History of the Peloponnesian War

The Athenians and Peloponnesians had these antecedent grounds of complaint against each other: the complaint of Corinth was that her colony of Potidaea, and Corinthian and Peloponnesian citizens within it, were being besieged; that of Athens against the Peloponnesians that they had incited a town of hers, a member of her alliance and a contributor to her revenue, to revolt, and had come and were openly fighting against her on the side of the Potidaeans. For all this, war had not yet broken out: there was still truce for a while; for this was a private enterprise on the part of Corinth.

But the siege of Potidaea put an end to her inaction; she had men inside it: besides, she feared for the place. Immediately summoning the allies to Lacedaemon, she came and loudly accused Athens of breach of the treaty and aggression on the rights of Peloponnese.

With her, the Aeginetans, formally unrepresented from fear of Athens, in secret proved not the least urgent of the advocates for war, asserting that they had not the independence guaranteed to them by the treaty.