Ἀλεξάνδρου ἀνάβασις 5.16.1

5.16.1

αὕτη μὲν ἡ Πώρου τάξις ἦν. Ἀλέξανδρος δὲ ὡς ἤδη καθεώρα τοὺς Ἰνδοὺς ἐκτασσομένους, ἐπέστησε τοὺς ἱππέας τοῦ πρόσω, ὡς ἀναλαμβάνειν τῶν πεζῶν τοὺς ἀεὶ προσάγοντας. ὡς δὲ καὶ ἡ φάλαγξ αὐτῷ δρόμῳ συνάψασα ὁμοῦ ἤδη ἦν, ὁ δὲ οὐκ εὐθὺς ἐκτάξας ἐπῆγεν, ὡς μὴ καματηρούς τε καὶ πνευστιῶντας ἀκμῆσι παραδοῦναι τοῖς βαρβάροις, ἀλλὰ ἐς κύκλους παριππεύων ἀνέπαυε τοὺς πεζοὺς ἔστε καταστῆναι αὐτοῖς τὸν θυμόν.

In this manner had Poros arranged his troops. As soon as Alexander perceived that the Indians had been drawn up in battle order he made his cavalry halt, that he might get in hand each regiment of the infantry as it came up ; and even when the phalanx by a rapid march had effected a junction with the cavalry he still did not at once marshal its ranks and lead it into action, and thus expose the men, while tired and out of breath, to the barbarians, who were quite fresh, but he gave them time, while he rode round their ranks, to rest until they could recover themselves. When he had observed how the Indians were arranged he made up his mind not to advance against the centre, in front of which the elephants had been posted, while the intervals between them had been filled with compact masses of infantry, for he feared lest Poros should reap the advantage which he had calculated on deriving from that arrangement. But as he was superior in cavalry he took the greater part of that force, and marched along towards the left wing of the enemy to make his attack in this quarter. Koinos he sent at the head of his own regiment of horse and that of Demetrios to the right, and ordered him, when the barbarians on seeing what a dense mass of cavalry was opposed to them, should be riding along to encounter it, to hang close upon their rear. The command of the phalanx of infantry he committed to Seleukos, Antigenes, and Tauron, who received orders not to take part in the action till they saw that the phalanx of infantry and the cavalry of the enemy were thrown into disorder by the cavalry under his own command.
When the Indians were now within reach of his missiles he despatched against their left wing the horse archers, who were 1000 strong, to throw the enemy in that part of the field into confusion with storms of arrows and charges of their horses. He marched rapidly forward himself with the companion cavalry against the left wing of the barbarians, making haste to attack their cavalry in a state of disorder while they were still in column, and before they could deploy into line.