Siege of Alesia Ends: Rebellious Gauls Defeated, Julius Caesar Triumphs

"Vercingetorix Throws Down His Arms at the Feet of Julius Caesar,"
painting by Lionel-Noël Royer (1899) [all illustrations courtesy of Wikipedia]

Today in Military History: October 2, 52 BC

We return to ancient times for today's history lesson. The military career of Julius Caesar received its exclamation point with his victory against the Gauls at the siege of Alesia. His triumph shows his military skills, the dogged determination of his men, and the engineering feats that enabled Rome to finally conquer a vast, new territory.

Background

Julius Caesar (bust possibly
done during his lifetime)

Julius Caesar (100 BC-44 BC) in the year 58 was not a happy man. Despite the fact that he governed three provinces of the Roman Republic (Cisalpine Gaul, Illyricum, and Transalpine Gaul) and had four legions at his command, Caesar was deeply in debt. In an attempt to broaden his support by the people of Rome, he launched an invasion of Gaul (modern-day France) to expand land available to the poor and army veterans, as well as increase the tax base.

After about four years, he had fought the length and breadth of Gaul, subjected all the tribes to Rome – either through direct conquest or alliances. He had also launched punitive invasions against the Germans across the Rhine River and against the Britons across the English Channel. Consequently, Caesar left several legions in Gaul, and returned to Cisalpine Gaul (despite the name, this area was basically what is today northern Italy), and began recruiting more soldiers – either for the continued pacification of Gaul, or to bolster his political standing in Rome. His political alliance with Pompey the Great and Marcus Licinius Crassus – termed the First Triumvirate – had fallen apart, and Caesar realized how vulnerable he was. The Senate was considering bringing civil charges against him for his exploits.

"Gaul is divided into three parts…" from Caesar's Commentaries

A revolt in northeastern Gaul (in what is today Belgium) broke out in the winter of 54-53 BC, resulting in the slaughtering of an entire legion. Caesar responded quickly, putting down the insurrection. This action, however, only led to further unrest the next year of 52, as many Gallic leaders now realized they needed a united front to overcome the Romans once and for all. As a result, the chieftain of the Arverni tribe was proclaimed the supreme leader of the Gallic insurrection. His name was Vercingetorix.

Vercingetorix (which may not be his true name, as it translate from ancient Gallic as "king of the warriors) is estimated to have been about 30 years old at this time. There are no contemporary descriptions of him, not even from Caesar in his "Commentaries on the Gallic Wars." Nevertheless, he must have been a charismatic young man, because within a few months nearly every major tribe in Gaul had joined his revolt.

Vercingetorix memorial, Alise-Sainte-Reine, France

Prelude to Battle

Taken by surprise, Caesar marched back into Gaul in the late winter of 52, while the Alpine passes were still snow-bound. The Romans attacked the towns of Cenabum, Noviodunum Biturigum, and Vellaunodunum, each of which fell after short sieges or blockades. After these three losses, the Gauls were not willing to meet the Romans in a stand-up fight. Instead, the main army moved from place to place, obtaining supplies and burning what they could not carry, depriving the Romans of food and other necessaries.

At one point, Caesar took the city of Avaricum (modern-day Bourges) after a siege of twenty-five days. During that siege, the Romans were on short rations, and were even forced to eat meat. [The Romans still subsisted mainly on bread.] At one point, Caesar visited his various units, offering to break the siege so his men could eat properly. The men refused, not wanting such a disgrace to fall upon their leader. The city fell after a massive assault during a terrific rainstorm, and the vengeful Romans massacred nearly 40,000 Gauls.

The Gauls then fled to the town of Gergovia. Following them with four legions (about 25,000 men), Caesar attempted to besiege this fortress, but garbled orders resulted in an unplanned assault on the main Gallic fortifications. The Romans suffered around 7400 casualties, to only 3000 for the Gauls. Chastened by the loss, Caesar decided to withdraw.

Siege of Alesia

Vercingetorix decided to regroup, refit and resupply his army at the city of Alesia (probably modern-day Alise-Sainte-Reine in eastern France). After his ignominious defeat at Gergovia, Caesar was determined to take out this single largest Gallic rebel force, stated by Caesar to be in the neighborhood of 80,000 men (maybe a slight exaggeration, but modern historians basically take it as the truth). Caesar's army consisted of 12 legions – some 50,000 men – with later reinforcements making 60,000 soldiers, including cavalry and auxiliaries.

Caesar's next moves showcased the Roman military system at its finest. Rather than make a direct, suicidal assault on Alesia, he made the decision to besiege it. Consequently, his legionaries – all capable engineers in their own right – began construction of spectacular siege works. First, they constructed 11 miles (18 kilometers) of fortifications, called "circumvallation," to shut the Gallic forces inside Alesia. The following passage, taken from Caesar's "Commentaries," describes the entrenchments. [Caesar wrote his "Commentaries" in the third person, so throughout refers to himself mainly as "he" or "Caesar."]

"He dug a trench twenty feet deep, with perpendicular sides, in such a manner that the base of this trench should extend so far as the edges were apart at the top. He raised all his other works at a distance of four hundred feet from that ditch. Having left this interval, he drew two trenches fifteen feet broad, and of the same depth; the innermost of them, being in low and level ground, he filled with water conveyed from the river. Behind these he raised a rampart and wall twelve feet high; to this he added a parapet and battlements, with large stakes cut like stags' horns, projecting from the junction of the parapet and battlements, to prevent the enemy from scaling it, and surrounded the entire work with turrets, which were eighty feet distant from one another."

The turrets mentioned above contained Roman ballistae, huge bow-like siege engines that could shot large metal-tipped arrows quite far, and were very deadly anti-personnel weapons. To provide further perimeter security:

"It was necessary, at one and the same time, to procure timber. Having, therefore, cut down the trunks of trees or very thick branches, and having stripped their tops of the bark, and sharpened them into a point, he drew a continued trench every where five feet deep. These stakes being sunk into this trench, and fastened firmly at the bottom, to prevent the possibility of their being torn up, had their branches only projecting from the ground. There were five rows in connection with, and intersecting each other; and whoever entered within them were likely to impale themselves on very sharp stakes. The soldiers called these 'cippi.' Before these, which were arranged in oblique rows in the form of a quincunx, pits three feet deep were dug, which gradually diminished in depth to the bottom. In these pits tapering stakes, of the thickness of a man's thigh; sharpened at the top and hardened in the fire, were sunk in such a manner as to project from the ground not more than four inches; at the same time for the purpose of giving them strength and stability, they were each filled with trampled clay to the height of one foot from the bottom: the rest of the pit was covered over with osiers and twigs, to conceal the deceit. Eight rows of this kind were dug, and were three feet distant from each other. They called this a 'lily' from its resemblance to that flower. Stakes a foot long, with iron hooks attached to them, were entirely sunk in the ground before these, and were planted in every place at small intervals; these they called spurs"

Seeing the incredible project being directed against them, the Gauls did not sit idly by. Vercingetorix had his cavalry make raids upon the builders, but the Romans were barely bothered by these attacks. Finally, before the ring was closed, a force of Gallic cavalry managed to escape. They went all over Gaul, seeking further reinforcements to wipe out the outnumbered Romans. Realizing that more Gauls were certainly on their way to oppose him, Caesar ordered more siege works, called "contravallation," constructed facing outwards. It was a mirror image of the circumvallation, with the same traps, trenches, siege towers, etc. but to discourage a relief force. This set of siege works was 13 miles long. Also included in the outer works were four camps constructed specifically to house cavalry units. Caesar planned to use them as his mobile reserve, going anywhere the need arose.

Reconstruction of excavated Alesia siegeworks

It took the Romans (with about 60,000 strong backs at Caesar's disposal) about 3 weeks to construct both sets of earthworks. Once they were complete, the Romans now had the unique positions of being besiegers, and preparing to be besieged.

Before the arrival of the relief army, a very disturbing incident occurred. The inhabitants of the town of Alesia, perhaps a number equal to the Gallic army, were forced out of their own city by the order of Vercingetorix. There was not enough food to feed both the Alesians and the besieged Gallic army. Therefore, the people of the city were driven out towards the Roman siege lines, with the hope that the Romans would let them through, enslave them, feed them, or expose their lines to Gallic attack. Caesar ordered that none of the Gallic townspeople would be permitted through the Roman lines. Consequently, the people of Alesia – men, women, children, and old people – were condemned to slowly starve as they watched the siege proceed.

Late in September of 52, the Gallic relief force appeared, setting up camp to the southwest of the Roman siege works. Caesar states that this relief force numbered a quarter of a million men. The rescue force's commander, Commius, realized that the forces inside Alesia were likely starving and had low morale. He attempted to communicate with Vercingetorix to coordinate attacks.

[As the only source for this battle, it is tempting to take Caesar's reported numbers at face value. However, he was surely trying to bolster his own legend by defeating such a monstrously large army. Modern historians have guess-timated the relief army's size at closer to 80,000 to 100,000 men. Even if we take Caesar's figures for the force inside Alesia at face value, the Romans were opposed by between 160,000 to 180,000 Gallic warriors, compared to his own 50,000 to 60,000 soldiers. This computes to odds of between 3 to 1 and almost 4 to 1 against the Romans.]

Days #1 and 2: Probing the Roman Ring

On September 30, the relief force made its first attack on the Romans' outer siege works beginning at about noon. Upon hearing the sounds of battle, Vercingetorix ordered a simultaneous attack on the inner siege works. However, the many obstacles and the deep trenches proved too powerful, and neither attack succeeded. The Gallic forces ceased their fighting at sunset and withdrew.

Bust of Mark Antony (Vatican Museum)

The next day the major Gallic attack occurred after sunset under the cover of night. This time the relievers met greater success and Caesar was forced to abandon some sections of his outer fortification lines. Only the swift response of the cavalry commanded by Marcus Antonius (better known to history as Mark Antony) and Gaius Trebonius saved the situation. The inner wall was also attacked, but the presence of trenches, which Vercingetorix's men had to fill in before they could cross them and attack the Roman palisades, delayed them enough to prevent surprise.

By this time, the condition of the Roman army was also poor. Despite the disparity in numbers, Caesar was able to move his forces around the perimeters of the two sets of walls, placing troops where and when they were needed. However, as they were equally besieged, food had started to be rationed; the Romans were near physical exhaustion after weeks of laboring to build the fortifications, and two hard days of fighting.

Day #3: The Final Confrontation

On October 2, a picked Gallic force of 60,000 men – led by Vercassivellaunus, a cousin of Vercingetorix – launched a massive attack on a weak point in the outer siege works. In the northwestern corner of Caesar's contravallation, there was a section of the walls that were not completely enclosed, due mainly to the rough terrain and river preventing the completion of the wall. This sector was commanded by Titus Labienus, one of Caesar's most trusted lieutenants. Seeing the attack beginning, Vercingetorix ordered his besieged warriors to make a general attack along the entire inner siege works. Over the course of the entire day, the outcome of the battle swayed back and forth, with the courage and superior training of the Romans barely holding out against the larger numbers and fanatical courage of the Gauls.

Roman legionary (courtesy of www.roman-empire.net)

With a supreme effort – and the encouragement of Caesar personally visiting every sector of the inner defenses – the Romans managed to repel all of the attacks of the inner Gallic force. By this time (it was now late in the afternoon), Labienus' sector was on the verge of collapse. Caesar then took a desperate gamble. Gathering nearly all of his reserve cavalry forces – 13 cohorts totaling about 6000 soldiers – Caesar left the safety of his siege works and launched a surprise attack on the rear of Vercassivellaunus' force.

Now realizing they were being attacked from front and rear, the Gallic relievers panicked. By contrast, seeing their commander "leading from the front," putting himself in danger (Caesar was easily seen because he was wearing a red cloak), the Roman defenders redoubled their efforts. By sunset, the Gallic warriors were demoralized and retreating back to their camp. The Roman cavalry – probably German allied cavalry, who were traditional enemies of the Gauls – rode down the retreating Gauls, slaughtering most of them.

Aftermath

As with most ancient battles, casualty figures are debatable. Modern historians estimate the Roman casualties at between 12,000 and 13,000 men. The Gallic fatalities are even more unreliable, considering the modern doubts of the size of the rebellious armies. One good death total is between 56,000 and 90,000 men. Also, besides the large amounts of booty each Roman soldier acquired, Caesar also gave every man in his army a Gallic prisoner as a personal slave. That number is set at 40,000.

Footnote #1: This battle ended the organized resistance to Roman rule. It took about another year to secure final victory in the Gallic revolt.

Footnote #2: Three years later, Julius Caesar would cross the Rubicon River in northern Italy, beginning a civil war for control of the Roman Republic. After emerging triumphant from that conflict, Caesar would be declared dictator for life by the Senate. In 44 BC, he would be assassinated for fear that he would become a king.

Footnote #3: Vercingetorix surrendered to Caesar the day after the climactic battle. He would be taken back to Rome, and languish in prison for five years until he was executed – probably by strangulation – in 46 BC.