The wall on the side of the isthmus had now works at once raised against it, and manned by the Athenians. That on the side of Pallene had no works raised against it. They did not think themselves strong enough at once to keep a garrison in the isthmus, and to cross over to Pallene and raise works there; they were afraid that the Potidaeans and their allies might take advantage of their division to attack them. Meanwhile the Athenians at home learning that there were no works at Pallene, sometime afterwards sent off sixteen hundred heavy infantry of their own citizens under the command of Phormio, son of Asopius. Arrived at Pallene, he fixed his headquarters at Aphytis, and led his army against Potidaea by short marches, ravaging the country as he advanced. No one venturing to meet him in the field, he raised works against the wall on the side of Pallene. So at length Potidaea was strongly invested on either side, and from the sea by the ships cooperating in the blockade.