The Battle of Alesia, also called the Siege of Alesia (September 52 BC), was the most important battle of the Gallic Wars. It took place near the fortified village of Alesia in modern-day France, which was a major settlement of the Mandubii tribe. The Roman army, led by Julius Caesar, fought against a group of Gallic tribes united under the leader Vercingetorix of the Arverni. This was the last major battle between the Gauls and Romans and is seen as one of Caesar's most important victories. It is also a well-known example of siege warfare. The Roman army built two lines of fortifications: one to keep the Gallic forces inside the siege, and another to stop the Gallic relief army from entering. The Battle of Alesia ended Gallic independence in the regions of modern France and Belgium.
Archaeologists and historians believe the battle site was likely located on Mont Auxois, near the town of Alise-Sainte-Reine in France. Caesar himself described the event in his book Commentarii de Bello Gallico. Other ancient writers, such as Plutarch and Cassius Dio, also wrote about it. After the Roman victory, Gaul (roughly modern-day France) was controlled by Rome. However, the northern areas of Gaul would not officially become a Roman province until 27 BCE. The Roman Senate honored Caesar with a thanksgiving celebration lasting 20 days for his success in the Gallic War.
Background
In 58 BC, after serving as consul in 59 BC, Julius Caesar arranged his own appointment as proconsul (governor) of three Roman provinces through the First Triumvirate. These provinces were Cisalpine Gaul (northern Italy), Illyricum (on the eastern coast of the Adriatic Sea), and Gallia Narbonensis (in southeastern France and along the rest of France’s Mediterranean coast). The proconsular term was meant to last one year, but Caesar’s governorship lasted five years, which was unusual. He also commanded four legions.
Caesar led the Gallic Wars (58–50 BC), which resulted in the conquest of Gaul beyond Gallia Narbonensis. When the Helvetii, a group of tribes from what is now Switzerland, planned to move to the Atlantic coast through Gaul, Caesar went to Geneva and stopped them from entering Gaul. While he went to Gallia Cisalpina to gather three more legions, the Helvetii attacked the lands of the Aedui, Ambarri, and Allobroges, three Gallic tribes. These tribes asked Caesar for help. Caesar and his Gallic allies defeated the Helvetii. The Gallic tribes then asked Caesar to help them fight the Suebi, a Germanic tribe. Caesar defeated the Suebi and, to show Roman strength, crossed the Rhine in 55 BC. In 57 BC, he intervened in conflicts among Gallic tribes and marched on the Belgae in northern Gaul. From that time, he conquered the Gallic peoples one by one. His successes in Gaul gave Caesar political influence in Rome and great wealth from war spoils and the sale of captured people as slaves.
Concerns among the Gauls reached a peak in 52 BC, leading to a widespread revolt that the Romans had long feared. The campaigns of 53 BC were especially harsh, and the Gauls worried about their future. Earlier, the Gauls had not been united, which made them easier to conquer. This changed in 53 BC, when Caesar declared that Gaul would now be treated as a Roman province, subject to Roman laws and religion. This caused great concern among the Gauls, who feared the Romans would destroy their sacred lands, which the Carnutes protected. Each year, druids met there to settle disputes between tribes in the area considered the center of Gaul. A threat to their holy lands finally united the Gauls. During the winter, Vercingetorix, the leader of the Arverni tribe, gathered an unusually large group of Gauls to fight together.
Prelude
Caesar was in Rome when he learned about the revolt. He quickly traveled north to stop the revolt from spreading, first going to Provence to protect it, then to Agedincum to face the Gallic forces. Caesar took a long, winding path to reach the Gallic army, capturing several fortified towns to gather supplies. Vercingetorix had to leave his siege of the Boii (a tribe allied with Rome) capital, Gorgobina. However, it was still winter, and Vercingetorix realized Caesar had changed his route because the Romans were running low on supplies. Vercingetorix planned to starve the Romans by avoiding direct attacks and instead raiding groups collecting food and supply trains. He abandoned many fortified towns, choosing to defend only the strongest ones to keep their supplies from falling into Roman hands. Again, Caesar faced a shortage of supplies and decided to besiege the fortified town of Avaricum, where Vercingetorix had retreated.
Vercingetorix had originally wanted to avoid defending Avaricum, but the Bituriges Cubi tribe convinced him otherwise. The Gallic army was camped outside the town. While defending, Vercingetorix wanted to flee and escape the Romans, but the people of Avaricum refused to leave. When Caesar arrived, he immediately began building a defensive structure. The Gauls constantly attacked the Romans and their food-gathering groups while the camp was being built, even trying to set it on fire. Despite the harsh winter weather, the Romans completed a strong camp in 25 days. Siege weapons were built, and Caesar waited for a chance to attack the heavily fortified town. He chose to strike during a rainstorm, when guards were distracted. Siege towers and artillery were used to attack the walls. Eventually, the artillery broke a hole in the wall, and the Gauls could not stop the Romans from taking the town. The Romans looted and destroyed the settlement; Caesar took no prisoners and claimed 40,000 people were killed. The Gallic coalition did not break apart after this defeat, showing Vercingetorix’s strong leadership. Despite this loss, the Aedui tribe decided to rebel and join the coalition, causing another problem for Caesar’s supply lines, as he could no longer get supplies through them (though the capture of Avaricum temporarily provided supplies).
Vercingetorix then moved to Gergovia, the capital of his own tribe, which he wanted to protect. Caesar arrived as the weather improved and food became more available, which helped ease supply problems. As usual, Caesar quickly built a defensive structure for the Romans. He then worked to capture land near the town. The events of the Battle of Gergovia are unclear. Caesar claimed he ordered his men to take a hill near the town and then called for a retreat. However, no retreat happened, and the Romans directly attacked the settlement. Caesar’s claim that he ordered a retreat is likely false, as it may have been his plan all along to attack directly. The Roman attack failed because they were outnumbered. Caesar reported that 700 men died, including 46 centurions, but these numbers may be much lower than the actual count. Caesar withdrew from his siege, and Vercingetorix’s victory brought more tribes to his side. At the same time, the Romans persuaded many Germanic tribes to join their cause.
Vercingetorix led the army he had gathered, mainly cavalry, to stop Caesar. The two sides met in the Battle of the Vingeanne, where Caesar defeated Vercingetorix’s cavalry.
Siege
After his cavalry was defeated, Vercingetorix led his forces toward the fortified hill of Alesia, where a major siege would take place. Following a failed attack at Gergovia, Julius Caesar decided not to attack the Gauls directly. Instead, he chose to surround Alesia and cut off its food supply. Vercingetorix agreed to this plan, hoping to use Alesia as a trap to attack the Romans from both sides. He quickly sent a message asking for help from other tribes. Vercingetorix likely did not expect the strength of the Roman defenses. While modern archaeology suggests Caesar’s preparations were not as complete as he claimed, it is clear that he built strong fortifications. Over one month, about 25 miles of defenses were constructed, including trenches, moats, towers, and traps. The walls were built in two lines: one to protect against the defenders inside Alesia and another to guard against the relief force. Though the lines were not continuous as Caesar described, they used the natural landscape and were effective. The relief force arrived quickly, but attacks by both the defenders and the relief army failed to drive the Romans away.
Alesia was a hilltop fortress with two rivers on either side. Because of its strong position, Caesar decided to surround it and force the defenders to surrender through starvation. With about 80,000 soldiers and civilians inside Alesia, food supplies would run out quickly. To block all escape, Caesar ordered the construction of a large defensive wall, called a contravallation, around the fortress. This wall was 16 kilometers long and had 23 towers. While building the wall, the Gauls attacked with their cavalry to slow progress. Caesar placed his soldiers in front of the camp to protect against enemy attacks and sent his German allies to chase the Gallic cavalry.
Before the main wall was completed, Vercingetorix sent his cavalry to gather other tribes for help. When Caesar learned of this from captured soldiers, he dug a trench 6 meters wide with steep sides and built other defenses 592 meters away. This distance helped protect Roman workers from surprise attacks at night or from enemy weapons. Between the trench and the main wall, Caesar dug two more trenches, filled one with river water, and built a high wooden wall with pointed stakes to stop enemies from climbing. Towers were placed every 24 meters around the defenses.
Some Roman soldiers had to travel far to get wood and grain, which reduced the number of workers. The Gauls attacked the defenses with large groups. To make up for this, Caesar added more traps, such as sharpened stakes in deep pits and hidden pits filled with sharpened poles. These traps were covered with branches to hide them. He also placed iron hooks in the ground to trip attackers.
To prepare for the relief force, Caesar built an outer wall, called a circumvallation, facing the opposite direction. This wall was 20.7 kilometers long and used the best ground available.
Inside Alesia, food supplies ran out quickly. Vercingetorix collected all grain and limited rations. The Gauls decided to send the elderly and sick out of the city, and some families sent their children away, hoping Caesar would take them as captives and feed them. However, Caesar refused to let them enter his camp, leaving them to starve between the walls.
The Gallic relief force arrived and camped on a hill one mile from the Roman defenses. The next day, the Gauls attacked the outer wall, while the defenders inside Alesia attacked the inner wall. The combined attack failed. The next night, the Gauls attacked again, but Roman generals Marc Antony and Caius Trebonius brought reinforcements. When the relief force saw the Romans preparing to attack, they withdrew. The defenders inside Alesia were delayed by having to fill Roman trenches. When they saw their allies retreat, they returned to the city.
The Gauls noticed a weakness in the Roman defenses: the north side of the hill could not be fully enclosed. They placed two Roman legions on difficult ground and attacked there at noon. Vercingetorix led a sally to attack the inner wall. Caesar sent Labienus to help defend the weak spot with six groups of cavalry. He later sent Brutus and Caius Fabius with more cavalry to support the defense. After repelling the attack, Caesar joined the battle with fresh troops. He also sent soldiers to attack the relief force from behind. Labienus was nearly overwhelmed and informed Caesar of his plan to attack.
Aftermath
After crushing the revolt, Caesar ordered his legions to stay in the lands of the defeated tribes during the winter to stop any more rebellions. Troops were also sent to the Remi, who had remained loyal allies to the Romans throughout the campaign. However, resistance was not completely over: southwest Gaul had not yet been pacified.
Alesia was the final major battle where organized Gallic resistance to Caesar's invasion ended, marking the end of the Gallic Wars. In the following year (50 BC), smaller battles were fought to complete the conquest. During the Roman civil wars, Gaul was largely left to manage itself. Marcus Vipsanius Agrippa became its first governor between 39 and 38 BC. In 39 BC, he moved the Ubians to the west bank of the Rhine River, and in 38 BC, he stopped a rebellion in Aquitania. He built a network of roads centered on the Gallic capital, Lugdunum (Lyon). Gaul was divided into three Roman provinces: Gallia Aquitania, Gallia Lugdununensis, and Gallia Belgica. Only the Arverni kept their independence after their victory over Caesar at the Battle of Gergovia.
For Caesar, the Battle of Alesia was a major success, both in war and politics. The Roman Senate declared 20 days of celebration for this victory but, due to political reasons, refused to let Caesar hold a triumphal parade, which was the highest honor for a general. Political tensions grew, and two years later, in 49 BC, Caesar crossed the Rubicon, starting the Roman Civil War (49–45 BC), which he won. After being elected consul each year of the war and serving as a temporary dictator, Caesar was named dictator perpetuus (dictator for life) by the Senate in 44 BC. His increasing power weakened the traditions of the Roman Republic. More civil wars followed after his death. The last war was between Octavian (later Augustus) and Marc Antony over who would rule Rome, which Octavian won. This marked the practical end of the Roman Republic and the start of rule by emperors.
Vercingetorix was captured and held in Rome for five years, waiting for Caesar’s triumph, which was delayed by the civil war. As was traditional, he was displayed during the triumph and then taken to the Tullianum, where he was ritually killed in 46 BC.
The Gallic Wars do not have a clear end date. Roman legions remained active in Gaul through 50 BC, when Aulus Hirtius took over writing Caesar’s reports on the war. Campaigns may have continued if not for the approaching Roman civil war. The legions in Gaul were eventually withdrawn in 50 BC as the civil war neared, because Caesar needed them to fight his enemies in Rome. The Gauls were not fully controlled and were not yet formal parts of the empire. However, Caesar did not complete this task; he left it to his successors. Gaul would not officially become Roman provinces until Augustus ruled in 27 BC. There may have been unrest in the region as late as AD 70.
Importance
Paul K. Davis writes that "Caesar's victory over the combined Gallic forces made sure that Rome had control over Gaul for the next 500 years. Caesar's victory also caused a conflict with the Roman government, which led to his invasion of the Italian peninsula."
Adrian Goldsworthy writes: "Almost all the tribes involved in the rebellion gave up. In many ways, Caesar's final victory was especially important because so many groups had joined together. The Celtic/Gallic people had finally tested the strength of the Roman army and were completely defeated. Almost all of them now understood that they had been conquered."
Identification of the site
For many years, people did not know exactly where the battle took place. Two towns were considered as possible locations: Alaise in the Franche-Comté and Alise-Sainte-Reine in the Côte-d'Or. Emperor Napoleon III of France supported Alise-Sainte-Reine and, in the 1860s, paid for studies that found evidence of Roman camps in the area. He later built a statue to Vercingetorix in the ruins discovered there. Ongoing studies by experts have since confirmed that Alise-Sainte-Reine is most likely the site of the Battle of Alesia. Classical historian and archaeologist Colin Wells stated that excavations in the 1990s at Alise-Sainte-Reine should have removed all uncertainty about the location and called other suggestions for different sites "…passionate nonsense." Other ideas about where the battle happened, which are not supported by most scientists or historical research, include locations like Chaux-des-Crotenay.
Numbers involved
Exact numbers about the size of the armies and the number of people who were hurt are hard to find. These numbers have often been used as a tool for persuasion, which makes them unreliable. In his book De Bello Gallico, Caesar wrote that a Gallic relief force had 250,000 soldiers, but this is likely an exaggeration to make his victory seem greater. The only written records of these events come from the Romans, so they are probably biased. Most modern historians believe the actual number of soldiers involved was between 50,000 and 100,000.