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 Potidæa 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 Potidæa 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. Meanwhile the Potidæans and the Peloponnesians with Aristeus were encamped on the side looking towards Olynthus on the isthmus, in expectation of the Athenians, and had established their market outside the city. The allies had chosen Aristeus general of all the infantry; while the command of the cavalry was given to Perdiccas, who had at once left the alliance of the Athenians and gone back to that of the Potidæans, having deputed Iolaus as his general: The plan of Aristeus was to keep his own force on the isthmus, and await the attack of the Athenians; leaving the Chalcidians and the allies outside the isthmus, and the two hundred cavalry from Perdiccas in Olynthus to act upon the Athenian rear, on the occasion of their advancing against him; and thus to place the enemy between two fires. While Callias the Athenian general and his colleagues dispatched the Macedonian horse and a few of the allies to Olynthus, to prevent any movement being made from that quarter, the Athenians themselves broke up their camp and marched against Potidæa. After they had arrived at the isthmus, and saw the enemy preparing for battle, they formed against him, and soon afterwards engaged. The wing of Aristeus, with the Corinthians and other picked troops round him, routed the wing opposed to it, and followed for a considerable distance in pursuit. But the rest of the army of the Potidæans and of the Peloponnesians was defeated by the Athenians, and took refuge within the fortifications. Returning from the pursuit, Aristeus perceived the defeat of the rest of the army. Being at a loss which of the two risks to choose, whether to go to Olynthus or to Potidæa, he at last determined to draw his men into as small a space as possible, and force his way with a run into Potidæa.