History of the Peloponnesian War

After the concluding of the fifty years' peace and the league which followed, and when those ambassadors which were sent for out of the rest of Peloponnesus to accept the said peace were departed from Lacedaemon, the Corinthians (the rest going all to their own cities), turning first to Argos, entered into treaty with some of the Argive magistrates to this purpose:

that the Lacedaemonians having made a peace and league with the Athenians, their hitherto mortal enemies, tending not to the benefit, but to the enslaving of Peloponnesus, it behoved them to consider of a course for the safety of the same, and to make a decree that any city of the Grecians that would, and were a free city, and admitted the like and equal trials of judgment with theirs, might make a league with the Argives for the one mutually to aid the other; and to assign them a few men, with absolute authority from the state, to treat with; and that it should not be motioned to the people, to the end that, if the multitude would not agree to it, it might be unknown that ever they had made such a motion; affirming that many would come into this confederacy upon hatred to the Lacedaemonians.

And the Corinthians, when they had made this overture, went home.

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.