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  • James Houser

52 BC - The Siege of Alesia

Updated: Jun 13, 2021

AUGUST 31 - 52 BC. Julius Caesar is in trouble. His Roman legions are stranded in hostile wilderness. He has cornered the King of the Gauls, Vercingetorix, in a hilltop fort called Alesia – but he is outnumbered by the people he has surrounded. If that wasn’t bad enough, he is himself surrounded by hundreds of thousands of angry Gauls come to rescue their king. Can the Romans emerge victorious? (Spoiler: Duh. It’s CAESAR.)


The Roman Republic was on its last legs. By 60 BC, the populist politician Gaius Julius Caesar had formed an alliance with Marcus Crassus, the richest man in Rome, and the Republic’s greatest war hero, Pompey Magnus. This alliance was called the Triumvirate, since between Caesar’s political following, Crassus’ money and Pompey’s military power, the three men could wield virtually unlimited power in the Republic. Each man also tried to maneuver himself into a dominant position in government – which in Republican Rome meant achieving military glory and gaining the support of an army.


Crassus and Pompey had already led successful campaigns, with Crassus crushing the Spartacus slave uprising and Pompey conquering most of Syria and Turkey. Crassus would try to lead another campaign in 53 BC to buttress his military reputation, but failed disastrously against the Persians. Caesar, on the other hand, turned his sights north. After his term as Consul in 60 BC, he secured the governorship of Gaul, a Roman province consisting of southern Italy and northern France. While Rome had little reason to interfere in the affairs of greater Gaul, Caesar had reasons: he needed military conquest and the financial benefits of plunder to boost his power in Rome.


Gaius Julius Caesar was not one to waste time. In his mid-50s, he was – and is – one of the towering figures of history, and a personal favorite of mine. Brilliant, energetic, ruthless and charismatic, he dominated his era. His entire essence, in fact, seemed to drive towards domination. Sexually insatiable, unfailingly ambitious, and aware of his own genius, Caesar converted his inherent energy and intelligence into an unbroken string of military victories. With those victories came a dark side – his ruthless pragmatism on campaign could and did result in massive cruelties against the civilian population. His soldiers, at first uncertain of their commander, soon saw him as something approaching a minor deity.


Caesar’s target was Gaul, a vast land that covered what we now call France, Belgium, and western Germany. This region was populated by an array of tribes the Romans called Gauls (though they called themselves Celts). From 58 to 53 BC, Caesar led multiple wars of conquest into Gaul, allying with some tribes and coercing others into submission. He led his legions – always outnumbered – into marches stretching deep into uncharted lands, laying waste to any who opposed him. The Romans were universally successful, and were fair in their own terrible way: surrender, and you would be spared. Resist, and you would be defeated but forgiven. But surrender and then attack Romans again, or make war again after you had signed a treaty of submission, and Caesar would have no mercy. Fight me, but do not betray me – even if I gain your allegiance at the point of a sword.


Caesar did not limit himself to Gaul. He was the first Roman general to cross the Rhine River – twice – leading expeditions into the dark, unmapped lands now called Germany. He launched two invasions of Britain in 55 and 54 BC, and he was the first to describe that strange and distant land full of men who painted their faces blue in battle. Oh, did I mention Caesar wrote his own campaign history? Caesar’s “De Bellum Gallico,” or “The Gaulish Wars”, is one of the most-published texts in Latin and has survived intact to our time. We don’t just know what Caesar did, the good and the bad – we have his version of events.


These accounts were undoubtedly written for public consumption in Rome to enhance Caesar’s own reputation, but they are corroborated by other sources. Caesar wasn’t just launching a campaign of near-genocidal conquest, he was bragging about it to the whole world.


It wasn’t like the Gauls took this lying down. Tribal uprisings in northern Gaul (modern Belgium) occupied Caesar for most of 54-53 BC, but he inevitably emerged victorious. At the end of 53 BC, then, Caesar was triumphant. Gaul appeared pacified. He had a veteran army scattered across the country keeping an eye on things, and had possibly added all of France, Belgium, and western Germany to the Republic’s growing territories – a truly enormous expanse of land. On top of this, he was fabulously rich and the most admired man in Rome. With all this in mind, Caesar left for northern Italy in 53 BC to take care of some bookkeeping and make some political deals back in Rome.


Caesar was wrong. Gaul was not pacified; in fact, the Celts were ready to riot. They had practiced their traditional forms of tribal – the Romans might say “barbarian” – styles of war against Caesar’s heavy infantry legions, and had been smashed every time. Alone, they would fall. Together…


One night in late 53 BC, in the dead of winter, the chiefs of dozens of Gallic tribes met at the town of Gergovia in central France. They kept their meeting secret from the Romans, for they were planning a mass uprising. The Italians had marched in, seized their food, and killed their countrymen; they laid waste to any who opposed them and had bulldozed the individual tribes. The Gauls decided to unite and with their vastly superior numbers overthrow and destroy Caesar. It was a perfect time to strike, since Caesar was out of the country. The Gauls elected the chief of the Arverni, Vercingetorix, as the King of the Gauls and their war leader.


Vercingetorix was a good choice, and is comparable to the Indian chief Tecumseh who fought the United States. Like Tecumseh, Vercingetorix faced the nearly impossible job of rallying the tribes against the superior imperialist power. Like Tecumseh, Vercingetorix persuaded the tribes to unite behind him, and even tribes that Caesar believed loyal came over to the cause of freedom. Literally hundreds of thousands of warriors were flocking to Vercingetorix, and he began to organize and train them like soldiers rather than warriors. Soon the Gauls were striking every isolated Roman outpost, starting with the town of Cenabum (modern Orleans). They captured the city, killed every Roman they found, and – critically – took the major Roman grain cache in Gaul. The scattered Roman units were in deep, deep trouble.


Caesar reacted as he always did: fast and decisively. He wore out multiple horses racing back to Gaul, brought his troops back together from their scattered, vulnerable garrisons, and marched north at top speed. One thing always strikes me about Caesar’s campaigns: the man moved *fast.* He was constantly on top of his enemies before they were ready, always striking before they believed he could, and in general just overawed his foes with his energy. Caesar retook Cenabum in January 52 BC and started fanning back out to reassume control over the province.


Vercingetorix took advantage of the harsh winter months to use scorched-earth tactics against Caesar’s isolated legions. Far from home and cut off from their supply lines, the Romans were forced to forage locally for food. Vercingetorix ordered that every bit of food or housing within Caesar’s reach be removed or burned. This caused great hardship among the Gauls, but they followed their leader. Vercingetorix’s tactics worked, forcing Caesar to storm town after town to gain local food supplies. Caesar’s army was isolated, low on food, and enormously outnumbered in hostile territory. They had their leader and their skill.


In April, Caesar went for the throat: he laid siege to Gergovia, Vercingetorix’s capital and the seat of his Arverni tribe. The Gallic King himself was there to face off against his conquering foe, and as April bled into May Caesar’s men began to flag. The Gauls had stripped the countryside of supplies and stockpiled them in the fortress. Desperate to take the town before enemy reinforcements arrived and low on food, Caesar ordered a reckless assault that failed dramatically, costing him 700 casualties. Soon Caesar was forced to withdraw, link up with his forces escaping the uprising from the north, and make his way south. He hoped to reenter Roman territory to reorganize and prepare to renew the war. Vercingetorix was determined that Caesar not escape Gaul alive.


Vercingetorix placed his army of 80,000 infantry and 15,000 cavalry in the hilltop fortress of Alesia, in the hills of eastern France, across Caesar’s line of retreat. He sent his cavalry out to delay Caesar’s army – 40,000 Roman legionaries and 5,000 cavalry. Even as Caesar pushed the Gauls’ cavalry screen back, Vercingetorix stripped the countryside of food again and pulled his army inside Alesia. The city sat atop a mesalike hill with steep sides that were virtually impossible to climb. The city walls rose as an extension of the mountainside and were flanked on both north and south by rivers. Vercingetorix also ordered a trench dug on the east and west sides of the city, making any attack horrendously perilous. Here, the King of the Gauls sat with his army, challenging Caesar to try and take Alesia – the unconquerable fortress.


Rather than assault the town, Caesar laid siege. It is generally a bad idea to surround a force that already outnumbers you, but Caesar was confident he could win. The Romans dug a trench completely around the city, 10 miles in circumference, 20 feet wide. With the excavated dirt, the Romans built a 12-foot high wall with watchtowers every 100 feet or so. Caesar had his legionaries fill the trenches with sharpened stakes, interspersed with foot-long wooden blocks and iron rods to delay and break up any assault. The Romans were proving why they were the master engineers of the ancient world, and Caesar was throwing down the gauntlet to the Gauls. You have a fortress, and you outnumber me two to one? That’s cute. I just built a fortress around your fortress.


Caesar didn’t know it yet, but he would soon dream of the days he was outnumbered only two to one. Vercingetorix had sent out messengers all over Gaul to rally men to come to his aid. As long as he held the Romans here, the Gauls could muster a huge army that would come to rescue their King in Alesia. The relief army would serve as the hammer that would smash Caesar’s army against the anvil of Alesia. Caesar had surrounded their king, now they would surround him.


Caesar learned of their approach, and ordered the construction of a SECOND wall and set of trenches, this time facing outwards. This line stretched for 14 miles again around Alesia, forming a ring of wood, mud and iron filled by the Roman forces. Caesar was here to win. He was prepared to have his army, besieging his nemesis, become besieged itself. After several months of siege, though, the city of Alesia was starting to starve. But the calculus was about to change.


The Gallic relief army arrived in October 52 BC, numbering about 240,000 infantry and 8,000 cavalry. This was a stupendously huge mass of armed men, easily the largest force a Roman army had ever fought; the armed strength of all Gaul had turned up to save their king and destroy their hated conqueror. Caesar had already gathered up any food for dozens of miles, though, and gathered it within his double walls. He continued the siege as the vast Gallic host clutched their bellies outside his walls – and the King’s men in Alesia starved. Now outnumbered by almost ten to one, Caesar’s men prepared for a fight.


They got one. The relieving army attacked twice, a vast swarm of lightly armed Celtic tribesmen using sandbags and ladders to overcome the obstacles and assault the Roman walls. Caesar was everywhere, riding along the inner road on his horse in a red cape so that his troops could see him. His strike force was a band of mercenary Germanic cavalry, men who terrified the Gauls, and he was personally in combat at multiple points throughout the struggle. The Romans barely managed to repulse the tide of men each time, and even though the Gauls broke in on occasion they were always beaten back. The Celtic warriors, who went into battle in tartans, cloth padding, and sometimes shirtless, were no match hand-to-hand for the mailed legionaries and their cold iron swords.


The third attack almost succeeded. The Gauls identified what they thought to be the weakest portion of the Roman line on the northwestern corner. They approached at night, launched a diversionary raid on the other side of the Roman walls, and when the Romans were distracted came on like a human torrent. Wave after wave of Gauls climbed onto the walls, gaining ground and holding on for the next assault element. The Romans were pressed to the point of near collapse. Veterans of eight years of conquest, starvation and hardship thought the end might finally have come. At the last minute, Caesar sent the Germanic cavalry around to attack the Gallic rear, and the assault dissolved in panic. Caesar himself led his last reserve into the fight to finally turn the tide.


Inside Alesia, Vercingetorix watched the relief army crumble and knew his cause was lost. With food supplies in Alesia almost gone, he had asked Caesar to let the civilians leave, but Caesar coldly refused; more mouths to feed meant a tougher siege for the Gauls. Vercingetorix forced the noncombatants out anyway, but the Romans refused to admit them through the barricades; the Gallic civilians sat starving outside of Caesar’s fortified wall. With the failure of the final assault, Vercingetorix had no choice but to surrender. Against towering odds, Julius Caesar had won the Siege of Alesia and defeated the Gallic Revolt.


The Romans enslaved every prisoner they took, with each legionary receiving a massive bounty and a personal slave from the loot of Alesia, and Caesar had a special ceremony where Vercingetorix knelt to give his surrender. The King of the Gauls was brought back to Rome in chains, where he would languish for six years before being a centerpiece in Caesar’s final victory parade, after which he was executed. The Romans and Gauls had to agree: you could have no greater friend, and no worse enemy, than Gaius Julius Caesar.


After Alesia, the Romans never faced another serious revolt in Gaul. Caesar’s conquest had added a huge territory with five million souls to the dominion of the Roman Republic, and the future influence of Roman civilization and Latin culture is still obvious today. Rome’s frontiers now stretched to the Rhine and the English Channel, and would do so until the final collapse of the Roman Empire.


As for Caesar, he had achieved what he wanted: military glory beyond reckoning, vast financial rewards, and a loyal army of veterans that may have been, man for man, the best military force in human history. This was just in time, because Caesar had finally fallen out with his erstwhile political ally Pompey Magnus. As Pompey maneuvered to bring Caesar down, the veterans of Alesia advanced south. With Gaul conquered, Caesar was going home – this time, to conquer his own country. In 49 BC, Caesar crossed the Rubicon, and the last Civil War of the Roman Republic began. It would spell the end of the Republic and the rise of the Empire.


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