The Achaemenid Persian empire was the largest that the ancient world had seen, extending from Anatolia and Egypt across western Asia to northern India and Central Asia. Its formation began in 550 B.C., when King Astyages of Media, who dominated much of Iran and eastern Anatolia (Turkey), was defeated by his southern neighbor Cyrus II (“the Great”), king of Persia (r. 559–530 B.C.). This upset the balance of power in the Near East. The Lydians of western Anatolia under King Croesus took advantage of the fall of Media to push east and clashed with Persian forces.