History of the Peloponnesian War

These were the quarrels between the Peloponnesians and the Athenians. The Corinthians quarrelled the Athenians for besieging Potidaea and in it the men of Corinth and Peloponnesus. The Athenians quarrelled the Peloponnesians for causing their confederate and tributary city to revolt, and for that they had come thither and openly fought against them in the behalf of Potidaea. Nevertheless the war brake not openly forth as yet, and they yet abstained from arms; for this was but a particular action of the Corinthians.

But when Potidaea was once besieged, both for their men's sakes that were within and also for fear to lose the place they could no longer hold. But out of hand they procured of their confederates to go to Lacedaemon; and thither also they went themselves with clamours and accusations against the Athenians that they had broken the league and wronged the Peloponnesians.