C. Julius Caesar, Gallic War

While he was considering these things an opportunity of acting successfully seemed to offer. For, when he had come into the smaller camp for the purpose of securing the works, he noticed that the hill in the possession of the enemy was stripped of men, although, on the former days, it could scarcely be seen on account of the numbers on it. Being astonished, he inquires the reason of it from the deserters, a great number of whom flocked to him daily. They all concurred in asserting, what Caesar himself had already ascertained by his scouts, that the back of that hill was almost level; but likewise woody and narrow, by which there was a pass to the other side of the town; that they had serious apprehensions for this place, and had no other idea, on the occupation of one hill by the Romans, than that, if they should lose the other, they would be almost surrounded, and cut off from all egress and foraging; that they were all summoned by Vercingetorix to fortify this place.