Leonidas I (Greek: Λεωνίδας) (c. 530–480 B.C.) was a king of the Greek city-state of Sparta from about 490 BC until his death in 480. The Spartans and associates defended the pass at Thermopylae against the Persian army. Although Leonidas lost the battle, his death at Thermopylae was seen as a heroic sacrifice. Leonidas sent most of his army away when he realized that the Persians had outmaneuvered him. Three hundred of his fellow Spartans stayed with him to fight and die. Almost everything that is known about Leonidas comes from the work of the Greek historian Herodotus (c. 484–c. 425 BC)