The approximate evaluation of the number of Gallic troops on and outside the oppidum is:
It is generally accepted that the theoretical strength of a legion is 4000 men. At the end of the season the numbers would be therefore lower, that is, about 3000 men (56). This makes a total of approximately 21,000 men.
To these figures must be added the cavalry (VIII, 28, VIII, 36, VIII, 39), Caninius' infantry or those employed as auxiliary troops (VIII, 36), the Cretan archers, and the Balearic slingers (VIII, 40).
The total number of troops besieging Uxellodunum can be assessed at around 30,000 combatants. But, in order to evaluate the real numbers of the "expeditionary force", it is necessary to double this figure, to take account of the attendants of all kinds: slaves (57) (VII, 89), and "valets" taking care of luggage, beasts of burden carrying luggage, or pulling the war machines.
When the Roman army was on campaign, it was necessary each evening to establish and fortify a camp. At other times the legionnaire could be sent to the fields to cut wheat or to forage.
The legion was divided into ten cohorts, each comprising six centuries. At the head of each century was the "basic" non-commissioned officer: the centurion, who, broken out of line, could advance to the command of the cohort, and, for the best of them (the "Primipiles"), could attend staff meetings. Among the officers, we distinguish the tribunes, from the equestrian class, normally assigned to the supervision of the legion, the prefects exercising administrative tasks and - very exceptionally - the command of the fleet or cavalry. Finally, the legates - from the senatorial class - were direct collaborators of the proconsul who gave them any task, whether administrative (for example to maintain order in a region) or military.
Due to their different methods of recruitment and their habits, Gallic infantrymen and Romans could not attain the same speeds of displacement during a campaign, although antiquity was certainly based on a pedestrianised civilisation.
The theoretical displacement capacity of a pedestrian carrying a load of 30 to 35 kg on the back was 30 or 45 km in a day. But it is necessary to distinguish the theoretical capacity, that is, the distance that can be achieved by a pedestrian free in his movements, from that of a pedestrian slowed down by his baggage (impedimenta).
According to Goudineau (59): "In Caesar's army, in theory, movement by road was regulated: the normal daily distance should not exceed 15 km, double that in the case of an emergency and the 30 km was completed normally in five hours in good conditions, Caesar made his troops do more, and he himself often paid particular attention to his speed and that of his army, which allowed him to surprise his opponents more than once."
According to the Universal History of the Armies (60): "The Legionaries generally moved in maniples - supple infantry units organised in a column of 12 files and 10 ranks. Sometimes, if the ground permitted, they walked in parallel columns so as to be always ready for combat. A legionary army always moved with a vanguard and a rearguard of horsemen and auxiliaries. The large force consisted of the legions, with their baggage following immediately behind them. The daily leg was 24 kilometers (six leagues). In the case of an emergency the legionaries carried less weight and covered between 30 and 40 kilometers in a day. The legionary moved with all his weapons and other equipment (such as bowls and tent part) and carried up to 15 daily rations of food, 850 grams of wheat, 150 grams of bacon, 20 grams of cheese and a little vinegar. In total, each day, up to 40 kg of baggage."
Cicero (61) gives us an explicit text concerning the soldier's kit: "You see the pain, the fatigue in his movements (...) The soldier must carry food for more than fifteen days, carry all that; the helmet, the shield, the sword, our soldiers do not count them as any different from their shoulders, their arms, their hands - do not they say that their weapons are the soldier's limbs? "
Legionaries were professionals subject to strict rules. The Gauls in arms remained a motley gathering of militiamen whose indiscipline and personal quarrels obviated the effectiveness they could inherently demonstrate. Their planned displacement, without urgent circumstantial constraints such as a hasty retreat before an enemy superior in number, was therefore chaotic. Drappes project to go down to the south to ravage the province was like any long journey that required consistent organisation.
The fact that after several days of travel, the Gauls of Drappes and Lucterios considered taking refuge in an oppidum shows that Caninius' troops speed of progression was superior. Of course, the more disciplined legionaries had to walk for a significant number of hours, but the transport of baggage by pack animals rather than ox-drawn wagons represented their main advantage in speed of movement. In addition, the presence of many slaves would have relieved the burden of the Roman soldier. This explains why the Gauls, feeling closed in, had to take refuge in an oppidum.
Every day saw the distance between the two armies diminish. Thus the contingents of exploration and protection (riders, in principle) at the ends of each column could be mutually observed as soon as they entered the land of the Lemovices. The Gallic leaders had to draw the consequences.
Taking account of possible losses during the preceding campaign, the army of Caninius included around 12000 pedestrians, that is 6000 infantrymen plus the usual accompaniment of specialised workers, slaves, etc., plus 500 riders, 2000 to 2500 pack animals (mares). Carts carried dismantled artillery and various materials such as forges, tools, hand mills, etc. The whole could extend to 15 km in length.
The length of a Gallic column of 1000 pedestrians on a path allowing the passage of a wagon is calculated at 170 to 500 m based on 0.5m for the space occupied by a loaded pedestrian x500 (at two abreast) or x333 (at three abreast). The train can be provided by 30 wagons (capacity 300 kg?), that is,
30 x 10m = 300 m. By including safety intervals between the various categories, the column could occupy, provided this formation is respected, a linear space of 800 to 900 m.
The cavalry, estimated at 500 units, occupies a space of 750 to 1500 m according to the width of the path (one rank or two ranks of a troop of riders).
Thus the small army of Drappes and Lucterios could, given the estimated personnel, stretch up to 2 to 3 km for 2000 men, or 4.5 km to 6 km for 5000 fighters. The presence not mentioned in the texts, but conceivable, of women (10%) and "civilians" (20%) could have increased this length by 30%.
Armies, according to their importance and in order to avoid the dangers and inconveniences of overstretched columns, were often forced to move on a wider front. The Marshal of Puysegur (65) notes: "The great armies are obliged to march in a large number of columns, otherwise they would not advance and they hold, when marching, 4 or 5 leagues of extension".
If the oxen were forced to perform a prolonged displacement, the resulting exhaustion could be compensated for by daily replacement of animals. The most exhausted animals were destined for butchery. The cattle therefore provided energy and food. These animals were native, bought, requisitioned or supplied to the troop by their owner.
Goats and sheep moving with the columns and led by shepherds have a travelling speed such that, not counting breaks intended for grazing, these animals are capable of long journeys at a sustained rate, similar to that of a practised pedestrian.
A horse with his rider can travel 50 km per day minimum (9km/h) maximum 80 km. The evaluation of this performance applies to a rider plus his equipment of a total weight of 80 kg. This capacity can be significantly affected by the relief and the size of the load.
A cart drawn by oxen can travel daily 2.5 km per hour x 10 = 25 km. As for a horse, the capacity of oxen pulling carts depends on a number of factors. The state of the road, the relief, the size of the load and excessive fatigue can each slow progress appreciably.
At the approach of the Romans, the surrounding Cadurques had to take all their herds to safety. The perspective of the siege was to extend fear to the distant neighborhood. Everyone knew the Romans' practice of requisition, a euphemism for controlled looting, which allowed the occupying army to stock up. No text informs us whether other oppida in the region moved their animals in order to protect their property (66).
The animals accommodated on Uxellodunum must have numbered at least 500 oxen, 200 sheep brought down from higher ground, 100 goats and as many pigs, about 50 horses and some mules. To this flock would be added the animals transported by the insurgents. The total number of animals could be at least 600 oxen, 500 sheep, 100 pigs, 100 goats and 50 horses. The apparent distortion between the total number of cattle present at the time of the arrival of the Gallic army and the number retained for the siege is due to the fact that carts were used to collect wheat. Therefore oxen and other beasts of burden (horses or pack mules), were required for pulling carts or carrying loads.
Puy d'Issolud intrinsically represents a grazing capacity that, in a period of military takeover of the site, is difficult to assess. Although the oppidum was sparsely inhabited, permanent residents would have cultivated favorable areas, such as the Black Combe. Between the fortifications, houses and maintenance buildings and cultivated areas, it is estimated that the grazing areas amounted to 40% of the surface of the plateau, that is, about 30 hectares.
These rations represent a "normal" amount, an average, which would allow the animal, if not to prosper, at least to maintain the same level of weight, and the same physical state in order to provide the customary traction capacity.
The fact that animals were concentrated in enclosures can have an impact on water consumption: it is reduced if animals do not move far and are sheltered from the sun; it is increased if they are exposed to great heat.
Displacement required more copious watering, even more so during the heat of summer.
A man consumes at least 2 litres of water per day, for drinking and for cooking.
Depending on the refugee population and the garrison formed by the newcomers, human consumption (69) could be
4500 x 2 = 9000 liters of water. This ration can be reduced by half a litre, which reduces the minimum quantity of 2250 litres.
At the beginning of the siege, the animals' water consumption could amount to 10,600 litres of water. The animals could be driven to several watering places, streams and springs, since circumvallation work had only just begun.
Once the enclosure became more and more complete, access to various water supply points would have been reduced to the Loulié spring.
The water requirements at the end of the siege therefore in hteory represented 9,000 + 10,600 = 19,600 litres with a minimum of 17,350 litres.
From this quantity can be subtracted the following, as the days pass:
At the end of 48 days, all the oxen having been consumed, the water requirement would be reduced appreciably:
The reduction in water requirements is therefore calculated to be 49%, that is, a minimum daily supply requirement of
10 m3. Goatskin gourds contain about 15 litres of water. By maintaining the same consumption, this corresponds to 700 units.
The Commentaries indicate that, initially, the besieged benefitted from several water supply points. In particular, it is said that, due to the fact that the circumvallation had not been completed, it was still possible to access the river.
This crucial issue of water is therefore closely linked to the progress of the siege works. Caesar's final adventures, while representing the deus ex machina that ends the conflict, represent only a part of the military operations, concentrated into a small number of days. On the contrary, the construction of palisades and ditches to hermetically enclose the insurgents represents a long-term activity since it seems to have lasted at least thirty days.
Where does a military commander decide to start constructing a circumvallation? Where these works would be militarily the most effective while being feasible, on condition that the workers or soldiers are safe from a deadly counter-attack. The notion of efficiency applies first to the establishment of fortified camps, positions of support and observation posts.
The besieger next devotes himself to interrupting the main means of communication: roads that can take wheeled vehicles. Finally joining up, little by little, the works already realised, the project manager will ensure the definitive closure of the whole.
It is obvious that the time taken to construct a circumvallation is a function of the size of the oppidum to be enclosed, the availability of materials and the ease of moving these materials.
Whatever the source and the location of Uxellodunum, the harassment of the Romans made access to the spring perilous. Fetching water at dawn and dusk would have provided better security. The chore, which was divided into two sessions, however, represented 700 passages on the access path, a continuous file of water carriers. Arrangements to protect the files from Roman fire seem essential. These arrangements could have been walls and palisades, or sections of walls and palisades behind which the labourers could shelter, then exit unexpectedly, run to the next place of shelter, and finally accomplish their mission: fill their gourd, or hand it over to the besieged in charge of distributing the water. If such a protective constrcution had not been put in place, access to the source would have been severely disrupted by fire from the Roman assault tower. Of course, significantly reducing the water supply also reduced the length of the siege. But it was necessary to resort to capturing the water of the spring, so to a cunning plan, to prevent access to the essential liquid. This proves that the Gauls in charge of fetching water could access the spring, bearing risks of course, but minimal risks. The inverse would have quickly put an end to the siege.