The Mantineans and their allies were the first to come over through fear of the Lacedaemonians. Having taken advantage of the war against Athens to reduce a large part of Arcadia into subjection, they thought that Lacedaemon would not leave them undisturbed in their conquests, now that she had leisure to interfere, and consequently gladly turned to a powerful city like Argos, the historical enemy of the Lacedaemonians, and a sister democracy. Upon the defection of Mantinea, the rest of Peloponnese at once began to agitate the propriety of following her example, conceiving that the Mantineans not have changed sides without good reason; besides which they were angry with Lacedaemon among other reasons for having inserted in the treaty with Athens that it should be consistent with their oaths for both parties, Lacedaemonians and Athenians, to add to or take away from it according to their discretion. It was this clause that was the real origin of the panic in Peloponnese, by exciting suspicions of a Lacedaemonian and Athenian combination against their liberties:
any alteration should properly have been made conditional upon the consent of the whole body of the allies. With these apprehensions there was a very general desire in each state to place itself in alliance with Argos.
In the meantime the Lacedaemonians perceiving the agitation going on in Peloponnese, and that Corinth was the author of it and was herself about to enter into alliance with the Argives, sent ambassadors thither in the hope of preventing what was in contemplation. They accused her of having brought it all about, and told her that she could not desert Lacedaemon and become the ally of Argos, without adding violation of her oaths to the crime which she had already committed in not accepting the treaty with Athens, when it had been expressly agreed that the decision of the majority of the allies should be binding, unless the gods or heroes stood in the way. Corinth in her answer, delivered before those of her allies who had like her refused to accept the treaty, and whom she had previously invited to attend, refrained from openly stating the injuries she complained of, such as the non-recovery of Sollium or Anactorium from the Athenians, or any other point in which she thought she had been prejudiced, but took shelter under the pretext that she could not give up her Thracian allies, to whom her separate individual security had been given, when they first rebelled with Potidaea, as well as upon subsequent occasions. She denied, therefore, that she committed any violation of her oaths to the allies in not entering into the treaty with Athens; having sworn upon the faith of the gods to her Thracian friends, she could not honestly give them up. Besides, the expression was, "unless the gods or heroes stand in the way."Now here, as it appeared to her, the gods stood in the way. This was what she said on the subject of her former oaths. As to the Argive alliance, she would confer with her friends and do whatever was right.
The Lacedaemonian envoys returning home, some Argive ambassadors who happened to be in Corinth pressed her to conclude the alliance without further delay, but were told to attend at the next congress to be held at Corinth.
Immediately afterwards an Elean embassy arrived, and first making an alliance with Corinth went on from thence to Argos, according to their instructions, and became allies of the Argives, their country being just then at enmity with Lacedaemon and Lepreum. Some time back there had been a war between the Lepreans and some of the Arcadians;and the Eleans being called in by the former with the offer of half their lands, had put an end to the war, and leaving the land in the hands of its Leprean occupiers had imposed upon them the tribute of a talent to the Olympian Zeus. Till the Attic war this tribute was paid by the Lepreans, who then took the war as an excuse for no longer doing so, and upon the Eleans using force appealed to Lacedaemon.
The case was thus submitted to her arbitrament; but the Eleans, suspecting the fairness of the tribunal, renounced the reference and laid waste the Leprean territory. The Lacedaemonians nevertheless decided that the Lepreans were independent and the Eleans aggressors, and as the latter did not abide by the arbitration, sent a garrison of heavy infantry into Lepreum. Upon this the Eleans, holding that Lacedaemon had received one of their rebel subjects, put forward the convention providing that each confederate should come out of the Attic war in possession of what he had when he went into it, and considering that justice had not been done them went over to the Argives, and now made the alliance through their ambassadors, who had been instructed for that purpose. Immediately after them the Corinthians and the Thracian Chalcidians became allies of Argos.
Meanwhile the Boeotians and Megarians, who acted together, remained quiet, being left to do as they pleased by Lacedaemon, and thinking that the Argive democracy would not suit so well with their aristocratic government as the Lacedaemonian constitution.