His pretext, said his officer Aristobulus, was that the Arabs had never sent him an embassy, 'but in fact, he was insatiable for conquest, wishing to be master of everybody'. His armies had spilled into Italy and India, along the Black Sea and north to the Danube, and it is a frequent mistake to rationalize men's motives for war, as if they fought more for profit than glory. However, there was another side to the Arab expedition as well as mere universal conquest: in the Hadramut valley, spices grew so prolifically that the Arabs used them instead of firewood, sending a steady surplus north by camel and caravan, whose scent was such that the 'drivers become drowsy and only overcome their drowsiness by sniffing asphalt or the skin of goats'. By raft, these spices travelled to the mouth of the Euphrates, then up-stream to Babylon by rivercraft, and so on foot to the city itself: there were myrrh and frankincense, oases of cassia, bushes of naturalized cinnamon and fields of self-sown spikenard. To a man whose palace floor was strewn with sweet scent, these luxuries were irresistible. Alexander was also excited by the reports of harbours along the Arabs' coastline. New Alexandras could be developed to guard the trade route round Arabia to the Red Sea and the Persian Gulf and grow rich and famous on its profits: a thousand talents annually of frankincense had once been paid by southern Arabia as tribute to the Persian kings, and although an old eastern proverb had said 'never show an Arab the sea or a Phoenician the desert', there was no reason why these spices could not be diverted from caravans to the fleet.

The plan had formed in his mind at least since his meeting with Nearchus in Kirman. There they had talked of the Persian Gulf's signs of a spice route, and four explorers had been sent one after another in thirty-oared craft to trace it back to its source. The first was one of Nearchus's fellow-captains who sailed south only as far as Bahrein; the second, son of an exiled Athenian general, was following him in the winter after Hephaistion's death and left a most observant account of Bahrein's natural history, down to the mangrove trees and orange groves which still distinguish it. He too went no farther. At the same time a third captain had set out on the reverse journey, from the Suez Canal, down the Red Sea and round Arabia into the Persian Gulf; heat and thirst defeated him and he turned back half way. The fourth explorer, a Cypriot, was bolder: he sailed as far as the Aden promontory, 'but despite orders to sail round to Egypt, he became afraid and returned, reporting that Arabia was even larger than India'. The route, however, had been sailed by local traders without fuss or fear for at least two thousand years.

Both the exploration of the Caspian and the conquest of Arabia were attainable ambitions and they speak for Alexander's continuing art of the possible. Neither was as original as it seemed to him: empires might rise and fall by sarissa and cataphract, but since the first dynasty of the Pharaohs, trade had been flowing from the Red Sea, Egypt and the kingdom of Punt, past Bahrein's island and up to the Persian Gulf. Scylax the sea-captain, everywhere a forerunner, had already found the secret of the Caspian's sources: he, too, had sailed round Arabia, beginning from the Red Sea and emerging into the Persian Gulf, ready to report on the need for repairing the Pharaoh's Suez Canal. Encouraged, his patron Darius I had cleared the canal and reopened the route from Persia, round Arabia, to the Mediterranean and this route had been used by ambassadors from the Aegean and traders from Phoenicia alike. At best, Alexander would regain the Persians' former knowledge of their empire's seas; at worst, he would have encouraged a trade route as old as history itself, for once more he came, unwittingly, to restore and to develop, not to change.

There were those in camp who had urged a more novel expedition: 'At a festival in Hamadan,' wrote Ephippus, 'Gorgo the royal munitions officer, a Greek from the island of Iasos, crowned Alexander son of Ammon with three thousand golden crowns and announced that when he besieged Athens, he would supply him with ten thousand suits of armour and as many catapults.' It was true that at Hamadan, an attack on Athens could well have been discussed by junior officers: Harpalus had fled there, and he had been received after a first refusal, while the city continued to elect as its yearly generals men who were known to be implacably opposed to the Macedonians, even choosing that same Thrasybulus who had caused Alexander such trouble at the siege of Halicarnassus ten years earlier. There was also the matter of Athens's tenancy of Samos which the decree to restore Greek exiles had suddenly endangered. Alexander had already announced in camp that he would 'give Samos to the Samians', but this may only have been a calculated threat on news of Harpalus's activities: however, the Athenian settlers on the island has served as a base to the Persian navy during the war in the Aegean, and the memory was not in their favour. Ephippus, as usual, knew how to rouse recent malice. Gorgo's name was loathsome to most Athenians, as he had had local contacts with the debate over Samos, and had vigorously pressed the Samian exiles' cause; thanks to men like Gorgo, the outlook for Athens's settlers was bad, and in autumn 324 the shrewder Athenians were already turning to flattery in order to save the island. Under the shadow of Samos they had been debating whether Athens should worship Alexander as a god: Demades had reminded his audience that 'they should not safeguard heaven, only to find they had lost the earth', while Demosthenes had commented that 'Alexander could be recognized as son of Zeus, for all he cared—and son of Poseidon too, if he really wanted', as long as this recognition seemed likely to save the Samian settlers. Alexander, as Athens agreed, was invincible, but he could at least be humoured with an offer of the worship which he was known to enjoy from Greeks elsewhere. Nobody objected to the principle of worshipping a living man, only to the fact that the man was their 'tyrant' Alexander. But diplomacy overcame disgust, and in the autumn of Hephaistion's death Athenian envoys set out with other Greeks to greet Alexander as a god, then put their case to him.

It is easily forgotten that the decision to restore the Samians had been received with delight by other Greek ambassadors. From Hamadan Alexander had no reason for besieging Athens into the bargain; Ephippus wrote gossip after his death and only put Gorgo's name to the proposal as a plausible touch of malice. As for his crowning as son of Ammon, the conceit seemed credible to contemporaries, and neither Ephippus nor hostile Athenians cared much for the truth; a letter was later invented, written as if to Athens about the ownership of Samos, in which Alexander was made to refer to Philip as merely his 'so-called father', and confirm, by implication, the Athenians' claim to the island. His true view of Ammon was less extreme, and in any case, it hardly befitted Athenians to mock the rumoured flatteries of Gorgo, when within twenty years, they themselves were hymning one of Alexander's Successors as a true 'child of the Sun and the goddess Aphrodite'.

Nonetheless, Alexander's threat had outraged Athens at a time when his position in Greece was not as secure as it often had been. Heavy new drafts of reinforcements were being summoned east from Macedonia to repair the gaps of Makran, and not only was the country's manpower strained by the demand, but Europe was also about to change its general. Antipater was aged over seventy and through letters and embassies, he had long been the subject of complaint, both from Olympias and Greek democrats; Alexander had maintained silence in the face of them, but he did once complain that his mother was punishing him hard for the mere nine months it had taken her to bear him. While Olympias was queen and Antipater mere general, there could never be peace between them. Now Craterus was approaching with orders to replace the general, perhaps temporarily while he visited Asia, perhaps for longer, as Alexander might wish to keep Antipater in Asia as second-in-command for all that gossip knew. It would be some months yet before Craterus returned, in poor health and with 10,000 veterans; his ageing troops were planning to winter in Asia, as Alexander had always allowed them, and for choice they would not leave the coast until summer, when sailing was easier; however, there were local disturbances in Cilicia which might delay them longer. They had only left for home after losing a mutiny, and they were not in any hurry; there was, however, a risk that Athens might abandon all reason and fight for the right to Samos before they returned. News of the recent rebellion in Thrace and the heavy Macedonian defeat on the Danube could only encourage their enterprise.