In August or September of 480 BCE, a small Greek army led by the Spartan king Leonidas held the pass of Thermopylae against the army of Xerxes for three days. Its last stand became one of the most famous episodes in history.

The defenders

Leonidas brought three hundred Spartan citizens. Herodotus says he chose only men who had living sons, so that no family line would die out. But the Spartans were not alone. Allied contingents from the Peloponnese and central Greece joined them, bringing the total Greek force to around seven thousand men, according to most readings of Herodotus. Helots also accompanied the Spartans. The popular image of three hundred men fighting alone is a myth; the three hundred were the core of a larger army.

Why did Sparta send so few of its own? Herodotus explains that the Spartans were celebrating the Carneia festival, and the Olympic Games were under way; they planned to send the main army afterward. Some historians think Sparta also preferred to defend the Peloponnese itself, at the narrow Isthmus of Corinth, and sent Leonidas as a forward force.

The pass

At Thermopylae, the road ran between steep mountains and the sea, narrowing at points to a passage barely wide enough for a wagon or two. The Greeks rebuilt an old wall across it. In that narrow space, the Persians could not use their numbers or their cavalry, and they had to fight Greek heavy infantry, called hoplites, in close formation. Hoplites carried large round shields, long spears and short swords, and fought in a tight formation called the phalanx, each man's shield protecting his neighbor.

Days one and two

Xerxes waited several days, expecting the Greeks to flee. Herodotus says he sent a scout, who reported in amazement that the Spartans were exercising and combing their long hair. A Greek in Persian service explained that Spartans groomed their hair before facing death. When Xerxes demanded that they surrender their weapons, Leonidas is said to have replied, “Come and take them,” in Greek molon labe, a phrase recorded by Plutarch centuries later.

When the Persians attacked, wave after wave failed. Even Xerxes' elite guard, the Immortals, could not break through. The Spartans used tactics such as pretending to retreat, then turning on their pursuers. Herodotus says Xerxes leapt from his throne three times in fear for his army. A Spartan named Dieneces, told that the Persian archers were so numerous their arrows would blot out the sun, reportedly answered, “Good. Then we shall fight in the shade.”

The betrayal

Then, according to Herodotus, a local Greek named Ephialtes, hoping for a reward, told Xerxes about a mountain path, the Anopaea, that led around the pass to its rear. Leonidas had stationed a thousand Phocians to guard it, but they withdrew to a nearby hilltop when the Persians appeared at dawn. The Immortals marched through the night along the path. The name Ephialtes came to mean “traitor” or “nightmare” in Greek.

The last stand

Learning that the Greeks were about to be surrounded, Leonidas sent most of the allies away. He stayed with his three hundred Spartans, along with about seven hundred Thespians, who chose to remain, and about four hundred Thebans, whom Herodotus says Leonidas kept as hostages because Thebes was suspected of sympathizing with Persia. On the third day, the remaining Greeks advanced into the wider part of the pass and fought to the end. Leonidas was killed. The Spartans and Thespians fought over his body, retreated to a small hill, and died there under a hail of arrows. The Thebans surrendered.

The Thespians, who stayed and died alongside the Spartans by their own choice, are often forgotten in popular retellings. Their sacrifice was arguably even more remarkable, since they had no Spartan code demanding it.

The survivors

Two Spartans of the three hundred were absent from the final battle. Aristodemus, sent away with an eye disease, returned to Sparta and was shamed, called “the trembler.” He redeemed himself by fighting with reckless bravery and dying at Plataea a year later. Another, Pantites, sent away as a messenger, was so disgraced that he hanged himself.

The epitaph

A famous epitaph, attributed to the poet Simonides, was placed at the site. In a common translation: “Go tell the Spartans, stranger passing by, that here, obedient to their laws, we lie.”

Worked example: why fight to the death?

Historians have offered several explanations for Leonidas's decision to stay.

• Military. A rear guard could delay the Persians and protect the retreating allies, who would otherwise be caught and destroyed by cavalry on open ground.
• Religious. If Herodotus is right about the oracle, Leonidas may have believed his death would save Sparta.
• Cultural. Spartan law and honor forbade retreat. Surrender meant disgrace, as Aristodemus discovered.
• Symbolic. A heroic stand would inspire the other Greeks to keep fighting.

These explanations can all be true at once. Whatever Leonidas intended, the result was a defeat that worked like a victory in Greek memory. It also raises questions worth asking: what makes a sacrifice admirable rather than wasteful, and who decides that others should die for a cause? The Thespians and Thebans at Thermopylae made very different choices, or had them made for them.