Siege of Alesia

Siege of Alesia

The Roman First Triumvirate (60–51 BCE) gave Julius Caesar the consulship in 59 BCE and then a military command for 5 years (later increased to 10 years) in Illyricum (area of the former Yugoslavia) and in Gaul on both sides of the Alps (France and northern Italy). During 58–57 Caesar reduced the disunited tribes of northern France and Belgium. He also undertook amphibious operations along the Atlantic seaboard in 56. In June the next year Caesar caused a great bridge to be built across the Rhine near present-day Bonn and marched his army over it into Germany. After receiving the submission of several German tribes, Caesar returned to Gaul and destroyed the bridge.

After campaigning for three months in Britain, Caesar returned to Gaul again in 55. He planned to split up his legions and station them in different parts of Gaul for the winter. Gaul was by no means subjugated, as Caesar soon discovered, for a formidable coalition of central Gallic tribes developed against Roman rule. The uprising began in the area of present-day Orléans, a particularly important area as a meeting place of the Druids who dominated affairs throughout Gaul. This was followed by outbreaks elsewhere, including the Belgae in the northern part of Gaul. Caesar faced the distinct possibility that his legions might be destroyed piecemeal; indeed, one of his garrisons (more than a legion in size) was massacred. Another legion, at Samarobriva (Amiens), was narrowly saved from destruction.

In 53 Caesar held a series of conferences with the Gallic chiefs at Samarobriva and elsewhere in an effort to end disaffection. In 52, however, the tribes of Gaul rose in general revolt. They selected as their leader the only talented military
commander produced by the Gauls in the wars against Rome, young Vercingetorix of the Arverni tribe in central Gaul. He adopted a scorched-earth strategy, destroying all Gallic settlements that might aid the Romans. A series of battles and sieges followed. Caesar proved to be a master of both siege warfare and rapid offensive movement and showed himself to be one of the greatest military commanders in history.

The culmination of the fighting in Gaul came in the great siege of Alesia in 52. Caesar concentrated his efforts against the principal Arverni stronghold of Gergovia but was obliged to break off the siege with the revolt of the Aedui, the other principal tribe of the region. Caesar therefore recalled his deputy Labienus, whom he had sent to the north, and the two of them mounted a siege of Alesia (present-day AliseSainte Reine, France), where Vercingetorix had retired following a defeat. Alesia was situated on the top of Mount Auxois near the source of the Seine.

The siege of Alesia lasted from July to October 52. Vercingetorix commanded more than 90,000 men. Caesar had only 55,000 men, and of this number some 40,000 were legionnaires, with the remainder Gallic cavalry and auxiliaries. Caesar ordered his legionnaires to construct both a wall of contravallation and one of circumvallation; each was roughly 10 miles in circumference and incorporated a ditch 20 feet wide and deep, backed by two additional trenches 15 feet wide and deep. Behind these the Romans constructed ramparts with 12-foot-high palisades and towers every 130 yards. The Romans placed sharpened stakes facing outward in front of and in the ditches.

Caesar’s foresight in having a defensive works facing outward as well as inward was soon manifest. Responding to appeals from Vercingetorix, a vast Gallic relief force numbering as many as 250,000 men and 8,000 cavalry gathered around Alesia and besieged the besiegers. Caesar had laid in considerable stocks of food and had an assured water supply, so he calmly continued his own siege operations, repulsing two relief attempts and a breakout sortie with heavy losses.

To win time Vercingetorix tried to send out the women and children from Alesia, but Caesar refused to allow them through the lines. With the situation hopeless, Vercingetorix surrendered. Taken to Rome for Caesar’s triumph, Vercingetorix was then executed.

The defeat at Alesia broke Gallic resistance to Rome. The Gauls’ failure to unite had cost them dearly. At least a third of their men of military age had been killed in the fighting, and another third were sold into slavery. The vast majority of Gauls hastened to renew their fealty to Rome. After a few mopping-up operations the next year, the Gallic Wars were over. Gaul would be an integral part of the Roman Empire for the next 500 years. The newly conquered territories, with a population of perhaps 5 million people, proved immensely important to Rome because of their vast resources of agriculture, stock breeding, mining, and metallurgy as well as the production of pottery and glass. During the conquest of Gaul, however, Caesar’s army had grown from 2 to 13 legions, making Caesar a threat to Rome itself.


Caesar, Gaius Julius. Seven Commentaries on the Gallic War. New York: Oxford University Press, 1996.

Grant, Michael. Julius Caesar. New York: M. Evans, 1992.