On learning this, Alcibiades was afraid, and departed from the camp altogether, and assembling mercenary troops made war on his own account against the Thracians who acknowledge no king. He got together much money from his captives, and at the same time afforded security from barbarian inroads to the Hellenes on the neighboring frontier.
Edition :
Plutarch Lives IV: Alcibiades and Coriolanus, Lysander and Sulla, Ed. Jeffrey Henderson, trans. Bernadotte Perrin (The Loeb Classical Library 80), Harvard University Press: Cambridge/MA - London 2000 (first ed. 1916).