Darkness had closed over the tents of the Macedonians, when Alexander's veteran general, Parmenio, came to him, and proposed that they should make a night attack on the Persians. The King is said to have answered, that he scorned to such a victory, and that Alexander must conquer openly and fairly. Arrian justly remarks that Alexander's resolution was as wise as it was spirited. Besides the confusion and uncertainty which are inseparable from night engagements, the value of Alexander's victory would have been impaired, if gained under circumstances which might supply the enemy with any excuse for his defeat, and encourage him to renew the contest. It was necessary for Alexander not only to beat Darius, but to gain such a victory as should leave his rival without apology for defeat, and without hope of recovery.
The Persians, in fact, expected, and were prepared to meet a night attack. Such was the apprehension that Darius entertained of it, that he formed his troops at evening in order of battle, and kept them under arms all night. The effect of this was, that the morning found them jaded and dispirited, while it brought their adversaries all fresh and vigorous against them.
The written order of battle which Darius himself caused to be drawn up, fell into the hands of the Macedonians after the engagement, and Aristobulus copied it into his journal. We thus possess, through Arrian, unusually authentic information as to the composition and arrangement of the Persian army. On the extreme left were the Bactrian, Daan, and Arachosian cavalry. Next to these Darius placed the troops from Persia proper, both horse and foot. Then came the Susians, and next to these the Cadusians. These forces made up the left wing. Darius's own station was in the centre. This was composed of the Indians, the Carians, the Mardian archers, and the division of Persians who were distinguished by the golden apples that formed knobs of their spears. Here also were stationed the body-guard of the Persian nobility. Besides these, there were in the centre, formed in deep order, the Uxian and Babylonian troops, and the soldiers from the Red Sea. The brigade of Greek mercenaries, whom Darius had in his service, and who were alone considered fit to stand in the charge of the Macedonian phalanx, was drawn up on either side of the royal chariot. The right wing was composed of the Coelosyrians and Mesopotamians, the Medes, the Parthians, the Sacians, the Tapurians, Hyrcanians, Albanians, and Sacesinae. In advance of the line on the left wing were placed the Scythian cavalry, with a thousand of the Bactrian horse, and a hundred scythe-armed chariots. The elephants and fifty scythe-armed chariots were ranged in front of the centre; and fifty more chariots, with the Armenian and Cappadocian cavalry, were drawn up in advance of the right wing.
Thus arrayed, the great host of King Darius passed the night, that to many thousands of them was the last of their existence. The morning of the first of October, two thousand one hundred and eighty-two years ago, dawned slowly to their wearied watching, and they could hear the note of the Macedonian trumpet sounding to arms, and could see King Alexander's forces descend from their tents on the heights, and form in order of battle on the plain. [See Clinton's "Fasti Hellenici." The battle was fought eleven days after an eclipse of the moon, which gives the means of fixing the precise date.]
There was deep need of skill, as well as of valour, on Alexander's side; and few battle-fields have witnessed more consummate generalship than was now displayed by the Macedonian king. There were no natural barriers by which he could protect his flanks; and not only was he certain to be overlapped on either wing by the vast lines of the Persian army, but there was imminent risk of their circling round him and charging him in the rear, while he advanced against their centre. He formed, therefore, a second or reserve line, which was to wheel round, if required, or to detach troops to either flank; as the enemy's movements might necessitate: and thus, with their whole army ready at any moment to be thrown into one vast hollow square, the Macedonians advanced in two lines against the enemy, Alexander himself leading on the right wing, and the renowned phalanx forming the centre, while Parmenio commanded on the left.
Such was the general nature of the disposition which Alexander made of his army. But we have in Arrian the details of the position of each brigade and regiment; and as we know that these details were taken from the journals of Macedonian generals, it is interesting to examine them, and to read the names and stations of King Alexander's generals and colonels in this the greatest of his battles.
The eight troops of the royal horse-guards formed the right of Alexander's line. Their captains were Cleitus (whose regiment was on the extreme right, the post of peculiar danger), Graucias, Ariston, Sopolis, Heracleides, Demetrias, Meleager, and Hegelochus. Philotas was general of the whole division. Then came the shield-bearing infantry: Nicanor was their general. Then came the phalanx, in six brigades. Coenus's brigade was on the right, and nearest to the shield-bearers; next to this stood the brigade of Perdiccas, then Meleager's, then Polysperchon's; and then the brigade of Amynias, but which was now commanded by Simmias, as Amynias had been sent to Macedonia to levy recruits. Then came the infantry of the left wing, under the command of Craterus. Next to Craterus's infantry were placed the cavalry regiments of the allies, with Eriguius for their general. The Messalian cavalry, commanded by Philippus, were next, and held the extreme left of the whole army. The whole left wing was entrusted to the command of Parmenio, who had round his person the Pharsalian troop of cavalry, which was the strongest and best amid all the Thessalian horse-regiments.
The centre of the second line was occupied by a body of phalangite infantry, formed of companies, which were drafted for this purpose from each of the brigades of their phalanx. The officers in command of this corps were ordered to be ready to face about, if the enemy should succeed in gaining the rear of the army. On the right of this reserve of infantry, in the second line, and behind the royal horse-guards, Alexander placed half the Agrian light-armed infantry under Attalus, and with them Brison's body of Macedonian archers, and Cleander's regiment of foot. He also placed in this part of his army Menidas's squadron of cavalry, and Aretes's and Ariston's light horse. Menidas was ordered to watch if the enemy's cavalry tried to turn the flank, and if they did so, to charge them before they wheeled completely round, and so take them in flank themselves. A similar force was arranged on the left of the second line for the same purpose, The Thracian infantry of Sitalces was placed there, and Coeranus's regiment of the cavalry of the Greek allies, and Agathon's troops of the Odrysian irregular horse. The extreme left of the second line in this quarter was held by Andromachus's cavalry. A division of Thracian infantry was left in guard of the camp. In advance of the right wing and centre was scattered a number of light-armed troops, of javelin-men and bowmen, with the intention of warding off the charge of the armed chariots. [Kleber's arrangement of his troops at the battle of Heliopolis, where, with ten thousand Europeans, he had to encounter eighty thousand Asiatics in an open plain, is worth comparing with Alexander's tactics at Arbela. See Thiers's "Histoire du Consulat," &c. vol. ii. livre v.]
Conspicuous by the brilliancy of his armour, and by the chosen band of officers who were round his person, Alexander took his own station, as his custom was, in the right wing, at the head of his cavalry: and when all the arrangements for the battle were complete, and his generals were fully instructed how to act in each probable emergency, he began to lead his men towards the enemy.
It was ever his custom to expose his life freely in battle, and to emulate the personal prowess of his great ancestor, Achilles. Perhaps in the bold enterprise of conquering Persia, it was politic for Alexander to raise his army's daring to the utmost by the example of his own heroic valour: and, in his subsequent campaigns, the love of the excitement, of "the rapture of the strife," may have made him, like Murat, continue from choice a custom which he commenced from duty. But he never suffered the ardour of the soldier to make him lose the coolness of the general; and at Arbela, in particular, he showed that he could act up to his favourite Homeric maxim.