C. Julius Caesar, Gallic War

Caesar, on observing these movements, sends Labienus with six cohorts to relieve his distressed soldiers: he orders him, if he should be unable to withstand them, to draw off the cohorts and make a sally; but not to do this except through necessity. He himself goes to the rest, and exhorts them not to succumb to the toil; he shows them that the fruits of all former engagements depend on that day and hour. The Gauls within, despairing of forcing the fortifications in the plains on account of the greatness of the works, attempt the places precipitous in ascent: hither they bring the engines which they had prepared; by the immense number of their missiles they dislodge the defenders from the turrets: they fill the ditches with clay and hurdles, then clear the way; they tear down the rampart and breast-work with hooks.