History of the Peloponnesian War

The engagement of the rest was more of a voluntary nature. It was less the league than hatred of the Lacedaemonians and the immediate private advantage of each individual that persuaded the Dorian Argives to join the Ionian Athenians in a war against Dorians; while the Mantineans and other Arcadian mercenaries, accustomed to go against the enemy pointed out to them at the moment, were led by interest to regard the Arcadians serving with the Corinthians as just as much their enemies as any others. The Cretans and Aetolians also served for hire, and the Cretans who had joined the Rhodians in founding Gela, thus came to consent to fight for pay against, instead of for, their colonists.

There were also some Acarnanians paid to serve, although they came chiefly for love of Demosthenes and out of goodwill to the Athenians whose allies they were. These all lived on the Hellenic side of the Ionian gulf.