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.