Day after day was passing in this manner when Caesar was informed of the arrival of C. Trebonius and his troops, which raised the number of his legions to seven. The chiefs of the Bellovaci then feared an investment like that of Alesia, and resolved to quit their position. They sent away by night the old men, the infirm, the unarmed men, and the part of the baggage which they had kept with them. Scarcely was this confused multitude in motion—embarrassed by its own mass and its numerous chariots—when daylight surprised it, and the troops had to be drawn up in line before the camp to give the column time to move away. Caesar saw no advantage either in giving battle to those who were in position, nor, on account of the steepness of the hill, in pursuing those who were making their retreat; he resolved, nevertheless, to make two legions advance in order to disturb the enemy in its retreat. Having observed that the mountain on which the Gauls were established was connected with another height (Mont Collet), from which it was only separated by a narrow valley, he ordered bridges to be thrown across the marsh. The legions crossed over them and soon attained the summit of the height, which was defended on both sides by abrupt declivities.
There he collected his troops and advanced in order of battle up to the extremity of the plateau, whence the engines placed in battery could reach the masses of the enemy with their missiles.
The barbarians, rendered confident by the advantage of their position, were ready to accept battle if the Romans dared to attack the mountain; besides, they were afraid to withdraw their troops successively, as, if divided, they might have been thrown into disorder. This attitude led Cæsar to resolve upon leaving twenty cohorts under arms, and on tracing a camp on this spot and retrenching it. When the works were completed the legions were placed before the retrenchments and the cavalry distributed with their horses bridled at the outposts. The Bellovaci had recourse to a stratagem in order to effect their retreat. They passed from hand to hand the fascines and the straw on which, according to the Gaulish custom, they were in the habit of sitting, preserving at the same time their order of battle; placed them in front of the camp, and toward the close of the day, on a preconcerted signal, set fire to them. Immediately a vast flame concealed from the Romans the Gaulish troops, who fled in haste.
Although the fire prevented Cæsar from seeing the retreat of the enemy he suspected it. He ordered his legions to advance, and sent the cavalry in pursuit, but he marched slowly in fear of some stratagem, suspecting the barbarians to have formed the design of drawing the Romans to disadvantageous ground. Besides, the cavalry did not dare to ride through the smoke and flames; and thus the Bellovaci were able to pass over a distance of ten miles and halt in a place strongly fortified by nature (Mont Ganelon), where they pitched their camp. In this position they confined themselves to placing cavalry and infantry in frequent ambuscades, thus inflicting great damage on the Romans when they went to forage. After several encounters of this kind Cæsar learned by a prisoner that Correus, chief of the Bellovaci, with six thousand picked infantry and one thousand horsemen, was preparing an ambuscade in places where the abundance of corn and forage was likely to attract the Romans. In consequence of this information he sent forward the cavalry, which was always employed to protect the foragers, and joined with them some light-armed auxiliaries, while he himself, with a greater number of legions, followed them as closely as possible.
The enemy had posted themselves in a plain—that of Choisy-au-Bac—of about one thousand paces in length and the same in breadth, surrounded on one side by forests, on the other by a river which was difficult to pass (the Aisne). The cavalry becoming acquainted with the designs of the Gauls and feeling themselves supported, advanced resolutely in squadrons toward this plain, which was surrounded with ambushes on all sides.
Correus, seeing them arrive in this manner, believed the opportunity favorable for the execution of his plan and began by attacking the first squadrons with a few men. The Romans sustained the shock without concentrating themselves in a mass on the same point, "which," says Hirtius, "usually happens in cavalry engagements, and leads always to a dangerous confusion." There, on the contrary, the squadrons, remaining separated, fought in detached bodies, and when one of them advanced, its flanks were protected by the others. Correus then ordered the rest of his cavalry to issue from the woods. An obstinate combat began on all sides without any decisive result until the enemy's infantry, debouching from the forest in close ranks, forced the Roman cavalry to fall back. The lightly armed soldiers who preceded the legions placed themselves between the squadrons and restored the fortune of the combat. After a certain time the troops, animated by the approach of the legions and the arrival of Caesar, and ambitious of obtaining alone the honor of the victory, redoubled their efforts and gained the advantage. The enemy, on the other hand, were discouraged and took to flight, but were stopped by the very obstacles which they intended to throw in the way of the Romans. A small number, nevertheless, escaped through the forest and crossed the river. Correus, who remained unshaken under this catastrophe, obstinately refused to surrender, and fell pierced with wounds. After this success Caesar hoped that if he continued his march the enemy in dismay would abandon his camp, which was only eight miles from the field of battle. He therefore crossed the Aisne, though not without great difficulties.
The Bellovaci and their allies, informed by the fugitives of the death of Correus, of the loss of their cavalry and the flower of their infantry, and fearing every moment to see the Romans appear, convoked by sound of trumpet a general assembly and decided by acclamation to send deputies and hostages to the proconsul. The barbarians implored forgiveness, alleging that this last defeat had ruined their power, and that the death of Correus, the instigator of the war, delivered them from oppression, for, during his life, it was not the senate which governed, but an ignorant multitude. To their prayers Caesar replied that last year the Bellovaci had revolted in concert with the other Gaulish peoples, but that they alone had persisted in the revolt. It was very convenient to throw their faults upon those who were dead, but how could it be believed that with nothing but the help of a weak populace a man should have had sufficient influence to raise and sustain a war contrary to the will of the chiefs, the decision of the senate, and the desire of honest people? However, the evil which they had drawn upon themselves was for him a sufficient reparation.
The following night the Bellovaci and their allies submitted, with the exception of Commius, who fled to the country from which he had but recently drawn support. He had not dared to trust the Romans for the following reason: "The year before, in the absence of Caesar, T. Labienus, informed that Commius was conspiring and preparing an insurrection, thought that without accusing him of bad faith," says Hirtius, "he could repress his treason." ("Under pretext of an interview he sent C. Volusenus Quadratus, with some centurions, to kill him; but when they were in the presence of the Gaulish chief the centurion who was to strike him missed his blow and only wounded him; swords were drawn on both sides and Commius had time to escape.")
The most warlike tribes had been vanquished and none of them dreamed of further revolt. Nevertheless, many inhabitants of the newly conquered countries abandoned the towns and the fields in order to withdraw themselves from the Roman dominion. Caesar, in order to put a stop to this emigration, distributed his army in different countries. He ordered the quaestor, Mark Antony, to come to him with the Twelfth legion, and sent the lieutenant Fabius with twenty-five cohorts into an opposite part of Gaul—to the country situated between the Creuse and the Vienne—where it was said that several tribes were in arms, and where the lieutenant, Caninius Rebilus, who commanded with two legions, did not appear to be sufficiently strong. Lastly, he ordered T. Labienus to join him in person and to send the Fifteenth legion, which he had under his command, into Cisalpine Gaul to protect the colonies of Roman citizens there against the sudden inroads of the barbarians, who the summer before had attacked the Tergestini (the inhabitants of Trieste).
As for Cæsar, he proceeded with four legions to the territory of the Eburones to lay it waste. As he could not secure Ambiorix, who was still wandering at large, he thought it advisable to destroy everything by fire and sword, persuaded that this chief would never dare to return to a country upon which he had brought such a terrible calamity. The legions and the auxiliaries were charged with the execution of this plan. Then he sent Labienus, with two legions, to the country of the Treviri, who, always at war with the Germans, were only kept in obedience by the presence of a Roman army.