History of the Peloponnesian War

These things against the Potidaeans, the Athenians had precontrived presently after the naval battle fought at Corcyra.

For the Corinthians and they were now manifestly at difference; and Perdiccas, who before had been their confederate and friend, now warred upon them.

And the cause why he did so was that when his brother Philip and Derdas joined in arms against him, the Athenians had made a league with them.

And therefore being afraid, he both sent to Lacedaemon to negotiate the Peloponnesian war and also reconciled himself to the Corinthians the better to procure the revolt of Potidaea.