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Philip II, in his 20s when he ascended the throne of Macedon in 359 B.C., had ambitious ideas for his backward realm at the edge of the feuding city-states of Greece. Under his rule, Macedonian nobles grew richer and understood that the rewards for loyalty to Philip were very real. But Philip had aspirations that went far beyond Macedon, and he began systematically quelling the fractious city-states to the south. By 338, having defeated Athens and Thebes at Chaeronea, he was the undisputed master of Greece.

Philip was not done. To the east lay the Persian Empire, massive in size and fantastically wealthy. Precisely when Philip made the decision to mount an invasion of it is unknown, but the idea for a war with Persia had many proponents in Greece. One of the most articulate was Isocrates of Athens. In 346 he had written his Address to Philip, a tract in which he called on the Macedonian king to lead a pan-Hellenic attack on Persia.

The Persians, Isocrates had explained, were womanly, cowardly, and unskilled in war, and Philip should use his military power against them. “It is your privilege as one who has been blessed with untrammeled freedoms, to consider all Greece your fatherland.” The fact that the Greek cities of Asia Minor were still under the Persian thumb would serve to unite the Greeks, and that in turn would put an end to their infighting. “It is much more glorious,” Isocrates counseled, “to fight against the [Persian] king than to contend against each other.”

His was just one voice calling for what became a ubiquitous idea among the Greeks—that they make common cause against Persia. Given the immensity of that empire, which stretched from Asia Minor to the frontiers of the Indian subcontinent, an invasion of Persia would be a monumental undertaking. But Philip had the funds to recruit and equip a fine army. He had acquired valuable deposits of gold and silver, and the money from the mines had helped fuel Philip’s maneuverings, allowing him to buy off invaders and those he wanted to bring under his wing. He was fond of saying that he had enlarged Macedon “far more by the use of gold than arms.”

The time to mount a successful attack on Persia grew more opportune when a young, inexperienced king, Arses, ascended the throne in 338. All that remained for Philip to implement his invasion was to rally the city-states of Greece and their substantial military resources round his banner.

In the winter of 338–337 Philip called other Greeks to a conference in Corinth. They quickly understood that his invitation was more summons than request. Delegates from every city-state except Sparta, which was implacable in its opposition to Macedonian imperialism, hastened to attend. The topic to be discussed was the creation of a common and lasting peace among all the Greeks that would be upheld by the collected city-states and guaranteed by Macedon.

In addition to the prospect of peace, each city-state would receive votes in the General Synod of the Common Peace— the number of its votes in proportion to its military contribution. The synod would judge disputes between states, and when required, elect a hegemon to use military force to set matters right. Delegates also pledged that their states would never take hostile action against another member state or against Philip or his descendants. Considering Macedon’s overweening power, the delegates had little other choice.

More a disguised imperial arrangement than a consenting union, the League of Corinth at least left its members with some of their self-respect and made it possible for Philip to control Greece efficiently without having to hold down all of its cities with garrisons.

Later in 337, the delegates of the new synod met again to consider an attack on Persia. While the proposed expedition has often been described, inaccurately and anachronistically, as a crusade, there was nonetheless a religious justification for it that helped Philip motivate the Greeks en masse. A century and a half earlier, invading Persians had despoiled Greek temples, including the Athenian temples of the Acropolis. Revenge for that affront was the basis of Philip’s proposal of war, and the synod approved it. Having already been elected hegemon, Philip was also appointed captain-general of the league, with the authority to raise an army and lead it against the Persians.

By early 336 a vanguard of that army had arrived in Asia Minor and taken control of the Hellespont. But Philip did not live to see his campaign come to fruition. Later that year he was assassinated by one of his bodyguards. Yet Philip’s death was not the end of the pan-Hellenic invasion. His son Alexander quickly took his place and reacted with the speed and determination that characterized all of his later campaigns.

When the Thebans rejected him as the new hegemon, Alexander deployed his army before their walls and cowed them into submission. The Athenians, though very hostile to Alexander, got the message and sent envoys to convey apologies for their tardiness in recognizing him. Within weeks of his father’s death, Alexander had reasserted Macedonian dominion over Greece.

Once more, league delegates, with the exception of the Spartans, traveled to Corinth, where they renewed their treaty with Macedon and voted to install Alexander as hegemon.

The young king took his father’s place as captain-general of the army in the war with Persia, his invasion force swelled by soldiers contributed by the members of the league. Under Alexander’s leadership, those troops helped spread Greek dominion far eastward and left the lasting stamp of Hellenism on a vast stretch of the ancient world. Even independent Sparta was brought into the fold in 331, after being defeated by Alexander’s Macedonian regent, Antipater.

In 323 Alexander died, and a year later the league came to an end when the once more rebellious Greeks were crushed by Antipater. Yet despite its short duration, the League of Corinth marked the first time that Greece was brought together as one political entity.


Attorney Marc G. DeSantis is a frequent contributor to MHQ’s War List and Laws of War.

Originally published in the January 2015 issue of Military History Quarterly. To subscribe, click here.