In 336 B.C. Alexander the Great (336323) succeeded to the Macedonian throne and immediately invaded Illyria and Thrace. The following year inspired by a rumor that Alexander had died while on campaign, Thebes, Athens, Arcadia, Elis, and Aetolia revolted against Macedonian hegemony. Alexander swiftly moved south, took Thebes, destroyed it, and enslaved its inhabitants. The other revolting states submitted.
In the spring of 334 Alexander left Antipater as governor in Greece and crossed the Hellespont with an army of 32,000 infantry and 5,000 cavalry. The army was supported by a navy of 160 ships, mostly made up of Greek allies. Memnon of Rhodes, the commander of Greek forces in the Persian service, advised a tactical retreat, but the satraps insisted on fighting. The Persians were completely defeated by Alexander at the Battle of Granicus.
Most of the Greek cities of Ionia revolted against the Persians in 334-333. Memnon died and the Persian satrap Darius withdrew the Greek mercenaries into Syria, where he gathered a large army. Alexander subdued Caria and Cilicia, then advanced into Syria. He again defeated the Persian army, under the personal command of Darius III, at the Battle of Issus. After this defeat, Darius offered to give up all of Asia west of the Euphrates and to pay 10,000 talents, but Alexander demanded unconditional surrender. After Issus, all of Phoenicia except Tyre submitted to Alexander.
After a difficult siege of seven months, Tyre was captured in 332. The provinces of Galilee, Samaria, and Judah surrendered to Alexander. When he approached Egypt, its satrap turned the richest province of the Persian Empire over to Alexander without a fight.
During a year-long stay in 332-331, Alexander founded Alexandria on the coast of Egypt and visited the oracle of Ammon at the oasis of Siwa in the Western Desert, where he was proclaimed the son of a god.
Leaving Egypt during in the spring of 331, Alexander marched into Mesopotamia. In October he met and defeated another Persian army under Darius in the Battle of Gaugamela. Babylonia and Susa soon surrendered. One of the Persian capitals, Persepolis, was looted and burned, ostensibly in revenge for the destruction of Athens in 480.
The same year Sparta under King Agis III (338331), aided by Persian money and in alliance with Elis, Achaea, and part of Arcadia, defeated a Macedonian force and besieged Megalopolis. Antipater marched into the Peloponnese with a greatly superior force and crushed the Spartans and their allies.
In the spring of 330, Alexander pursued Darius through Media. Finally, the Persian king was murdered by the satrap Bessus. Alexander subdued the Caspian region and then marched southward. Once Parmenio's son Philotas had been executed for complicity in a plot, Alexander sent messengers who murdered Parmenio in Media: Alexander feared a revolt and Parmenio was too powerful to be discharged.
In 330 Athens had recouped its strength under the financial administration of Lycurgus. Compulsory military training for all youth (epheboi) was established. Demosthenes was acquitted in a trial brought by Aeschines on the legality of the award to Demosthenes of a civic crown.
The year 329328 Alexander marched into Bactria and Sogdiana, overcoming the Iranians under Spitamenes, but with difficulty. Alexander soon after adopted Persian dress and court etiquette, including proskynesis, or prostration before the king. In a drunken fury, he murdered his friend Cleitus who had reproached him for this. Alexander had 30,000 Persians trained to fight in the Macedonian fashion. Then Alexander married the Bactrian princess Roxane. Invited into India by "Taxiles" (King Ambhi of Taxila) against Porus (King Parvataka), Alexander crossed the Indus.
In 326 Alexander defeated Porus at the Battle of the Hydaspes (Jhelum) and advanced as far as the Hyphasis (Beas) River. At this point the Macedonian army refused to march any farther east.
The following year Alexander marched to the Indian Ocean via the Hydaspes and Indus. In a campaign against the Mallians, Alexander leapt alone from the wall of their city into the midst of the enemy. He was wounded by an arrow but rescued by his troops. In July, Nearchus set out with the fleet to return via the coast of the Indian Ocean and Persian Gulf. Alexander returned through the Gedrosian Desert, where the army suffered serious losses due to lack of supplies.
A Macedonian noble, Harpalus, guilty of embezzling massive funds while Alexander fought in India, fled to Athens in 325. He bribed many Athenian politicians, including Demosthenes, in an attempt to secure sanctuary.
In 324 Alexander's army and navy met in Caramania, and after resting, continued on to Susa. Alexander had left many of the native satraps in office, but most of these were now replaced by Macedonians. His friend Hephaestion was made hipparch, or second-in-command. Alexander married Barsine, the eldest daughter of Darius, and 80 of his officers took wives from the Persian and Median aristocracy. Alexander made official the unions of soldiers with concubines who had been taken along the route and paid all the debts of his soldiers. He ordered all exiles recalled by the Greek cities and ordered them to recognize him as the son of Zeus Ammon. He sent home 10,000 Macedonians considered no longer able to fight and replaced them with Persians and other Iranians. Hephaestion died at Ecbatana and was extravagantly mourned but not replaced as hipparch.
In 323 Alexander gathered a large army and navy at Babylon, apparently preparing for a campaign against Arabia. On June 13, 323 Alexander died of a fever at Babylon without clearly designating a successor. His death is generally considered the dividing point between the Classical and Hellenistic periods.