Leonidas (lēŏnˈĭdəs) [key], d. 480 B.C., king of Sparta. He succeeded (c.491 B.C.) his half-brother, Cleomenes I. When the Persians invaded Greece under Xerxes (480 B.C.), Leonidas with 300 Spartans and 5,000 auxiliaries was given the pass at Thermopylae to hold. There was treachery. Most of the Greeks got away, but the Spartans and 700 Thespians refused to flee and were killed. Herodotus immortalized the incident. See Persian Wars.
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