enemy would have the audacity to push in at the intervals between the elephants—not the cavalry, since their horses would be terrified by these animals, and much less the infantry, since they would be checked in front by his heavy-armed foot soldiers falling upon them, and trampled down when the elephants wheeled round upon them. Behind these he drew up his infantry, which did not close up in one line with the elephants, but formed a second line in their rear, so that the regiments were only partly pushed forward into the intervals. He had also troops of infantry posted on the wings beyond the elephants, and on both sides of the infantry the cavalry had been drawn up, and in front of it the chariots. _Chapter XVI.—The plan of attack adopted by Alexander_