The disaster at Atuatuca (October 54 B.C.) was one of the most serious setbacks suffered by Julius Caesar during his conquest of Gaul, and saw the Eburones destroy an entire Roman legion that had just entered winter quarters.
54 B.C. had seen a drought and a poor corn harvest, and so after returning from his second expedition to Britain Caesar was forced to scatter his legions across a wide area of north-eastern Gaul. The newest of his legions, reinforced by five cohorts, under the command of Q. Titurius Sabinus and L. Aurunculeius Cotta, was sent to Atuatuca, in the lands of the Eburones, where they built a fort, met with the local leaders, and prepared for the winter.
Sabinus and Cotta arrived at Atuatuca just before the outbreak of a widespread rebellion, apparently inspired by the Treviri. Fifteen days after the Romans entered their winter quarters, a large force of Eburones surprised a party that was gathering timber, and then attempted to rush the Roman camp.
This attack ended in failure. A force of Spanish cavalry was sent out of the camp, and defeated the Gallic cavalry, while the attack on the foraging party had given the Roman infantry time to man the walls.
The Eburones had two kings – Ambiorix and Cativolcus. Ambiorix, who was leading the attack on the Roman camp, resorted to trickery. He arranged a meeting with two senior Romans – C. Arpincius, a friend of Sabinus and Q. Junius, from Spain, who had met with him before. Ambiorix posed as a friend of Caesar who had been forced to attack the camp against his will as part of a much wider revolt. Not only had every Roman camp been attacked on the same day, but a large force of Germans had already crossed the Rhine and would soon arrive at Atuatuca. Ambiorix suggested that Cotta and Sabinus should abandon their camp, and attempt to reach the winter quarters of either Q. Cicero or Labienus. According to Caesar Ambiorix made an oath to give the Romans safe passage through his lands.
When Arpincius and Junius returned to the Roman camp a council of war was summoned. Most of the officers, including Cotta, wanted to remain in their camp and defend it against the (non-existent) German attack, but Sabinus argued that the Gauls would not have dared attack the camp unless Caesar had already left for Italy and the Germans had crossed the Rhine. After a debate that lasted until midnight Sabinus got his way.
On the following morning the Romans left their camp. Despite the attack on the previous day Sabinus still believed that he could trust Ambiorix, and so his troops set out in a long thin column, with most of their baggage.
Sabinus was wrong. Two miles from the camp the Roman's route would take them through a large valley. Ambiorix had posted his troops on both sides of the valley. Once most of the Romans had entered the valley the Gauls attacked from both sides.
Caesar gives a detailed account of the battle that followed. The Romans formed into a defensive circle (an orbis or globus), and for some time held off the Gauls. Ambiorix ordered his men to pull back, blockage the Romans and only attack with their missile weapons. Whenever the Romans attempted a counterattack the Gauls retreated. After about eight hours of this the Romans were being worn down - Cotta was wounded, and the chief centurion was killed. Sabinus still believed that he could negotiate with Ambiorix, but once again he was mistaken, this time fatally. At about the same time Cotta was killed, as were most of the Roman soldiers. A small party fought its way back to the fort, but with no chance of escape killed themselves in the night.
A handful of survivors escaped through the woods and eventually reached Labienus in his winter quarters, but Caesar had lost nearly a legion and a half, in a disaster that foreshadowed the more famous destruction of the German legions in the Teutoburger Wald just over sixty years later.
The Gauls failed to take advantage of their success. None of the other winter camps fell to them, although Q. Cicero's camp was hard pressed by the Nervii. Caesar had not gone to Italy. He gathered two legions, tricked the besieging Gauls into attacking his camp, and broke through to Cicero's winter quarters. The Gauls abandoned a plan to attack Labienus's camp, and the Romans went back into their winter quarters. The main campaigns against the rebels took place in the following spring and summer.
The site of Atuatuca is unclear. Caesar's own account of the disaster on Book V of his commentary on the war doesn't give any clear location other than to say that it was amongst the lands of the Eburones, most of whom lived between the Meuse and the Rhine. The name Atuatuca is given in the following year when Q. Cicero camped on the same site during the final campaign against Ambiorix, and at this point it is described as being the centre of the lands of the Eburones.
This may exclude the traditional location of Tongeren, which is ten miles short of the Meuse, although the town was later known to the Romans as Atuatuca Tungrorum, and the Meuse does curve around to the west just to the south of Tongeren. Another argument against the identification of Tongeren with this Atuatuca is that in 53 B.C. the camp was raided by Germans who had only recently crossed the Rhine to raid the lands of the Eburones. Given than the Rhine is some eighty miles to the east of Tongeren it would seem most likely that the Roman camp was somewhere to the east of the Meuse.