History of the Peloponnesian War

Afterwards, when the Athenians at home learned that Pallene was not blockaded, they sent sixteen hundred of their own hoplites under the command of Phormio son of Asopius; and he, when he arrived at Pallene, making Aphytis his base, brought his army to Potidaea, marching leisurely and ravaging the country at the same time. And as no one came out against him to give battle he built a wall to blockade the Pallene wall.

And so Potidaea was at length in a state of siege, which was prosecuted vigorously on both sides of it as well as by sea, where a fleet blockaded it.

As for Aristeus, now that Potidaea was cut off by the blockade and he had no hope of saving it unless help should come from the Peloponnesus or something else should happen beyond his expectation, he advised all the garrison except five hundred men to wait for a wind and sail out of the harbour, that the food might hold out longer, and he himself was ready to be one of those who should remain. But since he could not gain their consent, wishing to do the next best thing and to provide that their affairs outside should be put into the best possible condition, he sailed out, unobserved by the Athenian guard.

He then remained among the Chalcidians, whom he assisted generally in carrying on the war, and especially by destroying a large force of Sermylians, whom he ambushed near their city; and meanwhile he kept up negotiations with the Peloponnesians to see if some aid could not be obtained. Phormio, however, after the investment of Potidaea was complete, took his sixteen hundred troops and ravaged Chalcidice and Bottice; and he also captured some towns.

As between the Athenians and the Peloponnesians, then, these additional grounds of complaint had arisen on either side, the Corinthians being aggrieved because the Athenians were besieging Potidaea, a colony of theirs with men in it from Corinth and the Peloponnesus, the Athenians, because the Peloponnesians had brought about the revolt of a city that was an ally and tributary of theirs, and then had come and openly fought with the Potidaeans against themselves. As yet, however, the war had not openly broken out, but there was still a truce for in these things the Corinthians had acted only on their own authority.