The palaces lacked no magnificence. 'The city', wrote a Thessalian companion, 'has no walls'; despite what many had believed, 'its circumference is twenty miles, and it lies at the far end of the Kara Su bridge'. It was thought by the Greeks to have been founded by Tithonus, hero of an endless old age, but in fact, it had been built by the first Darius nearly two hundred years before Alexander, and it lay in the land of the Elamites, once masters of an empire but long reduced by the Persians to service as scribes, palace guards and charioteers. Every province of the Great King had helped to build Susa. Sissoo-wood for the pillars had been shipped from India, craftsmen and goldsmiths had come from the cities of Greek Asia; among their carvings and goldwork, enamels, carpets and precious woods, Alexander found himself master of another gigantic treasure of bullion, this time a more personal legacy from the Persian kings. On the city's central platform, each king had built a treasury of his own; in the royal bedrooms, at the head and foot of the king's bed, stood two private treasure-chests, while the bed was guarded by the celebrated golden plane tree, so long a symbol of Persia's riches. No treasure was more impressive than the piles of purple embroidery, 190 years old but still as fresh as new from the honey and olive oil which had been mixed into their dyes. Heir to the most magnificient fortune in his world, Alexander had now entered a new scale of power altogether; it was only a beginning when 3,000 talents, six times the annual income of fourth-century Athens, were ordered to be sent to Antipater to help him with the Spartan revolt, still not known to have ended satisfactorily.

His entry to Susa was an emotional moment, for Greeks were celebrating the fall of a palace whose threats and money had determined so much of their affairs in the past eighty years. The occasion was not lost on Alexander: at Susa, he sacrificed to the Greek gods and held Greek gymnastic games, and on entering the inner palace, he was shown to the tall gold throne of the Persian kings where he took his seat beneath its golden canopy; Demaratus, giver of Bucephalas and most loyal of his Greek companions, 'burst into tears at the sight, as old men like to do, saying that a great pleasure had been missed by those Greeks who had died before they could see Alexander seated on Darius's throne'. But the height of the throne was an embarrassment, for whereas a Persian king would rest his feet on a stool, being too revered for his feet to touch the ground, Alexander needed not a footstool but a table, proof of his small size. A table was rolled to the throne, but the insult to Darius's furniture so upset an onlooking Persian eunuch that he burst into tears; Alexander hesitated, but at the suggestion of Philotas, Parmenion's elder son, he is said to have hardened his heart and left Darius's table under his feet. In that trivial moment of hesitation, his new problem had first been put to him, lightly though he passed it by. A Greek had wept for joy at what a Persian had lamented, and Alexander, the first man to rule both peoples, would soon have to compromise between them.

At Susa his attitude remained unashamedly Greek. As his new bargain required, the district was restored to the Persian satrap who had surrendered it, and a Macedonian general, treasurer, garrison and city commander were left beside him for safety and convenience. Other details were more telling. Inside the palace, statues were found of the two most famous Athenian popular heroes, revered as the slayers of Athens's last tyrant. Xerxes had taken them as loot from Athens in 480; Alexander ordered their return, a reply to those Athenians who called him a tyrant himself. He was not merely the avenger of Xerxes's wrongs. He was posing as a sympathizer with the most democratic cult in the Greek city whom he most feared. His publicity was as well informed as ever, perhaps on Callisthenes's advice. In return he left behind Darius's mother, daughters and the son whom he had captured at Issus, and appointed teachers to teach them the Greek language.

So far, in Susa and Babylon, his view of himself and his expedition had not been tested. At Babylon, he could continue to trade on the revenge for Xerxes which his father had once conceived for the Greeks; at Susa the Persians had first set up their palace 'because, most of all, the town had never achieved anything of importance but seemed to have always been subject to somebody else'. From Susa onwards he would no longer be passing through a long-subjected empire; he would not pursue Darius, rightly, until his flanks and rear were protected and the season allowed him to find supplies near Hamadan. His route now led him due east to the province of Persia, home of the empire's rulers. Here there was nobody to free or avenge; resistance was likely, and it would come from men who were fighting for their homes.

Leaving Susa in mid-December Alexander crossed the river Karun after four days, and received his first warning that the world beyond was different. In the hills above the road lived a large tribe of nomads who had always received dues from the Persian king in return for a safe passage through their grazing; this arrangement was new to Alexander and not to his liking, so in a dawn attack, whose two descriptions bear little resemblance to each other, he routed them and reduced them to pleading for their lands. They appealed to the Persian queen mother Sisygainbis, aunt of their leader; Alexander heeded her and granted the nomads continuing use of their lands at the cost of 100 horses, 300 baggage animals and 30,000 sheep, the only coin in which they could pay. The sheep were precious supplies, but in the unchanging balance of the East, where nomad and villager bargain and struggle for their rights against each other, it was no way to solve a problem which was as old as the landscape itself.

Three days' march beyond the nomads, danger took another turn. On the edge of the Persians' own homeland, it was natural to expect trouble, and Alexander recognized the task ahead by dividing his forces: where the road branched south-east Parmenion was to take the baggage and heavy-armed troops through modern Behbehan and Kazarun to Persepolis, ceremonial centre of the Persian empire, while the Companion Cavalry, the Foot Companions and the light-armed units were to follow their king eastwards into the province, up the rough but direct route through the mountains. Any pickets could thus be captured before they could fall back and warn against Parmenion. The sequel has been overshadowed by Gaugamela, but it was hardly the happiest memory of Alexander's career.

The road wound up through a narrow ravine to a height of 7,000 feet; it was flanked by thick oak forests, and a fall of snow had helped to conceal its pot-holes. On the fourth day the native guides pointed out the so-called Gates of Persia, a sheer mountain barrier which Arab geographers later praised as an earthly paradise; it was approached by a particularly narrow gorge and at the far end the rocks seemed to form a wall. Alexander entered it carefully, but no sooner was he committed than the wall was seen to be artificial; Persian catapults were mounted behind it and the heights on either side were swarming with Persians, 'at least 40,000 strong in the frightened opinion of Alexander's officers.

The pickets began an avalanche by rolling boulders down from the cliffs and the archers and catapults volleyed into an enemy 'trapped like bears in a pit'. Many Macedonians clawed for a hold to climb the rock walls but they only fell back in the attempt: there was nothing for it but to retreat, so Alexander led his survivors three and a half miles west to the clearing now known as Mullah Susan. Although an easier road was known to skirt the gorge in a wide north-easterly loop, he rightly refused to take it; he 'did not wish to leave his dead unburied', the concession of defeat in an ancient battle, and he could not risk a Persian retreat to Persepolis and an ambush of Parmenion and the approaching baggage-train. There seemed no way out until a captive shepherd told of a rough sheep track which led round behind the Persians' wall. Like so many guides and interpreters in history, he only half belonged to the society he now betrayed; he was half Lycian by birth and knew the mountains as an outsider. Such information was highly risky, but Alexander had to believe it.