History of the Peloponnesian War

Presently upon this the Athenians raised a wall before the city on the part toward the isthmus which they kept with a garrison, but the part to Pallene-ward they left unwalled. For they thought themselves too small a number both to keep a guard in the isthmus and withal to go over and fortify in Pallene, fearing lest the Potidaeans and their confederates should assault them when divided.

When the people of Athens understood that Potidaea was unwalled on the part toward Pallene, not long after they sent thither sixteen hundred men of arms under the conduct of Phormio the son of Asopius, who arriving in Pallene left his galleys at Aphytis, and marching easily to Potidaea wasted the territory as he passed through. And when none came out to give him battle, he raised a wall before the city on that part also that looketh towards Pallene.

Thus was Potidaea on both sides strongly besieged, and also from the sea by the Athenian galleys that came up and rode before it.

Aristeus, seeing the city enclosed on every side and without hope of safety save what might come from Peloponnesus or some other unexpected way, gave advice to all but five hundred, taking the opportunity of a wind, to go out by sea that the provision might the longer hold out for the rest, and of them that should remain within offered himself to be one.

But when his counsel took not place, being desirous to settle their business and make the best of their affairs abroad, he got out by sea unseen of the Athenian guard, and staying amongst the Chalcideans, amongst other actions of the war, laid an ambush before Sermylius and slew many of that city and solicited the sending of aid from Peloponnesus. And Phormio, after the siege laid to Potidaea, having with him his sixteen hundred men of arms, wasted the territory of the Chalcideans and Bottiaeans, and some small towns he took in.