Julius Caesar and the Gallic Wars: How Rome Conquered Gaul (58-50 BCE)

From 58 to 51 BCE, Caesar led his legions in a brutal campaign against Gallic, Germanic, and Britannic tribes. Most of his battles ended in the mass slaughter or enslavement of enemy forces. However, in 54 BCE, the Romans suffered a rare defeat when an entire legion was wiped out by the Gallic chieftain Ambiorix. Over the next four years, Caesar’s forces fought relentlessly to suppress the widespread and fierce rebellions that followed.

The Fight Against the Helvetii: How Caesar Began His Conquest of Gaul

In March 58 BCE, Caesar received reports that the Helvetii, a Gallic tribe, were migrating across Gaul—an estimated 368,000 people, with a quarter of them fit for combat. Acting without official approval, Caesar raised new legions—mostly from Cisalpine Gaul—amassing six legions (each 25,000–30,000 men) and 4,000 cavalry. Another tribe, the Tigurini, accompanied the Helvetii but were ambushed and slaughtered by Caesar's forces during a difficult river crossing. In his Commentaries, Caesar justified the massacre by reminding Romans that the Tigurini had once killed his grandfather-in-law, Calpurnius Piso.

To attack the Helvetii, Caesar sent his senior legate Labienus with two legions to secure a hill near the enemy camp. The plan was for Labienus to remain hidden until Caesar arrived with the main force. However, veteran officer Publius Considius mistakenly reported that Labienus had failed to take the hill, prompting Caesar to retreat. The Helvetii, seizing the opportunity, attacked. Before the battle, Caesar and his officers dismounted to rally their men and fought alongside them. As the enemy approached, the Roman legions stood silent, then hurled their javelins and charged. The Helvetii retreated to higher ground just as their allies—the Boii and Tulingi—arrived with 15,000 reinforcements. Ultimately, Caesar’s forces defeated all three tribes, killing or enslaving tens of thousands.

Julius Caesar vs Ariovistus: Caesar’s First Germanic Battle 58 BCE

Gallic chieftains from the Sequani tribe once sought help from the Germanic king Ariovistus against their rivals, the Aedui. Ariovistus agreed but, beyond aiding them, settled 120,000 of his people on Sequani land. Concerned by this growing Germanic presence, Caesar—echoing Gallic pleas—sent envoys demanding Ariovistus return across the Rhine and release hostages. Confident after multiple victories, Ariovistus refused. Both sides raced to seize Vesontio, the Sequani stronghold with ample supplies and a defensible position. Caesar’s legions marched day and night, arriving first, but were soon gripped by fear as Gallic locals spread tales of the fearsome Germanic warriors. Facing possible desertions, Caesar delivered a rousing speech that restored morale.

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Ariovistus avoided battle until a full moon, believing it more auspicious—a superstition Caesar exploited by launching a surprise attack. To ensure bravery was witnessed, Caesar assigned each legate to command a legion. During the battle, the Roman left flank began to falter under Germanic pressure, but Publius Crassus

acted decisively, pulling cohorts from the third line of the acer triplex formation to reinforce the front. This turned the tide: the Germanic right collapsed, prompting Ariovistus’ army to flee. Though Ariovistus escaped, he was never heard from again.

The Belgae Uprising: Caesar’s Campaign in Northern Gaul 57 BCE

During the winter, Caesar reinforced his army with two additional legions, the 13th and 14th. Meanwhile, the Belgae tribes, united under Galba, king of the Suessiones, conspired against him. Upon hearing this, Caesar quickly returned from his winter quarters in Cisalpine Gaul and marched to the Remi tribe, who had stayed neutral. The Remi provided information on the rebel forces:

Atrebates: 15,000 fighters
Atuatuci: 19,000 fighters
Bellovaci: 60,000 fighters
Suessiones & Nervii: 50,000 fighters
Morini: 25,000 fighters
6 smaller tribes: 50,000 fighters

The loyal Aedui sent their leader, Diviciacus, and forces to distract the Bellovaci. Meanwhile, the Belgae laid siege to Bibrax, a town of the Remi, which was close to falling. Caesar sent his light troops—Balaeric, Cretan, and Numidian soldiers—to infiltrate the town at night, causing the Belgae to abandon their siege. Caesar then advanced closer to their position, but the Belgae, hindered by difficult terrain and dwindling supplies, began to retreat. Caesar sent three legions under Titus Sabinus, supported by cavalry under Lucius Cotta and Quintus Pedius, to pursue. The Romans inflicted heavy losses, and soon after, the Bellovaci and Suessiones surrendered.

The Battle Against the Atlantic Tribes: Decimus Brutus’s Naval Victory 56 BCE

In 56 BCE, a rebellion broke out along the Atlantic coast, where Publius Crassus and the 7th legion were wintering. The Veneti, the most powerful tribe, had their own fleet. Caesar ordered Crassus to move to the River Loire and build warships for the coming campaign. Meanwhile, several tribes—including the Ambiliati, Diablintes, Lexovii, Menapii, Morini, Namnetes, and Osismi—aligned with the Veneti, threatening to escalate the rebellion across Gaul. To counter this, Caesar spread out his legates:

Titus Labienus: to contact the Remi
Publius Crassus: to fight the tribes of Aquitania
Titurius Sabinus: to fight the Coriosolites, Lexovii, and Veneti
Decimus Brutus: to combat the Venetian fleet

Sabinus, Crassus, and Brutus all emerged victorious, with Decimus winning a crucial naval battle against the Veneti. Their leaders were executed, and the remainder of the Venetian people were sold into slavery. Meanwhile, Caesar focused on the Morini and Menapii, harassing them in their forest and marsh strongholds. As the campaigning season ended, he sent his army into winter quarters to prepare for the next season.

Caesar’s Massacre of the Germanic Tribes: The Usipetes and Tencteri 55 BCE

Caesar faced a new challenge in 55 BCE when the Germanic tribes Usipetes and Tencteri crossed into Gaul with 430,000 people, including about 100,000 warriors, fleeing attacks by the Suebi. Caesar offered to resettle them alongside the Ubii, but during negotiations, a clash occurred between the Germanic cavalry (800 men) and Caesar’s forces (5,000). The next day, Caesar launched a full-scale attack, slaughtering the Germanic tribes. Survivors were sold into slavery, and those who fled drowned in the Rhine. The news of the massacre took time to reach Rome and was met with disapproval when it did.

After the massacre of the Usipetes and Tencteri, Caesar sought to deter further threats from across the Rhine. The Romans built a bridge in just 10 days, with forts on either side, and once completed, they crossed into enemy territory. Caesar and his army spent 18 days wreaking havoc, burning farms, villages, and crops. Satisfied with their display of power, Caesar returned to Gaul, dismantling the bridge behind them.

Caesar’s Channel Crossing: The Invasions of Britannia (55 & 54 BCE)

Roman standard bearer leading Julius Caesar’s troops ashore during the first invasion of B

For his expedition to Britain, the Romans built 98 transport ships—80 for two legions and 18 for the cavalry—while the rest of the army remained in Gaul to deal with the Menapii and Morini. Caesar sent Commius, King of the Atrebates, as an envoy to the Britons, but a storm forced his cavalry to return to Gaul. Despite this setback, Caesar pressed on and, upon landing, fought off the Britons who had been harassing them from the shore. During the battle, a legionnaire gained fame for his bravery, as Caesar later recorded in his Commentaries: "The eagle-bearer of the Tenth offered up a quick prayer and then yelled, 'Jump down, soldiers, unless you want to give up your eagle to the enemy; everyone will

know that I at least did my duty to the Republic and my commander.'" After the battle, the Britons retreated, and many local tribes surrendered, while Commius was released. However, peace was short-lived, and soon the Britons launched a second attack, targeting a group of foraging legionnaires. The camp spotted the attack and sent reinforcements. Caesar described how the Britons used chariots to throw javelins before fighting on foot. Though this style of combat was unfamiliar to the Romans, they handled it well, and after further skirmishes, the Britons sued for peace again. Caesar returned to Gaul and was granted a public thanksgiving in Rome for his victory.

Over the winter, the Romans built 600 new transport ships and 28 war galleys for a second crossing to Britain. Caesar took 5 legions, leaving 3 legions and 2,000 cavalry under Titus Labienus in Gaul. This time, Caesar faced no immediate battle, but upon advancing inland, his forces stumbled upon a high-walled fort with a garrison of native warriors, who were quickly slaughtered. Meanwhile, a storm destroyed many of Caesar’s ships, and it took 10 days to rebuild them. During this time, the Britons elected a new leader, Cassivellaunus, who attacked Caesar with full force. However, Caesar's army repelled the Britons, and Cassivellaunus eventually sued for peace, which Caesar accepted. As the campaigning season neared its end, Caesar needed to return to Gaul. Due to the large number of soldiers, hostages, and slaves, the Romans crossed the English Channel in two trips.

The Slaughter of Sabinus and Cotta: Ambiorix’s Ambush (54 BCE)

Due to a poor harvest, Caesar spread his 8 legions across Gaul. The assignments were as follows:

Sabinus & Cotta to the Eburones
Labienus to the Remi
Gaius Fabius to the Morini
Quintus Cicero to the Nervii
Lucius Roscius to the Essuvii
Marcus Crassus & Gaius Trebonius to the Belgae

Aware of growing unrest among the Gallic tribes, Caesar anticipated an attack. Ambiorix, the chieftain of the Eburones, attacked Sabinus and Cotta’s camp, mainly composed of the 14th legion. The Gauls struggled to break through the Romans' defenses, but Ambiorix halted the assault, claiming he had been forced into it. He deceived the Romans by offering

Slaughter of Sabinus & Cotta: Julius Caesars lost legion

them a safe passage out of Eburone territory to join another Roman camp. Despite Cotta’s warnings, Sabinus trusted Ambiorix’s promise. Once they left their camp, the Gauls encircled and slaughtered the Romans. Some legionnaires escaped, but Sabinus and Cotta were killed.

Caesar’s Second Crossing of the Rhine (53 BCE)

Quintus Cicero, brother of the famous orator Marcus Cicero, also faced heavy attacks during the winter. Unlike Sabinus and Cotta, Cicero held his position and successfully withstood the siege until reinforcements arrived. News of both attacks sparked widespread rebellion across Gaul, prompting Caesar to raise two additional legions, increasing his army to ten. He then launched successful campaigns against the Carnutes, Menapii, Nervii, Senones, and Treveri, all of whom surrendered.

During this time, Caesar’s senior legate Labienus was attacked by the Gallic chieftain Indutiomarus, who, like Ambiorix, received limited aid from Germanic tribes. To cut off this support, Caesar crossed the Rhine a second time. The Ubii, a Germanic tribe, identified the Suebi as the true backers of the rebellion. Although the Suebi retreated into the forests, Caesar’s show of force sent the tribes fleeing. Returning to Gaul, he hunted down Ambiorix, who disappeared, and then exacted brutal revenge on the Eburones.

The Rise and Fall of Vercingetorix: From Hero to Captive of Rome

Siege of Avaricum

In 52 BCE, nearly all of the Gallic tribes rose in unified rebellion against Caesar. Many chieftains gathered to swear oaths of alliance, and the first blow was struck by the Carnutes, who attacked the town of Cenabum, killing the Roman garrison stationed there. News of this spread rapidly, inspiring a young aristocrat from the Arverni tribe, Vercingetorix, to raise an army and join the revolt. At the time, Caesar was in Cisalpine Gaul, and his legates were slow to respond. Upon hearing of the rebellion, Caesar quickly crossed the Alps, suppressing a minor uprising in Transalpine Gaul on his way. Once reunited with his army, he began his campaign by capturing the town of Vellaunodunum, held by the Senones, and then recaptured Cenabum.

His next target was Avaricum, a heavily fortified stronghold and one of the few towns spared from Vercingetorix’s scorched-earth policy, which aimed to deprive the Romans of resources. The siege of Avaricum was grueling, taking 25 days for Caesar’s legions to construct the siege towers necessary to breach its defenses. When the Romans finally entered the city, they showed no mercy—an estimated 40,000 inhabitants, including men, women, and children, were slaughtered.

Setback at Gergovia

Siege of Alesia 52 BCE

Labienus, having recently secured a victory over the Parisii, rejoined Caesar with his forces, and together they prepared for a decisive confrontation with Vercingetorix. The two armies clashed, with the Romans emerging victorious, forcing Vercingetorix to retreat to the fortified town of Alesia.

Caesar immediately ordered the construction of two fortifications: an inner wall to encircle Alesia and an outer one to defend against a potential relief force. The legions dug ditches and set traps between the two lines to slow any breach. Before the inner wall was finished, a Gallic cavalry detachment escaped Alesia to summon reinforcements. A large relief force, led by Commius, king of the Atrebates, arrived but failed to break the Roman defenses after two major assaults and a third attack on a hilltop camp was repelled.

With no hope of relief, Vercingetorix surrendered the next day. He was spared execution but imprisoned in Rome, where he was paraded during Caesar's 46 BCE triumph and later strangled to death.

Defeating the Bituriges, Carnutes and Bellovaci (52-51 BCE)

After Vercingetorix’s defeat, most Gallic tribes submitted to Rome, except for the Bituriges, Carnutes, and Bellovaci. Caesar led the 11th and 13th legions to quickly subdue the Bituriges with little resistance. He then took the 6th and 14th legions to deal with the Carnutes, who fled their lands to seek refuge among other tribes to escape the harsh winter.

For the Bellovaci, Caesar initially mobilized the 7th, 8th, 9th, and 11th legions, later reinforced by the 6th, 14th, and 13th. The Bellovaci regrouped under Correus, with Commius as his deputy. Both armies camped on opposite hills, unwilling to initiate combat, and the Bellovaci eventually withdrew. However, Correus stayed behind with 6,000 infantry and 1,000 cavalry to ambush a Roman foraging party. Caesar, alerted by captured scouts, countered the ambush and destroyed the attackers, killing Correus.

The Bellovaci sued for peace, which Caesar accepted. Commius escaped to Britain, where he later founded a dynasty. Caesar rewarded his troops with 200 sestertii for legionaries and 2,000 sestertii for centurions.

The Siege of Uxellodunum (51 BCE)

Uxellodunum, a hilltop town in southwestern Gaul, was the last stronghold resisting Roman rule. Led by Lucterius, who had previously raided Transalpine Gaul in 52 BCE, the tribesmen hid behind the town's defenses. When Caesar’s forces arrived, they cut off the town’s water supply, forcing the Gauls to surrender. As a final warning to other potential rebels, Caesar had the hands of each warrior cut off.

The End of the Gallic Wars: Gaul Is Conquered by Caesar

Latin became widely spoken in Gaul’s main towns, and Roman luxuries, like bathhouses with running water and central heating, were enjoyed by the wealthy. The Druidic priesthood and human sacrifice were eventually abolished. It’s estimated that one million tribesmen died in the conflict, with another million captured and sold into slavery. By this point, Caesar commanded a vast, experienced army loyal to him rather than the Roman Republic.