History of the Peloponnesian War

The Argive magistrates, on hearing the proposals, reported them to their government and people, and the Argives passed the decree and chose twelve men with whom any of the Hellenes who pleased might conclude an alliance, except the Athenians and the Lacedaemonians; neither of these should be allowed to make a treaty with Argos without the express consent of the Argive people.

These proposals the Argives accepted the more readily, in the first place because they saw that they should have war with the Lacedaemonians—for the treaty with them was on the point of expiring—and, moreover, because they had hoped to secure the hegemony of the Peloponnesus. For at this time Lacedaemon had fallen into very ill repute and was despised on account of its misfortunes, while the Argives had attained an excellent position in all respects, having had no part of the burden of the war with Athens, but rather, as they were at peace with both parties, having reaped a harvest from it.

Thus the Argives were ready to receive into their alliance any of the Hellenes that were so inclined.