In their speech dissuading the Athenians from the Corcyraean alliance the Corinthians are represented by Thucydides (1, 40,5) as saying:

The significance of this passage for Corinthian policy has often been noted, but its bearing on that of Sparta seems to have been ignored. The occasion to which allusion is made is evidently a formal congress of the Peloponnesian League; the language is explicit—the Peloponnesian cities are divided in their vote, Corinth does not record her vote against Athens, but speaks on her behalf. From the detailed account of the preliminaries of the Peloponnesian war we know the procedure of the League. A complainant first applied to Sparta (1, 67), the Spartan assembly voted (1, 87), and if its vote were favourable, the Spartan government summoned a congress of the allies (1, 119), whose vote was taken (1, 125). If this vote were also favourable, the League took action. The machinery was evidently so designed that Sparta could not be committed to a war without her prior consent, nor could she commit the League to a war without the agreement of the majority of its members.