Leonidas (c. 530-480 B.C.) was a king of the city-state of Sparta from about 490 B.C. until his death at the Battle of Thermopylae against the Persian army in 480 B.C. Although Leonidas lost the battle, his death at Thermopylae was seen as a heroic sacrifice because he 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 B.C.).