History of the Peloponnesian War

Immediately after this the following events also occurred, which caused differences between the Athenians and the Peloponnesians and led to the war.

While the Corinthians were devising how they should take vengeance on the Athenians, the latter, suspecting their enmity, required of the Potidaeans (who dwell on the isthmus of Pallene and are colonists of the Corinthians but tributary allies of the Athenians), to pull down their wall on the side of Pallene and give hostages, and, furthermore, to send away and not receive in the future the magistrates whom the Corinthians were accustomed to send every year. For they were afraid that the Potidaeans, persuaded by Perdiccas' and the Corinthians, would revolt and cause the rest of the allies in Thrace to revolt with them.