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 would 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.