Regency and ascent of Macedon
At age 16, Alexander’s education under Aristotle ended. Philip waged war against Byzantion, leaving Alexander in charge as regent and heir apparent. During Philip’s absence, the Thracian Maedi revolted against Macedonia. Alexander responded quickly, driving them from their territory. He colonized it with Greeks, and founded a city named Alexandropolis.
Upon Philip’s return, he dispatched Alexander with a small force to subdue revolts in southern Thrace. Campaigning against the Greek city of Perinthus, Alexander is reported to have saved his father’s life. Meanwhile, the city of Amphissa began to work lands that were sacred to Apollo near Delphi, a sacrilege that gave Philip the opportunity to further intervene in Greek affairs. Still occupied in Thrace, he ordered Alexander to muster an army for a campaign in Greece. Concerned that other Greek states might intervene, Alexander made it look as though he was preparing to attack Illyria instead. During this turmoil, the Illyrians invaded Macedonia, only to be repelled by Alexander.
Philip and his army joined his son in 338 BC, and they marched south through Thermopylae, taking it after stubborn resistance from its Theban garrison. They went on to occupy the city of Elatea, only a few days’ march from both Athens and Thebes. The Athenians, led by Demosthenes, voted to seek alliance with Thebes against Macedonia. Both Athens and Philip sent embassies to win Thebes’ favor, but Athens won the contest. Philip marched on Amphissa (ostensibly acting on the request of the Amphictyonic League), capturing the mercenaries sent there by Demosthenes and accepting the city’s surrender. Philip then returned to Elatea, sending a final offer of peace to Athens and Thebes, who both rejected it.
As Philip marched south, his opponents blocked him near Chaeronea, Boeotia. During the ensuing Battle of Chaeronea, Philip commanded the right wing and Alexander the left, accompanied by a group of Philip’s trusted generals. According to the ancient sources, the two sides fought bitterly for some time. Philip deliberately commanded his troops to retreat, counting on the untested Athenian hoplites to follow, thus breaking their line. Alexander was the first to break the Theban lines, followed by Philip’s generals. Having damaged the enemy’s cohesion, Philip ordered his troops to press forward and quickly routed them. With the Athenians lost, the Thebans were surrounded. Left to fight alone, they were defeated.
After the victory at Chaeronea, Philip and Alexander marched unopposed into the Peloponnese, welcomed by all cities; however, when they reached Sparta, they were refused, but did not resort to war. At Corinth, Philip established a “Hellenic Alliance” (modeled on the old anti-Persian alliance of the Greco-Persian Wars), which included most Greek city-states except Sparta. Philip was then named Hegemon (often translated as “Supreme Commander”) of this league (known by modern scholars as the League of Corinth), and announced his plans to attack the Persian Empire.
Exile and return
When Philip returned to Pella, he fell in love with and married Cleopatra Eurydice, the niece of his general Attalus. The marriage made Alexander’s position as heir less secure, since any son of Cleopatra Eurydice would be a fully Macedonian heir, while Alexander was only half-Macedonian. During the wedding banquet, a drunken Attalus publicly prayed to the gods that the union would produce a legitimate heir.
At the wedding of Cleopatra, whom Philip fell in love with and married, she being much too young for him, her uncle Attalus in his drink desired the Macedonians would implore the gods to give them a lawful successor to the kingdom by his niece. This so irritated Alexander, that throwing one of the cups at his head, “You villain,” said he, “what, am I then a bastard?” Then Philip, taking Attalus’s part, rose up and would have run his son through; but by good fortune for them both, either his over-hasty rage, or the wine he had drunk, made his foot slip, so that he fell down on the floor. At which Alexander reproachfully insulted over him: “See there,” said he, “the man who makes preparations to pass out of Europe into Asia, overturned in passing from one seat to another.”
Alexander fled Macedon with his mother, dropping her off with her brother, King Alexander I of Epirus in Dodona, capital of the Molossians. He continued to Illyria, where he sought refuge with the Illyrian King and was treated as a guest, despite having defeated them in battle a few years before. However, it appears Philip never intended to disown his politically and militarily trained son. Accordingly, Alexander returned to Macedon after six months due to the efforts of a family friend, Demaratus, who mediated between the two parties.
In the following year, the Persian satrap (governor) of Caria, Pixodarus, offered his eldest daughter to Alexander’s half-brother, Philip Arrhidaeus. Olympias and several of Alexander’s friends suggested this showed Philip intended to make Arrhidaeus his heir. Alexander reacted by sending an actor, Thessalus of Corinth, to tell Pixodarus that he should not offer his daughter’s hand to an illegitimate son, but instead to Alexander. When Philip heard of this, he stopped the negotiations and scolded Alexander for wishing to marry the daughter of a Carian, explaining that he wanted a better bride for him. Philip exiled four of Alexander’s friends, Harpalus, Nearchus, Ptolemy and Erigyius, and had the Corinthians bring Thessalus to him in chains.