“Cambyses gave orders to his fleet to sail against Carthage, but the Phoenicians refused to obey. They submitted that they were bound by solemn engagements and that they would be guilty of a crime if they made war on a daughter-community. This unwillingness of the Phoenicians [to lend themselves to Cambyses’ designs against Carthage killed the project, since] [bracket in Toynbee] the remainder of the fleet was inadequate for the task. So, thanks to their Phoenician kinsmen, the Carthaginians escaped subjugation at Persian hands; for Cambyses felt it impolitic to try to coerce the Phoenicians, considering that they had come under Persian sovereignty voluntarily and that the naval power of the Persian Empire depended entirely on them” (Herodotus, Book III, chap. 19).
A Study of History, Vol VII, OUP, 1954 (footnote)