C. Julius Caesar, Gallic War

Caesar, after he came from the territories of the Menapii into those of the Treviri , resolved for two reasons to cross the Rhine ; one of which was, because they had sent assistance to the Treviri against him; the other, that Ambiorix might not have a retreat among them. Having determined on these matters, he began to build a bridge a little above that place where he had before conveyed over his army. The plan having been known and laid down, the work is accomplished in a few days by the great exertion of the soldiers. Having left a strong guard at the bridge on the side of the Treviri , lest any commotion should suddenly arise among them, he leads over the rest of the forces and the cavalry. The Ubii, who before had sent hostages and come to a capitulation, send embassadors to him, for the purpose of vindicating themselves, to assure him that "neither had auxiliaries been sent to the Treviri from their state, nor had they violated their allegiance;" they entreat and beseech him "to spare them, lest, in his common hatred of the Germans, the innocent should suffer the penalty of the guilty: they promise to give more hostages, if he desire them." Having investigated the case, Caesar finds that the auxiliaries had been sent by the Suevi; he accepts the apology of the Ubii, and makes the minute inquiries concerning the approaches and the routes to the territories of the Suevi.