Cambyses II, a king of Persia who ruled from 529 to 521 B.C. He succeeded his father, Cyrus the Great, as king. Cambyses completed the conquest of the East, begun by his father, by conquering Egypt in 525 B.C. While he was away, a pretender usurped the throne of Persia. In 521, on his way home, Cambyses died, either by suicide or by accident.