Suppressing Gallic rebellionsSens, France
The winter uprising of 54 BC had been a fiasco for the Romans. One legion had been lost entirely, and another almost destroyed. The revolts had shown the Romans were not truly in command of Gaul. Caesar set out on a campaign to subjugate the Gauls completely and forestall future resistance. Down to seven legions, he needed more men. Two more legions were recruited, and one was borrowed from Pompey. The Romans now had 40,000–50,000 men. Caesar began the brutal campaign early, before the weather had warmed. He focused on a non-traditional campaign, demoralizing populations and attacking civilians. He assaulted the Nervii and focused his energy on raiding, burning villages, stealing livestock, and taking prisoners. This strategy worked, and the Nervii promptly surrendered. The legions returned to their wintering spots until the campaign season started fully. Once the weather warmed, Caesar pulled a surprise attack on the Senones. Having had no time to prepare for a siege or even withdraw to their oppidum, the Senones also surrendered. Attention turned to the Menapii, where Caesar followed the same strategy of raiding he had used on the Nervii. It worked just as well on the Menapii, who surrendered quickly.
Caesar's legions had been split up to put down more tribes, and his lieutenant Titus Labienus had with him 25 cohorts (about 12,000 men) and a good deal of cavalry in the lands of the Treveri (led by Indutiomarus). The Germanic tribes had promised aid to the Treveri, and Labienus realized that his relatively small force would be at a serious disadvantage. Thus, he sought to bait the Treveri into an attack on his terms. He did so by feinting a withdrawal, and the Treveri took the bait. However, Labienus had made sure to feint up a hill, requiring the Treveri to run up it, so by the time they reached the top, they were exhausted. Labienus dropped the pretense of withdrawing and gave battle defeating the Treveri in minutes; the tribe surrendered shortly after. In the rest of Belgium, three legions raided the remaining tribes and forced widespread surrender, including the Eburones under Ambiorix.
Caesar now sought to punish the Germanic tribes for daring to help the Gauls. He took his legions over the Rhine once more by building a bridge. But again, Caesar's supplies failed him, forcing him to withdraw to avoid engaging with the still mighty Suebi while short on supplies. Regardless, Caesar had exacted widespread surrender through a vicious retaliatory campaign that focused on destruction over battle. Northern Gaul was essentially flattened. At the end of the year, six legions were wintered, two each on the lands of the Senones, the Treveri, and the Lingones. Caesar aimed to prevent a repeat of the previous disastrous winter, but given the brutality of Caesar's actions that year, an uprising could not be stopped by garrisons alone.