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Virtue & Power

The second Persian invasion of Greece

Thermopylae

A Greek force held a coastal pass in central Greece for three days against the army of Xerxes, and was destroyed when the position was turned by a mountain path.

480 BCE · Near Lamia, central Greece

The forces, and what the figures are worth

The Greek alliance

Leonidas I of Sparta · Demophilus of Thespiae

Evidence level: Documented

Greek troops in the initial force

About 5,200, including 300 Spartiates

Herodotus 7.202-203

Herodotus itemises the contingents, and the list is internally consistent. The famous 300 are the Spartiate citizens only; the force was roughly seventeen times that size, and the helots who accompanied the Spartans are not counted at all.

Evidence level: Disputed

Greeks remaining for the final stand

The 300 Spartiates, about 700 Thespians and about 400 Thebans

Herodotus 7.222

Herodotus states that Leonidas dismissed the other contingents. The Thespians stayed voluntarily and were destroyed; his account of the Thebans as unwilling hostages who surrendered is widely regarded as reflecting later Athenian hostility to Thebes rather than what happened.

The Achaemenid army

Xerxes I · Hydarnes, commander of the Immortals

Evidence level: Literary

Persian fighting men

1,700,000 infantry, with 80,000 cavalry and allied contingents bringing the total above five million with camp followers

Herodotus 7.60, 7.184-186

Universally rejected. An army of this size could not have been fed or watered on the route described, and Herodotus's own account of the counting — men herded in batches of ten thousand into a pen at Doriscus — reads as a story about scale rather than a return. The figure is the standard example of ancient numerical rhetoric.

Evidence level: Disputed

Persian fighting men

Roughly 70,000 to 150,000

Modern reconstruction from logistics, road capacity and water supply

Modern estimates vary by a factor of several and none commands consensus. What is agreed is that the Persian force was very large by the standards of the period and much smaller than Herodotus says.

What happened

The Greek alliance chose to hold the pass at Thermopylae in conjunction with a fleet action at Artemisium, so that the Persian army and navy could not support each other along the coast road.

For two days the Greeks held the narrow ground, where numbers could not be brought to bear and where heavy infantry in close order had every advantage. Herodotus reports that Xerxes sent in his best troops, the Immortals, and that they fared no better.

A local man, Ephialtes, showed the Persians the Anopaia path over the mountain. The Phocian contingent posted to guard it was brushed aside at dawn.

Learning that the position was turned, Leonidas dismissed most of the allied contingents and remained with the Spartiates, the Thespians and a Theban force. They were surrounded and killed. Herodotus reports that the body of Leonidas was recovered by the Persians and treated with a dishonour he regards as uncharacteristic of Xerxes.

Tactics

Thermopylae is the clearest ancient demonstration of terrain as a force multiplier. In the pass, a Persian army's advantages — numbers, cavalry, massed archery — could not be applied, while the Greek advantages of armour, the long thrusting spear and close order were decisive. The position had one weakness, the mountain path, and the campaign turned on it. The Greek plan was not a suicide mission but a delaying action tied to the fleet; it failed because the flank could not be held.

Consequence

Strategically the delay was modest and central Greece was lost with it; Athens was evacuated and burned. The Greek fleet withdrew from Artemisium and fought at Salamis weeks later. The battle's importance is disproportionate to its military result, and always has been: the Greeks themselves made it a monument, and the epitaph attributed to Simonides for the Spartan dead was set up at the site.

Location

Evidence level: Documented

The pass of Thermopylae, the Hot Gates, between Mount Kallidromo and the Malian Gulf

Modern: Near Lamia, central Greece

The pass is securely identified, but the ground has changed beyond recognition. Silt from the Spercheios river has moved the coastline several kilometres seaward, so the narrow track between cliff and sea that made the position defensible is now an inland plain.

Archaeology

Evidence level: Probable

Excavation on the Kolonos hill, the traditional site of the final stand, recovered a concentration of bronze and iron arrowheads consistent with the account of the last phase. The identification of the hill is generally accepted. The silted coastline means the tactical ground cannot be reconstructed with confidence.

Open questions

Evidence level: Disputed

Was the stand a deliberate sacrifice?

Herodotus reports an oracle that Sparta must lose a king or lose the city, and presents Leonidas as acting on it. Whether this is a motive or a retrospective explanation is not recoverable. The alternative reading is a rearguard: the allies were dismissed to save them, and a covering force stayed to buy the withdrawal time.

Evidence level: Disputed

How large was the Persian army?

Herodotus's figures are rejected by everyone; what should replace them is not agreed. Estimates from 70,000 to 300,000 have serious defenders, and the disagreement turns on logistics — how much water the route could supply and how fast a column of a given size could move.

Primary sources

  • Herodotus, Histories 7.175-239

    The only substantial ancient narrative, written roughly a generation later.

  • Diodorus, Diodorus Siculus, Library of History 11.4-11

    A later account drawing on Ephorus, differing from Herodotus in several details.

Reception

No ancient battle has been more heavily appropriated. Thermopylae has been recruited by nineteenth-century nationalisms, by the Axis and by the Allies in the same war, and by modern political movements of several kinds. Readers will meet the battle through those uses before they meet Herodotus. The platform records this as reception; it does not license any of it, and it does not treat the Spartan state — a society resting on the systematic subjection of the helots — as an object of admiration.

How to read the evidence labels

Evidence level: Documented
Supported by a named primary text or by excavated material evidence.
Evidence level: Probable
Supported by strong inference that most specialists accept.
Evidence level: Disputed
Substantial specialist disagreement exists; competing readings are stated.
Evidence level: Literary
Belongs to poetic or mythological construction rather than to history.
Evidence level: Mythological
Belongs to shared religious or mythic tradition rather than to any single text.
Evidence level: Unknown
The available evidence is insufficient to decide.

These labels describe the status of the evidence, not our confidence in a conclusion. A claim marked Literary is not a claim we doubt; it is a claim about what kind of thing a poem is.