History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
And with them went an envoy from Tissaphernes, who was military governor of the coast-lands for King Darius[*](Darius II reigned 423-404.) son of Artaxerxes. For Tissaphernes was also trying to induce the Peloponnesians to come over to Asia, promising to furnish them maintenance.
For the King, as it chanced, had lately demanded of him the tribute from his own province, for which he had fallen into arrears, since he was not able to exact it from the Hellenic cities because of the Athenians. He therefore thought that if he should weaken the Athenians he would be better able to collect his tribute; he also intended at the same time to make the Lacedaemonians allies of the King, and, in accordance with the King's command, either to take alive or to kill Amorges, bastard son of Pissuthnes,[*](Mentioned as satrap at Sardis in 440 B.C. (i. 115) and again in 428 (iii. 31). Soon after the latter date he revolted. Tissaphernes was sent to suppress the revolt and, succeeding, became satrap himself.) who was in revolt in Caria. Accordingly the Chians and Tissaphernes were negotiating in common for the same object.