CASUALTY RECORD // -479 BCE
Battle of Thermopylae
Estimated casualties — killed, wounded, captured, and missing — by side, with confidence labels per surviving record.
Casualties by side
2 sides catalogued · combined 24,000 estimated
Greek city-states
4,000
Medium-confidence figure
Achaemenid Empire
20,000
Medium-confidence figure
Battle context
The Battle of Thermopylae was fought over three days at Thermopylae between the Achaemenid Persian Empire under Xerxes and an alliance of Greek city-states led by Sparta under Leonidas I. The Greek force numbered approximately 7,000 against a Persian army estimated at between 120,000 and 300,000. Greek casualties reached 4,000 against approximately 20,000 Persian dead. The engagement is recorded as one of the most prominent battles of both the Second Persian invasion of Greece and the wider Greco-Persian Wars. The disparity in casualties relative to force sizes reflects the nature of the contest: a substantially smaller Greek alliance inflicted disproportionate losses on the Persian force under Xerxes, with the Spartan contingent under Leonidas I joined by Thespian forces under Demophilus and Theban forces under Leontiades on the Greek side, and Persian command including Mardonius, Hydarnes, and Artapanus alongside Xerxes.
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