History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
He so stationed the youngest of his troops that they might dash out against the enemy, in case they attacked at any point, and proposed to take himself three hundred picked men and, bringing up the rear, to make a stand and beat off the foremost of the enemy whenever they pressed him hard.
And before the enemy were near he exhorted his soldiers, so far as haste allowed, in the following words: