Meanwhile the Potidaeans sent envoys to Athens on the chance of persuading them to take no new steps in their matters; they also went to Lacedaemon with the Corinthians to secure support in case of need. Failing after prolonged negotiation to obtain anything satisfactory from the Athenians; being unable, for all they could say, to prevent the vessels that were destined for Macedonia from also sailing against them; and receiving from the Lacedaemonian government a promise to invade Attica, if the Athenians should attack Potidaea, the Potidaeans, thus favoured by the moment, at last entered into league with the Chalcidians and Bottiaeans, and revolted. And Perdiccas induced the Chalcidians to abandon and demolish their towns on the seaboard and, settling inland at Olynthus, to make that one city a strong place: meanwhile to those who followed his advice he gave a part of his territory in Mygdonia round Lake Bolbe as a place of abode while the war against the Athenians should last. They accordingly demolished their towns, removed inland and prepared for war. 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. They arrived in Macedonia first, and found the force of a thousand men that had been first sent out, just become masters of Therme and besieging Pydna. Accordingly they also joined in the investment, and besieged Pydna for a while. Subsequently they came to terms and concluded a forced alliance with Perdiccas, hastened by the calls of Potidaea and by the arrival of Aristeus at that place. They withdrew from Macedonia, going to Beroea and thence to Strepsa, and, after a futile attempt on the latter place, they pursued by land their march to Potidaea with three thousand heavy infantry of their own citizens, besides a number of their allies, and six hundred Macedonian horsemen, the followers of Philip and Pausanias. With these sailed seventy ships along the coast. Advancing by short marches, on the third day they arrived at Gigonus, where they encamped.