Caesar wins his first military conflict in Gaul in 58 B.C. and sends all the belligerents back home with minor punishments.
After seeing the Romans build a bridge in one day over a river that took them twenty days to cross, the Helvetii fled from the Romans. In pursuit, Caesar faced two obstacles.
First, he sent ahead an auxiliary force of 4,000 Aedui cavalry led by Dumnorix, the Aeduian nobleman. Dumnorix encroached upon the Helvetii too close, engaged in a skirmish and lost, embarrassing the Roman name with a cowardly flight while further emboldening the Helvetii.
Secondly, the Aedui repeatedly failed to deliver the food supplies they promised, giving false reasons for delay. The Gallic leaders in Caesar’s camp soon revealed that the cause of these burdens was Dumnorix, the ambitious Aeduian who sought to lord over the Aedui himself.
Dumnorix’s brother, Diviciacus, was the rightful king of the Aedui at the time. He had been a close friend and ally to Caesar and Rome. By supporting the Helvetii efforts to conquer Gaul and expel the Romans, Dumnorix saw an opportunity to seize power away from his brother and put in place a new regime with him in charge. Diviciacus was among those who came to Caesar with the news of this sedition, but was in tears for betraying his brother – ever yet conflicted by the fact his brother was betraying him. Dumnorix had long been currying favor with the populous mass of the Aedui by means of gifts and generosity. Caesar, careful to not embroil himself in foreign family distractions and to maintain his valuable friendship with the otherwise influential Diviciacus, granted Dumnorix the mercy Diviciacus pleaded for while putting a stop to his treachery. He had Dumnorix kept under watch within the Roman camp. From this point on, the Helvetii stopped receiving updates from Dumnorix as to where the Romans were marching.
On the contrary, word came to Caesar that the Helvetii were camped on a mountain eight miles away. Caesar sent his lieutenant-general, Titus Labienus, in charge of all cavalry to the summit of the mountain above the Helvetii camp. However, due to a dwindling food supply, Caesar was forced to pull back and resupply. Some Gallic deserters fled to the Helvetii camp and reported this to the Helvetii. Till then, the Helvetii had been unaware that the Romans were so near and surrounding, but they became emboldened watching the Romans leaving. So, they chased after them, pestering the tail end of the Roman march.
Caesar had enough, turned, and faced for battle. The classic Roman onslaught of javelin throws scattered the Helvetii line and destroyed their shields, making the subsequent charge by Roman sword lethal. The Helvetii retreated a mile back towards their camp up the hill with Romans following in suit. A surprise attack on the Roman’s exposed right flank by some 15,000 Gauls supporting the Helvetii (Boii and Tulingi tribes) inspired the Helvetii to renew their attack. So, Caesar responsively split his army. Two thirds opposed and defeated the returning Helvetii, while the other third wheeled and confronted the surprise attack on their right flank.
Fighting continued well into the night as the Helvetii had nowhere to flee to, no route to rout. They built a makeshift wall out of their carts and supplies up in there camp but to no avail. The Romans entered it, forcing way past these barricades despite incurring some damage, and won, capturing the camp and about 130,000 people, including Helvetii nobles, women, and children. A larger remainder fled and marched north three days yonder toward the border of the Lingones (modern: East-Northeast France). The Romans stayed behind, tended to the wounded, buried the dead, and counted up the spoils won from the Helvetii camp.
Caesar sent a message ahead to the Lingones, the neighboring tribe, that they should not offer any assistance to the Helvetii. Therefore, the Helvetii were compelled to surrender as they had no shelter, no refuge, provisions, nor standing homeland. They sent messengers to Caesar, still three days away, offering their surrender. Caesar replied no answer but for them to wait for his arrival. Once he got there, the Helvetii were forced to surrender their arms, hostages, and slaves.
Aside from a small percentage of prisoners who attempted to run but were rounded up and returned, the Helvetii obeyed Caesar. Some of the Boii tribe were repurposed to settle in Aedui territory upon Aedui request, for the Boii were courageous people and the Aedui saw value in incorporating them into their society as free people. All other participating tribes were ordered to return to their respective homelands. The Allobroges were made to share their foodstuffs for all the tribes temporarily.
As for the Helvetii, they were sent back to the land from whence they came. Here, Caesar displayed great wisdom because the land of the Helvetii was excellently fertile and their absence would leave a vacuum, which Caesar did not want to see the neighboring Germans fill. All this done in short time, Caesar stamped his name on Gaul as a successful military leader with a penchant for peace and compassion toward the greater good of the region, so long as it be under consideration of Caesar, a proxy of Rome.