History of the Peloponnesian War

The Athenian generals, finding that some obstacle had arisen, and that they would not be able to take the city by force, immediately proceeded to invest Nisaea; thinking that if they could take it before it was relieved, Megara also would the more quickly surrender.

Now iron, stone-masons. and all other requisites were quickly brought from Athens. So they began from the wall which they occupied, and built a cross-wall on the side of Megara, from the point mentioned down to the sea on each side of Nisaea; the whole army having divided amongst themselves the trench and walls; and they used the stones and bricks from the suburb, and cutting down the fruit trees and timber, strengthened with a palisade whatever point might require it. The houses, too, in the suburb, when provided with battlements, were in themselves a fortification. That whole day they continued working;

and about afternoon of the next day the wall was all but completed, when the garrison in Nisaea, in despair of provisions, (for they used to receive daily rations from the upper city,) not thinking that the Peloponnesians would soon relieve them, and supposing the Megareans to be their enemies, capitulated to the Athenians, on condition that after surrendering their arms they should each be ransomed for a stipulated sum; but that the Lacedaemonians, both the commander and all others in the place, should be treated by the Athenians according to their pleasure. On these conditions they surrendered and went out;

and the Athenians, having broken down the long walls at their abutment on Megara, and having taken possession of Nisaea, proceeded with their other preparations.