After Fighting Helvetii and Germans, Caesar Faces the Belgae:
In 57 B.C., the Battle of Sabis, which is also called the Battle of Sambre (or the Sambre River), was the major confrontation between Caesar and the Belgae. Caesar nearly lost, and in the aftermath, he showed he could be merciless if betrayed.
Following victories at Bibracte and Vosges in the campaigning year of 58, Caesar, stationed in Gaul as proconsul, raised two more legions, the 13th and 14th, doubling what he had started with.
Seeing Caesar wasn't leaving soon, Belgic tribes in northern Gaul formed a confederacy against Rome. Caesar says he was called on to protect one Belgic tribe, the Remi, from the others.
The Remi, Caesar, and Bibrax:
The Remi tribe gave all Caesar asked of them, including information on the other Belgae tribes, food and supplies, hostages, and obedience. Chiefly, the Remi were concerned about the Suessiones led by King Galba, since they were their closest neighbors. Caesar led his men and pitched camp at the edge of Remi territory, by the Aisne (Axona) river. Eight miles from there the Belgae had begun to attack a Remi town named Bibrax. The Remi were overwhelmed until Caesar sent help. Then the Belgae decided it best to leave Bibrax and go after Caesar at the Aisne river, instead, laying waste to Remi territory on their way.
Aisne:
The Belgic forces were formidable, so Caesar didn't immediately engage them in battle, but there were skirmishes. The Romans were able to throw the tribes into confusion with cavalry, light troops, and Numidian archers. The Belgae decided to go home and left in great confusion, but believing the Romans too afraid for a proper battle.
The next day Caesar entered Noviodumun in Suessiones territory. His siege towers terrified the Gauls, leading them to surrender. Next, the Bellovaci surrendered. These two tribes were spoken for by Gallic allies of Rome, the Remi and Diviaticus.
The Battle of the Sabis or Sambre:
The Nervii were the largest remaining hostile tribe. They were stationed with the Trebates, Viromandui on the far side of the Sabis river. They were expecting the Atuabantes. Both sides had informants, so the Nervii knew how the Romans traveled. The Romans were vulnerable while on the march. The Nervii gave evidence that they would challenge Caesar's crossing, so Caesar rearranged his troops so that experienced legions would be together; the baggage and the two new legions apart. When they stopped, most of the men worked on the campsite so it could be done as quickly as possible. This left the Romans unarmed.
The Nervii Attack:
As soon as the Nervii sighted the baggage trains, they rushed from their hiding places, routed the Roman cavalry and then attacked the men working on building the camp. There was no time for the Romans to prepare for battle. Instead, the leaders gathered together those men who were nearest. Caesar ordered the 10th Legion to charge and so halt the Atrebantes. Other legions were making headway against the Viromandui, but most of the Nervii were on the Roman right flank, where the Romans were not holding their own. Caesar grabbed a shield and ran up to the front line, yelling encouragement to his men.
The Battle Turns:
While Caesar inspired the fighters, it was another event that turned the tide and let the Romans win. The Nervii caught site of the two new legions who had been behind the baggage train. They were still fresh, encouraging to Romans and discouraging to battle-weary Belgians. The 10th legion went after the Nervii from their rear and the new legions joined the fighting. The Nervii continued to fight for a long time. When they surrendered, Caesar ordered them to stay within their own territories.
The Atuatuci:
The Atuatuci had been expected by the Nervii, but had not shown up. After the defeat at the Sabis river, they determined to resist the Romans. When the Romans arrived, they built a ditch and rampart around the Atuatuci walls, which prevented those inside from getting out. The Atuatuci were dismayed only when they saw the Roman siege engines. They surrendered and were told to throw out all their weapons. They threw out an immense number, but at night some of them took up still hidden ones and charged. The next day Caesar held the entire people responsible and the entire population of 53,000 were sold as slaves.
Sources:
An English translation of De bello Gallico, Caesar's Gallic Wars.
Adrian Goldsworthy's Life of a Colossus
"Two Caesarian Battle-Descriptions: A Study in Contrast," by Robert D. Brown. The Classical Journal, Vol. 94, No. 4. (Apr. - May, 1999), pp. 329-357.
