History of the Peloponnesian War

The persons with whom they had communicated reported the proposal to their government and people, and the Argives passed the decree and chose twelve men to negotiate an alliance for any Hellenic state that wished it, except Athens and Lacedaemon, neither of which should be able to join without reference to the Argive people.

Argos came in to the plan the more readily because she saw that war with Lacedaemon was inevitable, the truce being on the point of expiring; and also because she hoped to gain the supremacy of Peloponnese. For at this time Lacedaemon had sunk very low in public estimation because of her disasters, while the Argives were in a most flourishing condition, having taken no part in the Attic war, but having on the contrary profited largely by their neutrality.

The Argives accordingly prepared to receive into alliance any of the Hellenes that desired it.