Although the occasional uprising of previously surrendered Gallic tribes was relatively minor to Caesar’s might, there became in 54 B.C. a rising tide of rebellious, armed war parties forming along the far eastern portion of Belgae.
In 54 B.C., just prior to the second expedition to Britannia, Caesar began to hear these murmurs of rebellion. So when he returned from Britannia, he set up his legions amongst the Belgae for the winter. Rebel armies indeed rose up against Rome; the rumors were confirmed. One of the Roman legions had been destroyed. Another, amazingly defended itself so dramatically that only ten percent of its men survived until Caesar arrived from Italy and rescued them. And a third legion, led by Titus Labienus, countered the assault he faced so well that the co-conspirator of the rebellion, Indutiomarus, was killed, leaving Ambiorix, King of the Eburones, as the sole chief of the rebel Belgae coalition.
Now it was a quite a serious problem that a Roman legion had been destroyed along with its two lieutenant-commanders killed, and that another legion was decimated. So, in early 53 B.C., Julius Caesar ordered three new legions to be raised with auxiliary troops levied from the provinces of his personal friend and fellow pro-consul in Spain, Gnaeus Pompeius. This not only served practical purposes as Caesar was anticipating a large war with the Belgae, but it also showed off the power of Rome’s government system: that it can suffer a defeat and yet rebound in quick fashion to levy an army greater in size than the one lost.
Before the winter of 54 B.C. was up, Caesar took four legions and marched into Nervii territory. He moved upon them so quickly, wreaking havoc along the way, that they once again surrendered upon sight of him. Then, he called all the tribes of Gaul to convene for a peace meeting in the town of Lutetia (modern: Paris, France) belonging to the Parisii tribe. A number of tribes did not participate in this convention, so Caesar determined these absent tribes to be part of the enemy rebellion. He marched on some of them again so quickly that they sent delegates to surrender before he could initiate a battery. What remained of the rebellion was a handful of tribes situated along the River Rhine in Belgae.
So, Caesar sought to deal with this by defeating the remaining rebellion’s two chiefs: Ambiorix who was leading the rebellion in Menapii territory and Indutiomarus leading out of Treveri land.
Caesar left four legions behind with the convention of Parisii. He then sent two legions to march towards Titus Labienus, the lieutenant-general who was still holed up with one legion at the winter quarters in Treveri territory. And he took five legions under his own command to the Menapii.
Caesar divided his five legions into three divisions of separate marching columns and moved so suddenly upon the Menapii, wreaking such havoc along the way, that the Menapii were immediately induced to surrender before any direct fighting broke out.
Meanwhile, Labienus received the arrival of the two legions Caesar sent and discovered that the Treveri were advancing upon him with a large force. So, Labienus left five cohorts to trail in rearguard with the baggage of supplies and set up camp a few miles away from the winter camp on high ground above a river with 25 other cohorts plus an extra force of cavalry. It is clear by indication of these numbers that Labienus was in command of three full sized legions because he had 30 cohorts in command, each legion at its fullest containing 10 cohorts.
Labienus wanted to meet the Treveri before their alleged German auxiliary could arrive, but by no means would he dare cross that nearby river and face an outnumbering force on unestablished, unfortified, unfavorable ground. So, Labienus ingeniously employed the tactic, which seemed to be often used by the Romans in the Gallic War, of feigning intimidation by hiding in their fort for days before showing signs of a retreat.
Indutiomarus had been leading some of his men out on a daily basis to harass the Roman fort. So, they jumped at the opportunity of what they thought was a cowardly Roman force about to sneak out of camp; and they did not want to wait for their German allies as this opportunity seemed precious. So, Labienus successfully lured the Treveri to cross the river and fight on Roman ground.
With a rousing speech, Labienus then inspired his men to counter the insulting idea that the Treveri thought the Romans were vulnerable cowards. He told them that Caesar would soon learn of this battle, so they should fight as if Caesar was there himself. And he told them of the greater glory that would come from defeating such a outnumberingly large host of enemy. And what of it?
In brief, as his cleverness should be noted, Labienus took advantage of his camp’s topographically defensible location then feigned cowardice by hiding his men and pulling them off the walls so that the zealously overconfident Belgae would take the bait and launch a hasty attack on his camp. At the same time, he was secretly gathering up a large force of cavalry from throughout the loyal Gallic region behind the hills nearby. So, when Indutiomarus led his army up to harass the walls of the Roman fort as he had been doing daily, Labienus suddenly ordered his whole force of new cavalry to charge directly at Indutiomarus, telling them to focus on no man but Indutiomarus only, to not swing or aim at a single other enemy until Indutiomarus was killed. And so, following these orders, Labienus’s surprise cavalry attack swept so swiftly upon Indutiomarus that the task was completed almost instantly, the rebel beheaded, and the enemy army fled.
In light of this victory, the Germans stopped their advance, turned around, and went back home over the River Rhine. The Belgae rebels dispersed and even Ambiorix backed off the cause.
Now that the Belgae rebellion was largely squashed and all of Gaul was now essentially subject to Rome, Caesar decided to cross the River Rhine again; reasons being, he wanted to punish the Germans for offering their assistance to the rebellion and to prevent further conspiracy between the two, especially as the rebel leader, Ambiorix, was still alive and believed to be crossing into Germania.
Caesar crossed the Rhine River into Germany by building a bridge near the same spot he had priorly crossed. Upon crossing, he was met by the Ubii who wanted to make it known that they were not of the Germans who sent assistance to the rebellious Belgae. By virtue of their friendly relations with Caesar over the years, they were guaranteed peace. They then told Caesar that the Suebi were forming a war force from among the armies of all the tribes they controlled, but this war party retreated north to the borders of Cherusci territory (modern: Lower Saxony, Germany) at the edge of the Bacenis Silva (modern: Harz, Germany). This was reportedly a forest so large that one could walk for over sixty days and still not reach its end. So, with such an endeavor unprepared for and relatively unnecessary to undertake, Caesar stayed in Germany for a short time to learn more about it and contemplating its differences with Gaul. From the existence of elk, oxen, and the unicorn (likely, reindeer) to the semi-nomadic lifestyles and the migration patterns of the Germanic tribes, to the diets solely consisting of animal products, to the virtue of chastity and the purportedly greater physical strength of virgins, Caesar learned more of these hunter-gatherers; that they governed each other by the socialist principal that the all people, despite one’s own power and influence, shall not own land or riches, and that hunting and constant strife amongst each other made them fit for war. Whereby, the Gauls by contrast, because of their trade with Rome and their military defeats at the hand of Rome, became softer and less obsessed with war – though once they were more valiant than the Germans, a feature brought on by their belief in the immortality and reincarnation of the soul giving them no reason to fear death. That the Germans had no class, that the Gauls had two classes, knights and druids and the rest their informal slaves owing to them debts for subsistence or protection or residency, and that those Gallic druids were an intellectual class of religious and legal leaders who were exempt from war and often went to Britannia to learn their training in adjudicating tribal affairs as that druid was an development of the Britons.
Having seemingly enjoyed his stay in Germany this time, he left to return to his business of capturing Ambiorix. But before he left, as he wanted to capitalize on his intimidation of the Germans, he broke part of the bridge touching the shore on the Ubii’s side of the Rhine, set up a fort there and left behind two legions, twelve cohorts, to guard it stationed there.
Then, he went to the territory of the Eburones (modern: Antwerp, Belgium – Brabant, Netherlands) between the Menapii and Treveri and set up camp. Ambiorix was co-king of the Eburones and rumor had him hiding somewhereabouts.
Here, Julius Caesar divided up his army. He left one legion to guard the camp and supplies. He took charge of three legions himself, sent Titus Labienus in charge of three legions to check on the Menapii to the north, and sent Gaius Trebonius in charge of three more legions to check on the Aduatuci to the west. He himself went directly to where Ambiorix was rumored to be hidden. With the two legions back on the new Rhine River border fort, thusly he divided up his army of 12 legions.
He found Ambiorix by the hand of fortune, and by that same hand Ambiorix was able to escape. Ambiorix sent word to his people that they should all hide or give away their possesions and hide out in the forests because Caesar would be after them – essentially, every man for himself. His co-king, Catuvolcus, cursed him for starting this rebellion and hung himself. Towns emptied and Caesar invited all of Gaul to join in the plunder of Eburone land as punishment for starting this rebellion.
When it came to pass that the district of the Eburones was utterly laid to waste and that, despite the high bounty placed on his head, Ambiorix had still not been caught but was reported to be living by night with his four horsemen, Caesar called another conference of Gaul. There, punishment was doled out for two of the rebellious tribes. And one of the chief conspirators of the rebellion, Acco, was put to death.
Then, having set up his legions to winter in the region now more subjugated to his Roman presence, Caesar made way for Italy with the hopes of raising a larger army having heard that Rome just passed a law enforcing a military draft of all young men.