History of the Peloponnesian War

The same summer, the Megareans in the city, pressed at once by the hostilities of the Athenians, who always invaded their country in full force twice a year, and by their own exiles in Pegae, who had been expelled during the strife of factions by the popular party, and harassed them by their forays, began to discuss amongst themselves the propriety of receiving back their exiles, and not ruining the city in both ways.

The friends of the banished, when aware of such discussion, themselves begged them more openly than before to adopt this proposal.

But the leaders of the commons, knowing that the populace would not be able under the pressure of their sufferings to hold out with them, in their fear entered into communication with the Athenian generals, Hippocrates son of Ariphron, and Demosthenes son of Alcisthenes, wishing to betray the city to them, and thinking that the danger to themselves would be less than from the return of those who had been banished by them. It was agreed then that in the first place the Athenians should take the long walls, (they were about eight stades in length, from the city to Nisaea their port,) that the Peloponnesians might not come to the rescue from Nisaea, where they alone formed the garrison to secure the good faith of Megara; and then that they should endeavour to put the upper town into their hands: and they thought the inhabitants would the more readily surrender when that had been done.