The military historian E. W. Marsden, concluding his analysis of the battle, puts down the victory partly to the Macedonians’ superior morale and closer ties with their commander, partly to Alexander’s remarkably detailed understanding of the art of war. He sums up,
It is difficult to re-create the chaos characteristic of full-scale engagements at certain stages, the confusion caused by noise, movement and dust, the atmosphere of doubt and uncertainty, the horrible carnage… It must be extraordinarily difficult for modern generals to remain calm and detached when controlling operations in a command-post some miles from the scene of the fighting. How much harder it would be for Alexander and Darius who were stationed in the line of battle itself! Darius appears not to have possessed that rare ability to sift conflicting reports, to make correct observations, and, remaining cool and unflurried, to issue swift and well-considered orders in such circumstances. Alexander had this ability in a pronounced degree. That was the third decisive factor at Gaugamela.
Darius and a ragged remnant struggled southeast over the mountain passes towards Ecbatana (Hamadan), the summer resort of the Persian kings. The Royal Road south, to Babylon, Susa and Persepolis, the rich heart of the empire, was left open to Alexander. The choice of objective did not take him long. By now he must have talked through his interpreters with captive Persians, and formed his own estimate of Darius’ value to morale.
Curtius, drawing again it seems on the Persian informant to whom some earlier chronicler had access, says that Darius abandoned the great cities to keep Alexander from following his trail. Certainly if his objective was to rally Persia to arms, his remaining months of life give little sign of it. Though his son was a captive, he had an effective heir in his warrior brother Oxathres. Had he succeeded a Great King fallen inspiringly in battle against the invader, the course of the war might have been much altered.
As it was, its next phase was mere swanning for Alexander. He may not yet have guessed it while nearing the huge brick-and-bitumen walls of Babylon. Herodotus, who went there a century before, says they enclosed 60 square miles, in which food crops could be grown during a siege. Even the old fortifications of Nebuchadnezzar, now an inner ring, were vast. The outer ones were 180 feet thick and 400 high, a monument to the Assyrian builders with their hordes of expendable slaves. Cyrus had taken it without a fight; but Alexander must have known Xenophon’s livelier version. Its mass was visible for miles across the plain, promising a siege at least as colossal as that of Tyre. But there was no need even to reconnoitre it. Alexander was met on the road by Mazaeus its satrap, fresh from his tussle with Parmenion. Now, bringing his children as hostages, he invited Alexander in.
It was not much more than a century since Babylon had last tried to revolt from Persia, and been crushed by Xerxes with severity. Its luxury-loving people were disaffected or indifferent; its garrison was disillusioned; its commander had no sentiment for a beaten fugitive king. It remained only to placate the victor. Alexander, naturally wary of a trap when this astonishing gift was offered him, still advanced in battle order, leading the van. But the walls were undefended, the hundred gates wide open, the drawbridges down. He entered as King of Babylon, in a state chariot plated with gold, among splendours never to be surpassed in the triumphs of the Caesars. The city treasurer, eager to outdo Mazaeus, had had the route strewn with flowers and censed with perfume. Rare and exotic gifts, choice horses, cars bearing caged lions and leopards, were led in the procession; magi and priests attended, royal praise singers chanted, Mazaeus’ cavalry paraded. As always with Alexander, one Roman adornment was lacking: the spectacle of captives humiliated in chains.
After viewing the ancient splendours of the palace, he visited its treasury. Of this vast hoard no assessment remains. He paid out lavish bounties to all his men; his mercenaries got two months’ extra pay. These included many Greeks who, given leave to go home when the Greek cities had all been fired, had chosen to stay on. All could now afford the luxuries of a city they had not been let loose to sack. Here in Babylon was the real beginning of his extravagant generosities which henceforth would flow out to all around him. This first donative was good policy and fair dealing. But to give pleasure, to be surrounded with gratitude and liking, met a deep need in his nature. In his childhood, his tutor Leonidas had made him live poor in the midst of plenty; he loved profusion as only those can who have been pinched. He loved display; it went with his sense of theatre. All these cravings were fed in Babylon; as the money came in, he would develop his personal style.
From the throne he granted Babylon the status it had had before Xerxes crushed it and threw down the ziggurat of Bel. The priests of the god were now given much gold to rebuild his sanctuary. (It would have fateful consequences later.) Mazaeus was at once confirmed in his rank of satrap. The gift of this great office to a Persian, gratifying to Iranians, can hardly have been as popular with Macedonians; to emphasize his good performance at Gaugamela would be natural, and Parmenion’s reputation could not be damaged by tributes to the strength of his opponent. The posts of garrison commander and treasurer of course went to Macedonians. Alexander was a month in Babylon, giving his men a holiday. He was busy himself, though it is not likely that the pomps of the court were irksome. When ready to march, he put his now impressive treasure train in the charge of Harpalus; the loyal friend of boyhood was to know himself thoroughly forgiven.
The soldiers were broken intently after the demoralizing joys of the city; marched into pleasant country where games were held. There was an important novelty: prizes were offered for valour on campaign. Typically of the extraordinary rapport between this army and its leader, all ranks were invited to offer the judges their views by acclamation. There were eight awards. They consisted not of the usual gold wreath or money but of command appointments, each over a thousand men. Up till now Alexander had kept his staff within the tribal hierarchies of the home land; now, with sound dramatic flair and canny assurance that choices would be popular, he introduced real promotion on merit.
Susa lay ahead, but required no haste. It had capitulated directly after the battle to the envoys he had sent ahead. News of Darius’ flight would have outstripped them, for the Royal Road had the world’s fastest post relay, with fresh horses and men stationed all along it. Darius himself may have ordered surrender in the hope of saving the city from sack. It was spared; with the ironic result that it survives today only as a mound. (The impressive fortress which crowns it was built not by Alexander, but by nineteenth-century archaeologists as a necessary refuge from the local tribesmen.) However, it was then the administrative capital of the empire and chief royal seat, built in an out-thrust of the Mesopotamian plain on the threshold of the Iranian plateau. Fragments from the palace suggest bright glowing surfaces of glazed ceramics, mostly blue and yellow moulded in relief. In its treasury, Alexander found the enormous sum—not counting jewels, which were never even approximately valued—of 40,000 talents in silver, and 9,000 darics in gold. Reckoned by Wilcken in 1931 as somewhere near £14,000,000, it could only be thought of today in terms of Fort Knox.
The house of the king-making eunuch vizier, Bagoas, forfeit at his death to Darius, was found to contain a thousand talents’ worth of rich robes alone. Plutarch says that the house and all its contents were presented to Parmenion. Among the palace treasures, a specially precious casket was taken by Alexander to house his copy of the Iliad, edited for him by Aristotle when he was a boy. It still lived in the bed box under his pillow. The dagger must have been kept in quicker reach. There would be more times than one when he would be close to needing it.