History of the Peloponnesian War

In this way Corcyra maintained her political existence in the war with Corinth, and the Athenian vessels left the island. This was the first cause of the war that Corinth had against the Athenians, viz. that they had fought against them with the Corcyraeans in time of treaty.

Almost immediately after this, fresh differences arose between the Athenians and Peloponnesians, and contributed their share to the war.

Corinth was forming schemes for retaliation, and Athens suspected her hostility. The Potidaeans, who inhabit the isthmus of Pallene, being a Corinthian colony, but tributary allies of Athens, were ordered to raze the wall looking towards Pallene, to give hostages, to dismiss the Corinthian magistrates, and in future not to receive the persons sent from Corinth annually to succeed them. It was feared that they might be persuaded by Perdiccas and the Corinthians to revolt, and might draw the rest of the allies in the direction of Thrace to revolt with them.

These precautions against the Potidaeans were taken by the Athenians immediately after the battle at Corcyra.

Not only was Corinth at length openly hostile, but Perdiccas, son of Alexander, king of the Macedonians, had from an old friend and ally been made an enemy.