History of the Peloponnesian War

These men of Argos having heard them and reported their proposition both to the magistrates and to the people, the Argives ordered the same accordingly and elected twelve men with whom it should be lawful for any Grecian to make the league that would, except the Lacedaemonians and Athenians, with neither of which they were to enter into any league without the consent of the Argive people.

And this the Argives did the more willingly admit, as well for that they saw the Lacedaemonians would make war upon them (for the truce between them was now upon expiring), as also because they hoped to have the principality of Peloponnesus. For about this time Lacedaemon had but a bad report and was in contempt for the losses it had received. And the Argives in all points were in good estate, as not having concurred in the Attic war, but rather been at peace with both, and thereby gotten in their revenue.

Thus the Argives received into league all such Grecians as came unto them.