History of the Peloponnesian War

After this the Athenian soldiers, as they entered, went up every one to the wall.

And a few of the Peloponnesians that were of the garrison, made head at first and fought and were some of them slain; but the most of them took their heels, fearing in the night both the enemy that charged them and also the traitors of the Megareans that fought against them, apprehending that all the Megareans in general had betrayed them.

It chanced also that the Athenian herald of his own discretion made proclamation that if any Megarean would take part with the Athenians, he should come and lay down his arms. When the Peloponnesians heard this, they stayed no longer, but seriously believing that they jointly warred upon them, fled into Nisaea.

As soon as it was day, the walls being now taken and the Megareans being in a tumult within the city, they that had treated with the Athenians, and with them the rest, as many as were conscious, said it was fit to have the gates opened and to go out and give the enemy battle.