History of the Peloponnesian War
Thucydides
Thucydides. History of the Peloponnesian War. Crawley, Richard, translator. London and Toronto: J. M. Dent and Sons Ltd.; New York: E. P. Dutton and Co., 1914.
So at length Potidaea was strongly invested on either side, and from the sea by the ships cooperating in the blockade.
Aristeus, seeing its investment complete, and having no hope of its salvation, except in the event of some movement from the Peloponnese, or of some other improbable contingency, advised all except five hundred to watch for a wind, and sail out of the place, in order that their provisions might last the longer. He was willing to be himself one of those who remained. Unable to persuade them, and desirous of acting on the next alternative, and of having things outside in the best posture possible, he eluded the guardships of the Athenians and sailed out.
Remaining among the Chalcidians, he continued to carry on the war; in particular he laid an ambuscade near the city of the Sermylians, and cut off many of them; he also communicated with Peloponnese, and tried to contrive some method by which help might be brought.
Meanwhile, after the completion of the investment of Potidaea, Phormio next employed his sixteen hundred men in ravaging Chalcidice and Bottica: some of the towns also were taken by him.
The Athenians and Peloponnesians had these antecedent grounds of complaint against each other: the complaint of Corinth was that her colony of Potidaea, and Corinthian and Peloponnesian citizens within it, were being besieged; that of Athens against the Peloponnesians that they had incited a town of hers, a member of her alliance and a contributor to her revenue, to revolt, and had come and were openly fighting against her on the side of the Potidaeans. For all this, war had not yet broken out: there was still truce for a while; for this was a private enterprise on the part of Corinth.