Besides the phalanx, Alexander had a considerable force of infantry who were called shield-bearers: they were not so heavily armed as the phalangites, or as was the case with the Greek regular infantry in general; but they were equipped for close fight, as well as for skirmishing, and were far superior to the ordinary irregular troops of Greek warfare. They were about six thousand strong. Besides these, he had several bodies of Greek regular infantry; and he had archers, slingers, and javelin-men, who fought also with broadsword and target. These were principally supplied to him by the highlanders of Illyria and Thracia. The main strength of his cavalry consisted in two chosen corps of cuirassiers, one Macedonian, and one Thessalian each of which was about fifteen hundred strong. They were provided with long lances and heavy swords, and horse as well as man was fully equipped with defensive armour. Other regiments of regular cavalry were less heavily armed, and there were several bodies of light horsemen, whom Alexander's conquests in Egypt and Syria had enabled him to mount superbly. A little before the end of August, Alexander crossed the Euphrates at Thapsacus, a small corps of Persian cavalry under Mazaeus retiring before him. Alexander was too prudent to march down through the Mesopotamian deserts, and continued to advance eastward with the intention of passing the Tigris, and then, if he was unable to find Darius and bring him to action, of marching southward on the left side of that river along the skirts of a mountainous district where his men would suffer less from heat and thirst, and where provisions would be more abundant. Darius, finding that his adversary was not to be enticed into the march through Mesopotamia against his capital, determined to remain on the battle-ground which he had chosen on the left of the Tigris; where, if his enemy met a defeat or a check, the destruction of the invaders would be certain with two such rivers as the Euphrates and the Tigris in their rear. The Persian king availed himself to the utmost of every advantage in his power. He caused a large space of ground to be carefully levelled for the operation of his scythe-armed chariots; and he deposited his military stores in the strong town of Arbela, about twenty miles in his rear. The rhetoricians of after ages have loved to describe Darius Codomannus as a second Xerxes in ostentation and imbecility; but a fair examination of his generalship in this his last campaign, shows that he was worthy of bearing the same name as his great predecessor, the royal son of Hystaspes.