Before this second invasion of Britain, in an attempt to keep order in Gaul while he was away, Caesar had made a preemptive strike against the Gallic tribes, taking leading tribesmen from each as hostages. In a move sure to offend Rome’s Gallic allies, he ordered the execution of an Aeduan nobleman named Dumnorix who had attempted to escape.

But all of this trouble seemed to have been for naught, as the Gauls mounted a disorganized but deadly rebellion against the Roman occupation. It was what Caesar had feared: his hold on the vast conquered lands of Gaul was tenuous, with an army spread too thin to keep the people in check after the dust settled on his whirlwind campaigns. Now, enraged by the Romans’ harsh treatment and ravenous after the quartermasters’ plunder of their harvest, diminished already by drought, they focused their anger and discontent on their conquerors.

Food shortages had put great distance between Caesar’s winter camps, and a Belgian chieftain named Ambiorix took advantage of the scattered defense to lay a trap for the Romans. He approached a camp, feigning friendship and seeking to parley with the legates in charge, Sabinus and Cotta. Ambiorix struck fear into the camp with a report that German-backed Gallic tribes were armed and ready to attack. He suggested the Romans abandon the camp for the next closest, pledging his support and safe passage. Cotta’s suspicions were overruled by Sabinus, who believed immediate escape was their only chance. At dawn the following day, they marched out with all their supplies and equipment.

Their trek began unmolested, and Sabinus and Cotta believed they had their new ally Ambiorix to thank for that. But the Belgian’s army was lying in wait. Two miles from camp, the Romans were ambushed in a ravine. They were hemmed in by trees and enemy soldiers on both sides, and a Belgian barricade blocked the road. Missiles rained down on them, and Roman legionaries fell in great numbers. Sabinus was slain as he sought out the enemy chieftain to plead for a truce. His face disfigured, Cotta circled his troops and they continued to fight. They showed courage in certain defeat: A centurion hobbled by javelins in both legs pressed his forces onward. Cotta, too, fell in battle. A small number of survivors managed to hobble back to Rome with a report for Caesar.

The northern tribes were inspired by Ambiorix’s victory, which he trumpeted as he called up others to join the revolt. This newly motivated resistance included the Nervii, whose wounds from war with the Romans were still fresh. They tried to mimic Ambiorix’s strategy, but the commander they targeted, Quintus Cicero, the orator’s younger brother, realized it was a ploy and readied his troops for battle.

The Romans had taught the Nervii how to mount a successful siege, and they compelled Roman captives to give them more insight. They acted quickly to build up fortifications, using dirt scooped by swords and their bare hands.

Cicero dispatched men with messages for Caesar, seeking reinforcements. All but one was intercepted and publicly tortured by the Nervii. But the Romans had Gallian allies in their company, and one offered up the services of his personal slave as one of the messengers. They hid this missive by wrapping it around a spear. Thanks to this contrivance, this lone messenger slipped undetected through the enemy camp, and arrived safely at Caesar’s headquarters.

The fighting escalated. The ground was littered with the bodies of invaders who had charged the camp walls, while fires set by the Nervii raged and spread on the other side.

Correspondence from Caesar – returned the same way in which it was delivered, wrapped around a spear – went undiscovered in the camp for two days. It was finally picked up by a sentry who noticed it protruding from a tower. It was in Greek, to keep its meaning hidden from any Gaul who might intercept it. The embattled Romans, weary and wounded, were encouraged by the message: Caesar was en route, a pair of legions at his back.

Caesar’s warpath was distinguishable by the distant smoke of burning Gallic villages. Alerted to his arrival, the Nervii left the camp and set after the Roman reinforcements. Cicero sent word to Caesar to prepare for an attack. The band of roughly 6,000 Romans steeled themselves and took position behind a stream, where they were met by 60,000 Nervii. But with one swift blow, Caesar’s legions scattered the oncoming forces. The Nervii fled into the surrounding wilderness, where they were hunted and slaughtered in scores.

The rest of winter in Gaul was relatively quiet, which gave Caesar time to tend to other personal and political trials. He mourned the death of his beloved daughter Julia, but more than his solace was at stake. Her marriage to Pompey had solidified Caesar’s Triumvirate. Now that allegiance was at risk. His son-in-law’s patrician sympathies were becoming more pronounced. He had started to quarrel again with Crassus, who was plotting a conquest of the Parthians, east of Asia Minor, and thus unable to help Caesar coax Pompey back into the Triumvirate.

Still far from Rome, Caesar was helpless to stop his well-crafted partnership, and his reputation, from eroding. His failure to claim Britain for Rome was viewed as a fiasco among the ruling class.

But Caesar had more immediate threats to stave off.

Rebellion was fomenting in northern Gaul, led by a familiar foe: Ambiorix. The Belgian had slipped away unscathed from the siege of Cicero’s camp and continued to evade Caesar’s troops. The Romans quashed the revolts Ambiorix had inspired, and at Caesar’s direction, took the cattle and burned the Gaul’s settlement.

As Caesar’s legions made camp for winter, he made his way back to Cisalpine Gaul. His prospects were grim. Messengers reported that Crassus had been killed.

But Caesar’s attention was on the Gauls, newly energized by an energetic young leader named Vercingetorix. This nobleman had united the previously splintered tribes of Gaul into a single force and now aimed it at Caesar’s province of Transalpine Gaul. His rebellion could potentially threaten all of Italy.

Caesar fortified his province’s chief stronghold of Narbonne and set out for battle.

Caesar dispatched his chief of staff Labienus to quell the rebellion in the northern tribes, while the general led a force west, crushing each rebel stronghold he encountered. He drove Vercingetorix back and pursued him south to his own territory. As they retreated, the Gallic warriors set fire to their own villages and crops so the Romans couldn’t plunder them for supplies.

The Romans faced another challenge at Bourges, a well-fortified town surrounded by marshes and streams. Preparing a siege, Caesar’s engineers started construction on a massive ramp, 300 feet in length and seventy feet high. But Gallian miners attacked it from underground, and warriors poured from the gates. The structure was set aflame. Roman catapults cut the Gauls down, and the blaze was extinguished.

Caesar’s engineers completed the ramp in a downpour the next day. The Romans wasted no time: Caesar’s forces scaled the walls and stormed the town, slaughtering the remaining soldiers and townspeople, leaving only a few survivors to report back to Vercingetorix.

But the Gauls still had faith in their commander, who earned their confidence again by pushing out Roman invaders from Gergovia, Vercingetorix’s home city. Then, perhaps prematurely, he unleashed his cavalry on Caesar’s forces as they returned to their camp. The Romans easily turned back the assault and pursued the fleeing survivors to the nearby fortress of Alesia, where they made another stand.

Caesar’s men encircled the hilltop stronghold and built a wall and nine miles of fortifications. But the Romans’ efforts to cut their enemy off from outside aid failed. A few Gauls slipped into Alesia before the wall was completed.

Caesar’s siege would also have to contend with a force of more than 250,000 men which had been dispatched to rescue the rebels and their leader. Caesar established a second ring of defenses. Hungry and short on supplies, the Gauls in the town struck out desperately, but ineffectually. As their reinforcements occupied Caesar’s men in the west, Vercingetorix and his army attacked.

The legions held their ground, and as the day waned, so did the fury of the assault. This was the moment Caesar was waiting for. A breeze whipped his scarlet cloak as he rallied his troops for a counterattack. The cavalry, meanwhile, scattered the Gauls’ reinforcements across the countryside. Vercingetorix’s men retreated. Conceding defeat the next morning, he laid his weapons at Caesar’s feet.

Conflicts still erupted over the next year, but the Gallic rebellion weakened without its leader. By the end of 51 B.C., Caesar’s grip on Gaul was well-established.

A Matter of Record

Caesar wrote a memoir, The Gallic War, that was regarded at the time as both a literary and historical masterpiece. Cicero was among its many admirers. “Caesar wrote admirably,” Cicero wrote in Brutus, his history of Roman oratory. “[H]is memoirs are cleanly, directly and gracefully composed, and divested of all rhetorical trappings. And while his sole intention was to supply historians with factual material, the result has been that several fools have been pleased to primp up his narrative for their own glorification; but every writer of sense has given the subject a wide berth.”

Hirtius, another contemporary — who may well have been the “fool” who completed The Gallic War - agreed that Caesar’s account was beyond compare: “These memoirs are so highly rated by all judicious critics,” Hirtius wrote, “that the opportunity of enlarging and improving on them, which he purports to offer historians, seems in fact withheld from them. And, as his friends, we admire this feat even more than strangers can: they appreciate the faultless grace of his style, we know how rapidly and easily he wrote.”

There is reason to think that Caesar wasn’t completely accurate about events in The Gallic War, relying too much on memory and failing to verify the accuracy of reports from his field commanders. Some historians maintain that he planned to finish and revise The Gallic War. One indisputable message of the book: Caesar took a long view of his legacy. He subsequently wrote a number of books and was one of the world’s first statesmen to save his official correspondence so that it could be published.

Caesar’s war in Gaul had taken an immense toll. The historian Plutarch claimed Caesar’s army had confronted Gallic forces totaling some three million men over the course of the ten-year conflict, killing one million and enslaving another million. Those numbers are impossible to verify, and likely inflated, as it was in Caesar’s interest to exaggerate the extent of the fighting. But this long and bloody conflict made him the most famous and feared man in the world.

He looked back with pride on his years as governor, rife with hard-won battles for the glory of Rome. Ahead, more battles awaited him in the political arena - the last and most vital campaign of his career.