The Fight At Alesia and For All of Gaul
The conflict between the armies of Caesar (Romans) and Vercingetorix (the Gauls) was hard fought and can be divided into five actions.

First: was Vercingetorix's occupation of the oppidum (hill fort) of the Mandubii (a Gallic tribe). Vercingetorix had to add a walled encampment on the eastern side of Alesia to house his army.

Second: was Caesar's marching on Alesia. Caesar's army traveled along the high ground north of Alesia and then constructing a ditch or trench across the western plain beneath the walls of Alesia. Vercingetorix made a demonstration outside of Alesia at Caesar's arrival but nothing came of this except that Caesar move back from the ditch. Caesar now ordered the construction of siege works which were designed to encircle the oppidum of Alesia. These fortifications included two sets of field works; one facing Alesia and another to the rear facing any relief forces. Caesar's works encompassed 11 miles of ground all round Alesia. Caesar then built outer works cover the rear of the first works. This line of works covered 14 miles of ground and were built to block an attack on the rear of the inner works from any relieving army of Gauls. In many places Caesar's works were interrupted by difficult terrain breaking his line of works in places. Caesar established his main headquarters on the high ground south of Alesia providing Caesar with a clear view of the entire area. Caesar placed some 23 redoubts or mini camps as well as infantry and cavalry camps along the works. Circuit towers and batteries of catapults studded the works in great numbers at regular intervals. Before Caesar's works were finished Vercingetorix sent out all his cavalry to ask other Gallic tribes for assistance. Vercingetorix hoped to reduce his food supplies by reducing the size of his army. Desperate, Vercingetorix ordered the Mandubii out of their own oppidum to further conserve his food supply. The Gauls considered cannibalism if food ran out. The Mandubii, men, women and children were forced into the no man's land between the Roman works and Alesia. Caesar ordered his men not to let them pass or provide them with assistance of any kind.

Third: was the arrival of a Gallic relief force assembled from most of the tribes of Gaul. Caesar having had finished his siege works just in time. This relief force was under the leadership of Commius the Atrebatian, the two Aeduans, Virodomarus and Eporedorix along with Vercingetorix's cousin the Arvenian Vercassivellaunus made camp a mile south west of Caesar's western works. The first battle began with as the Gallic relief force deploying its cavalry and light infantry on the western plain. Caesar sent out his own cavalry supported by infantry. This lengthy battle ended with Caesar's German cavalry taking some high ground on the flank of the Gauls. The charging Germans drove the Gallic cavalry back to their camps. Many of the Gallic light infantry were destroyed. The defeat of the Gallic cavalry shocked to the Gauls.

Fourth: a day passed after this first encounter. On the western plain the Gallic relief army made a mid-night march toward the Roman works. Raising a signal Vercingetorix assembled the men in Alesia and marched out to assault the interior works of the Romans. Lead by legates Marcus Antonius and Gaius Trebonius the Romans fought off both attacks. The exterior Roman works did deadly damage to the Gauls from long range. As the Gauls got to the works they lost many men crossing the obstacles in front of the works. Vercingetorix's men achieved little moving very slowly being delayed crossing the original trench Caesar had dug upon first arriving. The Gallic relief force withdrew at day light to their own camps fearing a flank attack by the Romans. Realizing there was no break-through by the relief forces Vercingetorix withdrew his men back into Alesia.

Fifth: this stage of the battle came with 60,000 Gauls under Vercassivellaunus making a night march from their camps in the south-west to an area north of the Roman works. They encamped and rested until noon the following day. In this area of the works was broken up by the nature of the terrain; a number of camps and redoubts were built to compensate for this fracture. Two legions commanded by Gaius Caninius Rebilus and Gaius Antistius Reginus were stationed here. At mid-day the Gauls attacked these camps and works. In the south, on the western plain the Gauls attacked the works from both sides. Caesar could see what was happening. First he reinforced the northern camp by dispatching the legate Labienus with six cohorts to help. Next as the battles continued Caesar sent Brutus north with more cohorts. Brutus was followed by the legate Gaius Fabius with more cohorts. Caesar rushed through the western Roman lines giving encouragement to the Romans there, The battle turned here to Caesar's favor. Meanwhile Labienus was able to organize 11 cohorts in addition to the cohorts Caesar had sent. Caesar next ordered his cavalry in the north-east to advance well beyond the Roman fortifications. This force was mostly Germans who were to work their way to the rear of the Gauls facing Labienus. With the battle inside and out in the west winding down Caesar himself gathered four more cohorts as he moved north to assist Labienus. Combined with the flank attack by Caesar's Germans and the Romans of Labienus broke the 60,000 Gauls in the north. The Gauls fighting in the western plain had withdrawn to camp and when they realized the battle in the north was lost and Vercingetorix had also withdrawn back to Alesia, they fled in terror.

Caesar had successfully destroyed the will of Gallic resistance. Vercingetorix surrendered himself to Caesar in the days following.

Caesar was always a risk taker. Few generals would besiege so formidable a place as Alesia with an army that was equal in number to that of the besieged. Usually a force besieging an enemy fortification requires more than twice as many men. Knowing that Vercingetorix had permitted himself to be placed in a fixed position with no escape open to him Caesar took a risk. Both had made what are normally fatal errors. Caesar however, did have a disciplined, sophisticated and well trained army of combined arms which included infantry, cavalry in addition to a tremendous engineering corps. The Gauls relied on numbers and fortifications which had previously proved superior to Caesar's operations at Gergovia earlier in that same year. Vercingetorix and his Gallic forces were not equal to Caesar in the field. Consequently, Vercingetorix permitted himself to be trapped with the hope of relief from the hosts of Gallic tribes then in rebellion. Caesar was able through the use of disciplined troops and engineering skills to blunt the effect of Vercingetorix's numerical superiority.

Caesar's forces included:
10 legions of about 3600 men each being divided into 10 battalions of 360 men each. Each legion had about 60 light ballista (artillery). The entire army had a siege train with additional ballista of larger sizes. A legion was supported with a unit of 120 to 500 auxilia (non-Romans using slings, bows and javelins). There were also 300 to 500 auxilia cavalry with each legion. This cavalry force numbered about 5000. In addition there was a force of undetermined size of German horse and foot which were vastly superior to that of the Gauls in fighting spirit and ability. We think the following legions were fielded: I (or 6th), 7th, 8th, 9th, 10th, 11th 12th, 13th, 14th and 15th.

Caesar's legions totaled about 36,000 to 40,000 men. Foot auxilia 5,000 men. Auxilia Gallic cavalry 5,000. German auxilia cavalry and foot 3,000. This brings a total of somewhere in the area of 50,000.

The Gallic army included.
Inside Alesia estimated at 40,000 or fewer almost all foot.

The Gallic Relieving Army by groups
Aedui, Segusiavi, Ambivareti, Aulerci, Brannovices and Blannovii total 35,000
Arverni,Eleuteti, Gabali and Vellavii total 35,000
Sequani, Senones, Bituriges, 12,000 each total 72,000
Bellovaci and Lemovices 10,000 each total 20,000
Pictones, Turoni, Parisii and Helvetii 8,000 each total 24,000
Suessiones, Ambiani, Medomatrices, Petrocorii, Nervii, Morini, Nitiobriges,Aulerci, Cenomani 5,000 each total 40,000
Atrebates 4000
Veliocasses, Lexovii and Aulerci Eburovices 3,000 each total 9,000
Raurici and Boii 2,000 total 4,000
Aremorican, Curiosolites, Redones, Ambibarii, Caletes, Osismi, Veneti, Lemovices and Venelli 30,000 total
Bellovaci total 2,000

Cavalry 8,000 and foot 240,000

It should be noted that many of these tribes had suffered many casualties during the previous wars and that their numbers while significantly more than those of the Romans are usually inflated. The cavalry figures above are not out of order but the figures for the foot were probably half that number.