In the summer of 323 BC, word reached Greece that Alexander the Great was dead at Babylon, thirty-two years old, his empire stitched together by force and held by no clear heir. For the Greek cities that Macedon had subdued, the news was an opening. Athens, never reconciled to foreign domination, raised an army and called allies to its banner. The Aetolian League joined. So did city after city across central Greece. The war that followed is known as the Lamian War, and its opening move was to do what Greeks had done in Xerxes' day: hold the gate at Thermopylae before the northern army could pour south.

Antipater had governed Macedon for years while Alexander campaigned in Asia, a steady hand in a kingdom of restless ambitions. When rebellion flared, he sent urgent messengers to Craterus and Philotas in Asia, asking the veterans there to bring their ten thousand and more to his aid. But he could not wait for them. He marched south into Thessaly with thirteen thousand foot soldiers and six hundred horsemen, leaving Sippas to hold Macedon behind him. It was a respectable army. It was not, as events would prove, a large enough one.

The Thessalians decided the day before the fighting truly began. They had ridden out as Macedon's allies — their cavalry was famous, the best in Greece — but as Antipater advanced they changed sides, throwing in with the Athenian general Leosthenes and his coalition already massing at the pass. Suddenly the defenders held both the chokepoint and the better horse. Antipater was outnumbered and outmaneuvered in the one place where numbers and ground decide everything. The battle went against him. The man who had outlasted Alexander now found himself the trapped one at Thermopylae.

Defeat at the pass left Antipater nowhere to run. With the coalition's forces stronger than his own and the Thessalian cavalry able to harry any retreat, he shut himself and his army inside the walled city of Lamia, a few miles north of the battlefield. There Leosthenes besieged him, and for a season it seemed the Greeks might end Macedonian rule entirely. Then fortune turned again. Leosthenes was killed beneath the walls — struck, the sources say, by a stone hurled from the ramparts — and the siege lost its driving force. The Lamian War would grind on, and Macedon would ultimately reassert its grip on Greece. But for one summer, in the shadow of Leonidas' legend, the gate at Thermopylae had belonged to the Greeks again.

Why here, again? Because geography does not change. Thermopylae — the 'Hot Gates,' named for its sulphurous springs — was for centuries the doorway between northern and southern Greece, a ribbon of passable ground pinched between the steep flank of Mount Kallidromon and the marshy shore of the Malian Gulf. Any army moving down the eastern coast had to thread it. The sea has since retreated, leaving a broad coastal plain where ancient ships once nearly touched the cliffs, so the modern traveler must imagine the squeeze. But stand on this ground and the logic of a thousand years of battles becomes plain: whoever held the narrows held Greece.