THE SIZE OF THE ARMY
In Philip’s time the Macedonian forces had consisted of thirty thousand infantry and from three to four thousand horsemen. Alexander had led about the same number of troops against Thebes. On his departure for Asia he left twelve thousand foot-soldiers and fifteen hundred mounted men in Macedonia under the command of Antipater, and their place was taken by eighteen hundred Thessalian knights, five thousand Greek mercenaries, and seven thousand heavy-armed troops furnished by the Greek states. Besides these he had in his following five thousand Triballians, Odrysians, Illyrians, etc., from one to two thousand archers and Agrianian light infantry, Greek cavalry to the number of six hundred, Thracian and Pæonian to the number of nine hundred. The sum total of his troops therefore amounted to not much over 30,000 infantry and a little more than 5,000 horse. This, with slight divergencies suggested by the details of the narrative, is the estimate of Diodorus. Ptolemy Lagi gives the same figures in his Memorabilia, and Arrian repeats them after him. When Anaximenes reckons thirty-four thousand men on foot and five thousand five hundred on horseback he perhaps includes the corps which had already been despatched to Asia by Philip. The estimate of Callisthenes, 40,000 infantry, is obviously too high.
The whole body of infantry and cavalry was not divided into legions or brigades, but into troops bearing the same weapons and, to some extent, recruited from the same district. The very advantages of a Macedonian army rendered necessary an arrangement which would be unsatisfactory under present conditions; the phalanx would have been no phalanx if it had fought with cavalry, light infantry, and Thracian slingers all combined into a complete army in miniature. It is the general use of small fighting units which has made it necessary for the parts of an army to be self sufficient, and to repeat on a small scale the organisation of the whole. Against such an enemy as the Asiatic hordes—collected together for a pitched battle without previous discipline or training, giving up all for lost after a single defeat, and gaining nothing but renewed danger by a victory over organised troops—against such an enemy, solid and homogeneous masses have the advantage of simplicity, weight, and internal stability, and in the same region where Alexander’s phalanx overpowered the army of Darius the Roman legions succumbed to the vehement onslaught of the Parthians. On the whole, Alexander’s army was well adapted for such pitched battles, and hence the bulk of it consisted of his phalanxes and heavy cavalry.