During the 4th century BC, the power of the independent Greek poleis (city-states), severely weakened by continuous internal conflict, particularly the Peloponnesian War and subsequent wars like the Corinthian War, began a slow but decisive decline. In this power vacuum, a burgeoning kingdom to the north, Macedonia, began to assert its influence over the Greek peninsula.
Philip II’s Rise to Hegemony
In 359 BC (not 360 BC), Philip II ascended to the throne of Macedonia. He was a highly ambitious and brilliant military strategist who radically transformed the Macedonian army, notably by introducing the Macedonian phalanx armed with the sarissa (an extremely long pike). Philip immediately began to involve himself in Greek internal politics, driven by a desire to secure Macedonia's borders and resources, and ultimately, to gain control over the wealthy south.
The first major confrontation came with the Third Sacred War (356–346 BC). This conflict erupted over the control of the sacred Sanctuary of Delphi. Philip II joined the war on the side of the Delphians, decisively defeating the Phocians in 346 BC. The peace treaty that followed, the Peace of Philocrates, formally granted Macedonia a permanent seat on the Amphictyonic Council (the body governing Delphi), effectively establishing Macedonia's political and military dominance over mainland Greece.
The Clash at Chaeronea
Some Greek poleis, particularly the democratic Athens, spearheaded by the orator Demosthenes, and the powerful Thebes, refused to accept Macedonian hegemony. Demosthenes delivered a series of impassioned speeches (The Philippics) urging resistance. In 339 BC, Philip used a minor conflict—the Fourth Sacred War—as a pretext to march his army deep into Greece. Athens and Thebes, recognizing the final threat to their independence, formed a desperate alliance.
The decisive battle was fought in Boeotia near the city of Chaeronea in 338 BC.
The Battle: Philip II commanded the Macedonian army, which included his elite unit, the Companions Cavalry.
Alexander's Role: Philip’s eighteen-year-old son, Alexander (the Great), commanded the Companions Cavalry on the Macedonian left flank. He personally led the critical charge that broke the Theban line.
The Sacred Band of Thebes: The Theban forces, positioned on the Greek left flank, were anchored by the legendary Sacred Band of Thebes, a crack unit of 300 hoplites composed exclusively of 150 pairs of male lovers. They fought with legendary ferocity, refusing to surrender or retreat. The entire unit was annihilated in their position, fighting to the last man.
Historian Plutarch famously recounted the scene where Philip II, surveying the battlefield and seeing the bodies of the Sacred Band lying together exactly where they had stood, was moved to tears by their bravery and devotion, allegedly declaring: "Perish miserably who suspect that these men either did or suffered anything base."
Aftermath: The League of Corinth
The victory at Chaeronea was absolute and marked the end of independent political power for the Greek city-states.
The following year, Philip II established the League of Corinth (also known as the Hellenic League). This was a military alliance that nominally united all Greek states (except Sparta) but was, in reality, a federation under the strict control and military dominance of Macedonia. Philip II was installed as the Hegemon (supreme commander). The primary purpose of the League was to launch a massive, Panhellenic invasion of the Achaemenid Persian Empire—a plan that would be carried out by his son, Alexander, after Philip's assassination in 336 BC.
