Greece and the Balkan Peninsula secured, Alexander then crossed (334) the Hellespont (now the Dardanelles) and, as head of an allied Greek army, undertook the war on Persia that his father had been planning. The march he had begun was to be one of the greatest in history. At the Granicus River (near the Hellespont) he met and defeated a Persian force and moved on to take Miletus and Halicarnassus. For the first time Persia faced a united Greece, and Alexander saw himself as the spreader of Panhellenic ideals. Having taken most of Asia Minor, he entered (333) N Syria and there in the battle of Issus met and routed the hosts of Darius III of Persia, who fled before him.
Alexander, triumphant, now envisioned conquest of the whole of the Persian Empire. It took him nearly a year to reduce Tyre and Gaza, and in 332, in full command of Syria, he entered Egypt. There he met no resistance. When he went to the oasis of Amon he was acknowledged as the son of Amon-Ra, and this may have contributed to a conviction of his own divinity. In the winter he founded Alexandria, perhaps the greatest monument to his name, and in the spring of 331 he returned to Syria, then went to Mesopotamia where he met Darius again in the battle of Guagamela. The battle was hard, but Alexander was victorious. He marched S to Babylon, then went to Susa and on to Persepolis, where he burned the palaces of the Persians and looted the city.
He was now the visible ruler of the Persian Empire, pursuing the fugitive Darius to Ecbatana, which submitted in 330, and on to Bactria. There the satrap Bessus, a cousin of Darius, had the Persian king murdered and declared himself king. Alexander went on through Bactria and captured and executed Bessus. He was now in the regions beyond the Oxus River (the present-day Amu Darya), and his men were beginning to show dissatisfaction. In 330 a conspiracy against Alexander was said to implicate the son of one of his generals, Parmenion; Alexander not only executed the son but also put the innocent Parmenion to death. This act and other instances of his harshness further alienated the soldiers, who disliked Alexander's assuming Persian dress and the manner of a despot.
Nevertheless Alexander conquered all of Bactria and Sogdiana after hard fighting and then went on from what is today Afghanistan into N India. Some of the princes there received him favorably, but at the Hydaspes (the present-day Jhelum River) he met and defeated an army under Porus. He overran the Punjab, but there his men would go no farther. He had built a fleet, and after going down the Indus to its delta, he sent Nearchus with the fleet to take it across the unknown route to the head of the Persian Gulf, a daring undertaking. He himself led his men through the desert regions of modern Baluchistan, S Afghanistan, and S Iran. The march, accomplished with great suffering, finally ended at Susa in 324.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.