How Caesar Defeated 250,000 Gaulish Warriors Coming At Them From Two Sides With Only 60,000 Legionnaires

Alesia: The Roman Army at the Height of Its Power

Julius Caesar’s Gallic Wars had been raging for over five years when his legions faced their greatest test at the double siege of Alesia, a ferocious and monumental battle that was so great in numbers, logistics, and daring that it still has few rivals in European warfare to this day.

Caesar had thought Celtic Gaul, the area approximately corresponding to modern day France, Belgium, and Rhineland Germany, conquered after his initial victories during the campaigning seasons between 58 and 54 B.C. In late 54, however, as his legions were spread around the country in winter quarters and Caesar himself cut off in Italy by Alpine snows, the tribes of Gaul united and rose against the Roman occupiers. The 14th Legion was entirely destroyed after being betrayed by tribes purporting to be allies, and it looked, momentarily, like all of Caesar’s work would be undone.

gaul and roman republic

Europe immediately before Caesar’s Gallic Wars. The areas in yellow mark the borders and provinces of the Roman Republic, while those in green mark the areas controlled by the Celtic nations. Wikimedia Commons / Cristiano64 / CC BY-SA 3.0

As it was, he managed, through a Herculean effort, to move himself and his reinforcements across the snow-covered mountains into the main area of operations, and after splitting his forces, he went on the trail of the man elected by the usually fractious Gallic tribes to be their sole leader: Vercingetorix.

A very capable political and military thinker, Vercingetorix managed to elude Caesar through canny maneuvering early in the campaign, but he understood that an open engagement against the battle-hardened legions of Caesar’s host would be tantamount to suicide. With that in mind, he moved with a force of upwards of 80,000 men to the hill fort of Alesia in central Gaul, there to await further reserves from the mustering tribes.

Pursuing him furiously, Caesar settled down to a siege and completely encircled the fort with a ring of earthworks. These were elaborate ditches and ramparts, including guard towers and heavy weaponry like catapults and ballista – effectively giant crossbows. After three weeks, the earthworks stretched for over ten miles all around the fort’s perimeter, a huge trench before the fort’s walls, then a line of other ditches four hundred yards beyond that filled with water from a nearby river, before another trench and then Roman ramparts and timber breastworks. The details and numbers involved in the campaign can be recounted in such detail because Caesar kept a diary record himself and published them in book form as “De Bello Gallica (The Gallic Wars).”

It was his strategy that such an enormous number of warriors inside the cramped town, along with the ordinary inhabitants, would be forced to capitulate in a very short time. To ensure that it was not his side that fell to hunger, he had each man under his command forage enough grain and fodder for thirty days. Vercingetorix foresaw this eventuality also, and he moved to prolong his supplies as far as possible. The non-combatants of Alesia, primarily women, children, the sick, and the old, were turned out of the town, where it was assumed the Romans would allow them to pass out of the war zone.

Against the ordinary run of warfare, Caesar ordered that they were not to be allowed through the Roman lines, so they were left outside the walls of the town to hunger and the elements. The Gauls would not allow them back inside the town and in desperation, the starving people offered themselves as slaves to the Romans, who nevertheless remained unmoved in the face of their suffering.