History of the Peloponnesian War
Thucydides
Thucydides. The history of the Peloponnesian War, Volume 1-2. Dale, Henry, translator. London: Heinemann and Henry G. Bohn, 1851-1852.
For in all probability we shall find great want of watchfulness, as is usual on the part of men who have but recently taken possession of a city. By sea, indeed, where they have no thought of any enemy attacking them, and where our strength mainly lies, this will be altogether the case; and even their land-forces are likely to be dispersed through the houses too carelessly.
If then we were to fall upon them suddenly and in the night, I hope that with the aid of those in the city, (if, indeed, there be any one left who wishes us well,) [*]( Or more literally, our measures might be achieved. ) possession of the place might be gained.
And let us not shrink from the danger, but consider that the proverbialsurprises of warare nothing else than chances such as this; which if any one should guard against in his own case, and avail himself of them, when he saw them in the case of his enemy, he would be a most successful general.