The siege of Uxellodunum (spring 51 B.C.) was the last attempt by the Gauls to defend a fortified town against a Roman attack during Caesar's Gallic War. After the siege of Limonum and the defeat of the besieging army on the Loire some of the survivors, led by a Senonian named Drapes, escaped to the south.
Drapes, who had been involved in the Gallic revolt since the start, managed to collect together a force of 5,000 men. He also joined up with a Cadurcian called Luterius, who had attempted to attack the Roman Province in southern Gaul during the first Gallic Revolt. Their combined force now headed back towards the Province,
Two Roman armies had been involved in the victory at Limonum. One of those armies – two legions under Caius Caninius Rebilus – followed Drapes and Luterius south in an attempt to stop them raiding the Province. When they realised that a Roman army was on their tail, Drapes and Luterius took refuge in Uxellodunum, a Cadurcian town that had once been controlled by Luterius (close to modern Puy D'Issolu on the River Dordogne).
Uxellodunum was a strong defensive position. The town was built on a rocky hill, which protected it against being stormed or surprised. The town was almost surrounded by a bend in the River Dordogne, which ran close to the foot of the hill it was built on. The open side of the town was only three hundred feet wide. Not only was this approach also protected by crags, it also contained a natural spring that provided the garrison with an apparently secure water supply. When Caninius reached the town he realised that he didn't have enough men to quickly begin a regular siege, and so he placed his two legions and their auxiliaries in three camps on some nearby high ground, and prepared to slowly extend his lines around the town.
Drapes and Luterius didn’t play a major part in the siege. The inhabitants of Uxellodunum were naturally worried that they would run out of supplies. Luterius, who had been present at the siege of Alesia, shared this concern, and so the two Gallic leaders set out on a foraging expedition which ended in disaster. At first things went well, and the Gauls were able to gather a large amount of corn. They were then faced with the problem of getting it past the Roman blockade. Their solution was to split their raiding force in half. Drapes, with half of the army, would defend their camp, which was ten miles from the town, while Luterius took a convoy of supplies into the town.
After this everything went wrong for the Gauls. Luterius's convoy was found by the Romans and attacked at dawn by several cohorts of infantry. The people carrying the supplies fled back towards Luterius and his men, who were overwhelmed by the Romans. Luterius himself escaped from the disaster, but instead of attempting to rejoin Drapes or reach the town fled from the area. He was later captured and delivered to the Romans.
Caninius's next move was to attack Drapes' camp with one of his two legions, his cavalry and his German auxiliaries (infantry and cavalry). Drapes had camped near the banks of a river. Caninius's German cavalry found the camp first, and attacked without waiting for the rest of the force to catch up. Caninius formed his legion into their order of battle, and advanced to a position just behind the high ground that surrounded the Gallic camp. When they were all in place the Romans simultaneously advanced onto the high ground, trapping the Gauls against the river. Caught between the Germans, the Romans and the river the entire Gallic force was either killed or captured. Drapes was amongst the prisoners. Towards the end of the siege he starved himself to death, possibly to avoid a worse punishment at Caesar's hands.
On the following day Caninius was joined by Caius Fabius, the victor of the battle on the Loire, with twenty five cohorts of infantry (two and a half legions). This gave the Romans four and a half legions, enough men to construct regular siege works and begin a proper blockade of the town.
While this had been going on Caesar had been travelling through the lands of the Belgae and central Gaul, eventually reaching the Carnutes. Here a number of letters from Caninius caught up with him. Although it was clear that Caninius would have been able to complete the siege without further assistance Caesar decided to take personal command of the operations. Caesar was determined to make an example of the defenders of Uxellodunum. His command in Gaul was due to expire in the following summer, and he wanted to make sure that a fresh revolt wouldn't break out as soon as he left.
On his arrival at Uxellodunum Caesar realised that he would have to attack the town's water supplies. The defenders of Uxellodunum were getting their water from two sources. Some was coming directly from the river, but this involved a dangerous journey down the hillside on one of a limited number of possible routes. Caesar placed archers, slingers and even siege engines opposite each of these routes, and this source of water was cut off.
The second source of water was the spring on the side of the town that faced away from the river. This spring emerged high on the hillside, and had been safe from Roman missile fire. Caesar decided to make two different attempts to cut off this final water supply. The most visible was a giant mound, sixty feet high, with a ten storey high tower on top. From the top of this tower the Romans were able to fire down on the paths that led to the spring, making it much more dangerous for the Gauls to fetch water.
The Gauls responded to this threat by attempting to burn down the tower. Barrels filled with tallow, pitch and dried wood were rolled down the hill onto the Roman works, causing a major fire. At the same time the Gauls attacked the defenders of tower, in an attempt to prevent them from putting out the fires. Caesar responded by ordered a fake attack up the slopes of the hill towards the town walls. This forced the Gauls to abandon the attack on the siege works and man the walls, a move which gave the Romans time to put out the fires.
The second attempt to cut off the water supply was made underground, where the Romans built a series of tunnels searching for the source of the spring. Eventually their tunnels cut into what they described as 'the veins of the spring', and the water dried up. The defenders were already suffering from a severe lack of water. This final blow was too much for them and the defenders of Uxellodunum surrendered.
Caesar decided to make an example of the survivors. Instead of killing them or selling them into slavery he cut of their hands and let them go free. He apparently felt free to act in such a cruel way because he had a reputation for leniency, and so his actions would be understood to be a message and not done from natural cruelty!
After accepting the surrender of Uxellodunum Caesar led two legions into Aquitania, an area he had not yet visited in person. After spending the late summer in Aquitania he visited Narbo in the Roman Province, and then wintered at Nemetocenna in the north-east. Fortunately for Caesar no further revolts broke out, for in the summer his command finally expired. Caesar's political enemies at Rome began to gather, and Caesar was forced to choose between obeying the law by returning to Rome without his legions or risking a civil war. He chose to risk civil war, and on 17 December 50 B.C. Caesar led his legions across the Rubicon, marking the beginning of the Great Roman Civil War.