CASUALTY RECORD // -190 BCE
Battle of Thermopylae
Estimated casualties — killed, wounded, captured, and missing — by side, with confidence labels per surviving record.
Casualties by side
1 sides catalogued · combined 12,000 estimated
Seleucid Empire
12,000
Medium-confidence figure
Battle context
The Battle of Thermopylae, fought on 24 April 191 BC, was a major engagement of the Roman–Seleucid War in which Roman forces under consul Manius Acilius Glabrio confronted the Seleucid-Aetolian army of Antiochus III the Great. The Roman Republic fielded approximately 25,000 troops against a Seleucid force of roughly 12,500. Seleucid casualties reached some 12,000, representing a near-total destruction of Antiochus's engaged force. The scale of those losses significantly degraded Antiochus III's capacity to sustain operations in Greece and undercut the Seleucid-Aetolian coalition that had formed to contest Roman influence in the region. The engagement was a decisive Roman success within the broader campaign that ultimately concluded with the Peace of Apamea in 188 BC, confirming Roman dominance over the Hellenistic east and sharply curtailing Seleucid power west of the Taurus Mountains.
‹ Full battle dossier