Battle in northern Greece (480 BC) in the Persian Wars .
The Greek forces, mostly Spartan, were led by Leonidas . After three days of holding their own against the Persian king Xerxes I and his vast southward-advancing army, the Greeks were betrayed, and the Persians were able to outflank them. Sending the main army in retreat, Leonidas and a small contingent remained behind to resist the advance and were killed to the last man.