Men of Bronze

"There was another thing which helped to bring about the Egyptian expedition. One of the Greek mercenaries of Pharaoh, being dissatisfied for some reason or other, escaped from Egypt by sea with the object of getting an interview with Cambyses. As this mercenary was a person of consequence in the army and had very precise knowledge of the internal condition of Egypt, Pharaoh was anxious to stop him …"

— Herodotus, The Histories