In 546 BC, Croesus of Lydia was defeated and captured by the Persians, who then adopted gold as the main metal for their coins. There are accounts in the biblical Book of Esther of dispatches being sent from Susa to provinces as far out as India and the Kingdom of Kush during the reign of Xerxes the Great (485–465 BC). By the time of Herodotus (c. 475 BC), the Royal Road of the Persian Empire ran some 2,857 km from the city of Susa on the Karun (250 km east of the Tigris) to the port of Smyrna (modern İzmir in Turkey) on the Aegean Sea.