Having humbled the Helvetii and firmly entrenched himself in Gaul, Julius Caesar turns his attention to the invading Suebi. These Germans have also observed that Gaul, divided as it is, is ripe for invasion, and have made multiple attempts, including a full-blown attempt at subjugation, to invade the region. Julius Caesar has already smashed them in a previous year's campaign. Now he intends to punish them by pushing into Germania across the Rhine, plundering and burning as he goes. It serves some military purpose perhaps, but the main attraction may be that this makes him the first Roman to cross the Rhine river at the head of an army.
The Germans, however, are smart enough to know not to challenge him in open battle. They abandon their villages and pull back deep into Germania where a large army is mustering. Caesar, frustrated, is forced to pull back without achieving much. As he heads back towards a bridge his legionaries have built specially for the occasion as a way to show off their engineering prowess, he finds himself being attacked from three sides. The Germans have decided to make one last attempt to harry him as he retreats back to safety, and they have targeted the Roman supply column. If it falls, Caesar may starve on his way back to Gaul, and will be forced to beg his Gallic 'allies' for supplies that may not come if the Gauls decide his position looks weak enough. The stakes are high. Battle is imminent.