The thirty ships of the Athenians, arriving before the Thracian places, found Potidaea and the rest in revolt.

Their commanders, considering it to be quite impossible with their present force to carry on war with Perdiccas and with the confederate towns as well turned to Macedonia, their original destination, and, having established themselves there, carried on war in co-operation with Philip, and the brothers of Derdas, who had invaded the country from the interior.
Meanwhile the Corinthians, with Potidaea in revolt and the Athenian ships on the coast of Macedonia, alarmed for the safety of the place and thinking its danger theirs, sent volunteers from Corinth, and mercenaries from the rest of Peloponnese, to the number of sixteen hundred heavy infantry in all, and four hundred light troops.

Aristeus, son of Adimantus, who was always a steady friend to the Potidaeans, took command of the expedition, and it was principally for love of him that most of the men from Corinth volunteered.

They arrived in Thrace forty days after the revolt of Potidaea.
The Athenians also immediately received the news of the revolt of the cities.

On being informed that Aristeus and his reinforcements were on their way, they sent two thousand heavy infantry of their own citizens and forty ships against the places in revolt, under the command of Callias, son of Calliades, and four colleagues.