When Philip divorced Olympias to marry a younger princess, Alexander fled. Although allowed to return, he remained isolated and insecure until Philip's mysterious assassination about June 336 BC. Alexander was at once presented to the army as king. Winning its support, he eliminated all potential rivals, gained the allegiance of the Macedonian nobles and of the Greeks (after a battle, in which he destroyed THEBES), and defeated the neighboring barbarians.
Then he took up Philip's war of aggression against Persia, adopting his slogan of a Hellenic Crusade against the barbarian. He defeated the small force defending Anatolia (Turkey), proclaimed freedom for the Greek cities there while keeping them under tight control, and, after a campaign through the Anatolian highlands (to impress the tribesmen), met and defeated the Persian army under Darius (not the same Darius as in the Persian Wars)
He occupied Syria and--after a long siege of TYRE--Phoenicia, then entered Egypt, where he was accepted as pharaoh.
From there he visited the famous Libyan oracle of AMON (or Ammon, identified by the Greeks with Zeus). The oracle certainly hailed him as Amon's son (two Greek oracles confirmed him as son of Zeus) and may have promised him that he would become a god. His faith in Amon kept increasing, and even in his lifetime he was portrayed on coins with the god's horns.
After organizing Egypt and founding the city of ALEXANDRIA, Alexander crossed the Eastern Desert and the Euphrates and Tigris rivers, and in the autumn of 331 BC defeated Darius's grand army at Gaugamela (near modern Irbil, Iraq).
Darius fled to the mountain residence of ECBATANA, while Alexander occupied BABYLON, the imperial capital SUSA, and PERSEPOLIS.
Henceforth, Alexander acted as legitimate king of Persia, and to win the support of the Iranian aristocracy he appointed mainly Iranians as provincial governors. Yet a major uprising in Greece had him so deeply worried that he delayed at Persepolis until May 330 BC and then, before leaving, destroyed the great palace complex as a gesture to the Greeks. At Ecbatana, after hearing that the rebellion had failed, he proclaimed the end of the Hellenic Crusade and discharged some of the Greek forces. He then pursued Darius, who had turned eastward. Darius was at once assassinated by Bessus, the satrap of Bactria, who distrusted his will to keep fighting and proclaimed himself king.
As a result, Alexander now faced years of guerrilla war in northeastern Iran and central Asia, which ended only when he married (327) ROXANA, the daughter of a local chieftain. The whole area was fortified by a network of military settlements, some of which later developed into major cities.
During these years, Alexander's increasingly Oriental behavior led to trouble with Macedonian nobles and some Greeks. PARMENION, Philip II's senior general, and his family originally had a stranglehold on the army, but Alexander gradually weakened its grip. Late in 330, Parmenion's oldest son, Philotas, commander of the cavalry and chief opponent of the king's new policies, was eliminated in a carefully staged coup d'etat, and Parmenion was assassinated. Another old-fashioned noble, Cleitus, was killed by Alexander himself in a drunken brawl. (Heavy drinking was a cherished tradition at the Macedonian court.) Alexander next demanded that Europeans follow the Oriental etiquette of prostrating themselves before the king--which he knew was regarded as an act of worship by Greeks. But resistance by Macedonian officers and by the Greek Callisthenes (a nephew of Aristotle who had joined the expedition as the official historian of the crusade) defeated the attempt. Callisthenes was soon executed on a charge of conspiracy.
With discipline restored, Alexander invaded (327) the Punjab. After conquering most of it, he was stopped from pressing on to the distant Ganges by a mutiny of the soldiers. Turning south, he marched down to the mouth of the Indus, engaging in some of the heaviest fighting and bloodiest massacres of the war. He was nearly killed while assaulting a town. On reaching the Indian Ocean, he sent the Greek officer Nearchus with a fleet to explore the coastal route to Mesopotamia. Part of the army returned by a tolerable land route, while Alexander, with the rest, marched back through the desert of southern Iran, chiefly to emulate various mythical figures said to have done this. He emerged to safety in the winter of 325-24, after the worst sufferings and losses of the entire campaign, to find his personal control over the heart of the empire weakened by years of absence and rumors of his death. On his return, he executed several of his governors and senior officers and replaced others.
He also ordered the governors to dismiss their mercenary armies, originally enrolled at his direction but now a cause of fear. Most of the mercenaries were exiled Greeks. The loss of their livelihood by tens of thousands of these men caused a grave social crisis. Alexander passed the problem on to the Greek cities by arbitrarily commanding them to readmit all their exiles. One side effect was a move to offer him deification (which some Greeks in Anatolia had perhaps already begun to do) in order to obtain concessions. Though the move was not due to his own initiative, this shows what he was thought to want. In Athens and perhaps elsewhere, the deification was passed after considerable resistance.
In the spring of 324, Alexander held a great victory celebration at Susa. He and 80 close associates married Iranian noblewomen. In addition, he legitimized previous informal marriages between soldiers and Persian women and gave them rich wedding gifts, no doubt to encourage such unions. When he discharged the disabled Macedonian veterans a little later, after defeating a mutiny by the estranged and exasperated Macedonian army, they had to leave their wives and children with him. Because national prejudices had prevented the unification of his empire, his aim was apparently to prepare a long-term solution (he was only 32) by breeding a new body of high nobles of mixed blood and also creating the core of a royal army attached only to himself. After his death, nearly all the noble Susa marriages were dissolved.
In the autumn of 324 BC, at Ecbatana, Alexander lost his boyhood friend Hephaestion, by then his grand vizier--probably the only person he had ever genuinely loved. The loss was irreparable. After deep mourning, he embarked on a winter campaign in the mountains, then returned to Babylon, where he prepared an expedition for the conquest of Arabia. He died in June 323 BC without designating a successor. His death opened the anarchic age of the DIADOCHOI.