Vercingetorix resolved to send away all his cavalry by night, before the Romans had completed the investment. He urges the cavalry, on their departure, to return each to his country, and recruit the men able to carry arms; he reminds them of his services, and implores them to think of his safety, and not to deliver him as a prey to the enemies, him who has done so much for the general liberty: their indifference would entail with his loss that of 80,000 picked men. On an exact calculation, he has only provisions for one month; by husbanding them carefully, he may hold out some time longer. After these recommendations, he causes his cavalry to leave in silence, at the second watch (nine o’clock). It is probable that they escaped by ascending the valleys of the Ose and the Oserain. Then he orders, on pain of death, all the corn to be brought to him. He divides among the soldiers individually the numerous cattle which had been collected by the Mandubii; but as to the grain, he reserves the power of distributing it gradually and in small quantities. All the troops encamped outside withdraw into the oppidum. By these dispositions he prepares to wait for the succour of Gaul, and to sustain the war.
As soon as Cæsar was informed of these measures by the prisoners and deserters, he resolved to form lines of countervallation and circumvallation, and adopted the following system of fortifications: he ordered first of all to be dug, in the plain of Laumes, a fosse twenty feet wide, with vertical walls, that is, as wide at the bottom as at the level of the ground (see Plates 25 and 28), so as to prevent lines so extensive, and so difficult to guard with soldiers along their whole extent, from being attacked suddenly by night, and also to protect the workmen from the darts of the enemy during the day. Four hundred feet behind this fosse, he formed the countervallation. He then made two fosses of fifteen feet wide, of equal depth,[525] and filled the interior fosse—that is, the one nearest to the town—with water derived from the river Oserain. Behind these fosses he raised a rampart and a palisade (aggerem ac vallum), having together a height of twelve feet. Against this was placed a fence of hurdles with battlements (loricam pinnasque); strong forked branches were placed horizontally at the junction of the hurdle-fence and the rampart, so as to render them more difficult to scale. (See Plate 27.) Lastly, he established towers on all this part of the countervallation, with a distance of eighty feet between them.
It was necessary at the same time to work at widely extended fortifications, and to fetch in wood and provisions, so that these distant and toilsome expeditions diminished incessantly the effective force of the combatants; and the Gauls, too, often attempted to harass the workmen, and even made vigorous sallies, through several gates at a time. Cæsar judged it necessary to increase the strength of the works, so that they might be defended with a smaller number of men. He ordered trees or large branches to be taken, the extremities of which were sharpened and cut to a point;[526] they were placed in a fosse five feet deep; and, that they might not be torn up, they were tied together at the lower part; the other part, furnished with branches, rose above ground. There were five rows of these, contiguous and interlaced; whoever ventured amongst them would be wounded by their sharp points; they were called cippi. In front of these sorts of abatis were dug wolves’ pits (scrobes), trunconic fosses, of three feet deep, disposed in the form of a quincunx. In the centre of each hole was planted a round stake, of the thickness of a man’s thigh, hardened in the fire, and pointed at the top; it only rose about four inches above ground. In order to render these stakes firmer, they were surrounded at the base with earth well stamped down; the rest of the excavation was covered with thorns and brushwood, so as to conceal the trap. There were eight rows of holes, three feet distant from each other: they were called lilies (lilia), on account of their resemblance to the flower of that name. Lastly, in front of these defences were fixed, level with the ground, stakes of a foot long, to which were fixed irons in the shape of hooks. These kind of caltrops, to which they gave the name of stimuli,[527] were placed everywhere, and very near each other.
When this work was finished, Cæsar ordered retrenchments to be dug, almost similar, but on the opposite side, in order to resist attacks from the exterior. This line of circumvallation, of fourteen miles in circuit (twenty-one kilomètres), had been formed on the most favourable ground, in conforming to the nature of the locality. If the Gaulish cavalry brought back an army of succour, he sought by these means to prevent it, however numerous it might be, from surrounding the posts established along the circumvallation. In order to avoid the danger which the soldiers would have run in quitting the camps, he ordered that every man should provide himself with provisions and forage for thirty days. Notwithstanding this precaution, the Roman army suffered from want.[528]
Whilst Cæsar adopted these measures, the Gauls, having convoked an assembly of their principal chiefs, probably at Bibracte, decided not to collect all their men able to bear arms, as Vercingetorix wished, but to demand from each people a certain contingent, for they dreaded the difficulty of providing for so large and so confused a multitude, and of maintaining order and discipline. The different states were required to send contingents, the total of which was to amount to 283,000 men; but, in reality, it did not exceed 240,000. The cavalry amounted to 8,000.[529]
The Bellovaci refused their contingent, declaring that they intended to make war on their own account, at their own will, without submitting to anybody’s orders. Nevertheless, at the instance of Commius, their host, they sent 2,000 men.
This same Commius, we have seen, had in previous years rendered signal service to Cæsar in Britain. In return for which, his land, that of the Atrebates, freed from all tribute, had recovered its privileges, and obtained the supremacy over the Morini. But such was then the eagerness of the Gauls to re-conquer their liberty and their ancient glory, that all feelings of gratitude and friendship had vanished from their memory, and all devoted themselves body and soul to the war.
The numbering and the review of the troops took place on the territory of the Ædui. The chiefs were named; the general command was given to the Atrebatan Commius; to the Æduans Viridomarus and Eporedorix, and to the Arvernan Vercasivellaunus, cousin of Vercingetorix. With them were joined delegates from each country, who formed a council of direction for the war. They began their march towards Alesia, full of ardour and confidence: each was convinced that the Romans would retreat at the mere sight of such imposing forces, especially when they found themselves threatened at the same time by the sallies of the besieged, and by an exterior army powerful in infantry and in cavalry.
Meanwhile, the day on which the besieged expected succour was past, and their provisions were exhausted; ignorant, moreover, of what was taking place among the Ædui, they assembled to deliberate on a final resolution. The opinions were divided: some proposed to surrender, others to make a sally, without waiting till their vigour would be exhausted. But Critognatus, an Arvernan distinguished by his birth and credit, in a discourse of singular and frightful atrocity, proposed to follow the example of their ancestors, who, in the time of the war of the Cimbri, being shut up in their fortresses, and a prey to want, ate the men who were unable to bear arms, rather than surrender. When the opinions were gathered, it was decided that that of Critognatus should only be adopted at the last extremity, and that for the present they would confine themselves to sending out of the place all useless mouths. The Mandubii, who had received the Gaulish army within their walls, were compelled to leave with their wives and children. They approached the Roman lines, begged to be taken for slaves and supplied with bread. Cæsar placed guards along the vallum, with orders not to admit them.
At length Commius and the other chiefs, followed by their troops, appear before Alesia; they halt upon a neighbouring hill, scarcely 1,000 paces from the circumvallation (the hill of Mussy-la-Fosse). The following day they draw their cavalry out of their camp; it covered the whole plain of Laumes. Their infantry establishes itself at a short distance on the heights. The plateau of Alesia commanded the plain. At the sight of the army of succour, the besieged meet together, congratulate each other, yield to excess of joy, and then they rush out of the town, fill the first fosse with fascines and earth, and all prepare for a general and decisive sally.