Part Two of our Thermopylae series. Read Part One: Before the Pass.
The Numbers
Herodotus put the Persian force at more than five million people and one and a half million fighting men. No serious historian believes this. The figure appears to come from adding up every contingent named in an imperial muster list, then multiplying, then multiplying again for camp followers. The logistics alone refute it — an army that size would drink rivers dry and starve within a week on the roads that existed.
Modern estimates range widely, from about seventy thousand to perhaps three hundred thousand combatants, with most careful work landing somewhere in the low-to-mid hundreds of thousands including support. Even at the low end it was, by a wide margin, the largest force ever brought against Greece, and it arrived with a fleet of several hundred warships and a supply train prepared over four years.
The Greek side is easier to count, because Herodotus lists the contingents one by one. What went to the pass was roughly seven thousand men:
Sparta: 300 hand-picked Spartiates under Leonidas — every one of them a man with a living son
Tegea: 500. Mantinea: 500. Arcadian Orchomenus: 120. Other Arcadians: 1,000
Corinth: 400. Phlius: 200. Mycenae: 80
Thespiae: 700, under Demophilus
Thebes: 400
Phocis: 1,000, plus the Opuntian Locrians, who sent everything they had
Along with the Spartiates came helots — the enslaved population that Sparta's whole system rested on — as attendants and light troops, uncounted by Herodotus because men like him did not count them. Later sources add perioikoi, free non-citizens of Spartan territory, in the hundreds. The true figure at the pass was likely closer to seven or eight thousand than to the three hundred of the poster.
Three hundred Spartans went to Thermopylae. Seven thousand Greeks went to Thermopylae. Both statements are true, and only one of them is the story.
Why so few? Because it was August, and two things were happening at once. Sparta was in the middle of the Carneia, a religious festival during which its army did not march. All of Greece was in the middle of the Olympic truce. The Spartan authorities sent Leonidas ahead with a bodyguard-sized force and told him the main army would follow when the festival ended. Whether they meant it is one of the oldest arguments in the field. Herodotus reports it as fact. Others have read it as a face-saving cover for a decision, already made, to fall back to the Isthmus of Corinth and defend the Peloponnese alone.
Leonidas chose his three hundred from men who already had sons. The practical reading is that he expected to lose them and did not intend to end anyone's family line. He knew what he was walking into before he left home.
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