de bello gallico, 5.45

By as much as the attack was daily more serious and bitter, and especially because, with a great number of the soldiers having been exhausted by their wounds, the matter had come to a scarcity of defenders, by so much were more frequent letters and messengers sent to Caesar; a part of which, having been captured, were killed with torture in the sight of our soldiers. There was within our camp one Nervian, by name Vertico, born in a distinguished position, who from the beginning of the blockade had deserted to Cicero, and had exhibited his fidelity to him. This man persuades his slave, by the hope of freedom and great rewards, to carry a letter to Caesar. That man carries these out tied onto his javelin, and, a Gaul having moved about among the Gauls without any suspicion, he reached Caesar. From him it is learned about the dangers of Cicero and the legion.