Caesar’s Greatest Battle

The most exciting thing in Caesar’s Commentaries?

Commentarii de Bello Gallico, an account written by Julius Caesar about his nine years of war in Gaul (public domain photo)

The battle of Alesia.
What is so exciting about it?
Caesar was so daring; so much was in the balance.
What happened?

He had eighty thousand Gauls trapped inside a town with a deep river-gorge around it. Since he couldn’t storm it, he built a wall to fence the Gauls in.
He knew they had food for only about thirty days.

Yet just before he closed the ring around the town, the Gallic cavalry escaped and ran to get help.

Caesar had fifty thousand soldiers, which was strained but acceptable for this siege, but now there was a chance that a new Gallic army would come to help their trapped countrymen before he could make them surrender. What should he do? Give up the siege?
Soon spies informed him that there was indeed a huge army a-building: 200,000 or 250,000 Gauls marching to relieve Alesia. Any general but old Gaius would have abandoned his siege and gotten out while the getting was good. Imagine: eighty thousand enemies in front of you and 250,000 coming from your back.

But Caesar hated to run away. In the town with those eighty thousand Gauls was their great king Vercingetorix. This was just too good. And anyway he reasoned that, in a way, he still had an advantageous position—or he could make himself one. Of course it took a Caesar to reason like that. And a Caesar to pull off one of the most daring plans in military history. If it hadn´t worked and he had gotten away alive he would surely have been court-martialled. After all, he did have enough time to break camp and look for a less apparently compromising position.

He had been studying siege techniques and defense-works. He was satisfied that his great 18-kilometer wall around Alesia would hold in the enemy. Why shouldn’t a similar wall and ditch be able to hold off another one, however big?

He ordered his men to start building a second wall BEHIND them. And to put towers every fifty yards and to lay clever traps everywhere in front of the wall and pointed sticks and all kinds of defense works and machines a few soldiers could handle when the enemy came. The work was hard—the soldiers had just finished the first wall and were exhausted. Maybe there wouldn’t be enough time to complete the second wall before the relieving enemy army showed up. But Caesar guessed there was. He kept his men cheerful with his famous pep-talks; and they had fun making the new booby traps and giving them names.

A reconstruction of Caesar’s outer wall and trenches (Creative Commons Attribution-Share Alike 3.0 Unported license photo).

And his hunch was right. When the huge army of Gauls showed up the new wall was finished except for one small place where because of a stream there was no way to close it.

Caesar’s twin wall around Alesia, thought to be the modern Alise Sainte-Reine, France (Creative Commons Attribution-Share Alike 1.0 Generic license photo).

Read what happened when the Gauls attacked and stumbled onto those booby-traps. Caesar’s Greatest Battle (Part 2)


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11 Responses to Caesar’s Greatest Battle

  1. Yann Gleek says:

    Your are, it would be “wrong to judge them by the brooks (or ditches!) that you see there now”…unless if two studies confirmed it:
    -Sébastien Durost, Benoît Rossignol, Georges-Noël Lambert et Vincent Bernard, « Climat, Guerre des Gaules et dendrochronologie du chêne (Quercus sp.) du ier siècle av. J.-C. », ArchéoSciences [En ligne], 32 | 2008, mis en ligne le 31 décembre 2010, URL :
    -Jonhattan Vidal et Christophe Petit, « L’eau sur le site d’Alésia : la contrainte hydrogéologique lors du siège de 52 av. J.-C. », Revue archéologique de l’Est, Tome 59-1 | 2010, [En ligne], mis en ligne le 05 janvier 2012. URL :

    Oze and Ozerain were the same brooks 2060 years ago.
    Don’t know much about Numencia but I’d like to.

  2. 100swallows says:

    Yann Gleek: Those Gallic soldiers that camped on the slope were part of the huge army that came to relieve their fellows in the town, not those that Vercingetorix had posted in front of it.
    As for the “rivers” around Alise, it is wrong to judge them by the brooks (or ditches!) that you see there now. I have never been to Alise but I’d bet that the water level has gone way down in the last centuries, as it has here in Spain at several of the old sites like Numantia. I have read that not all scholars agree that Alise is Alesia. I don’t know enough to participate in that debate. Thanks for those nice photos of the two streams.

  3. Yann Gleek says:

    @100swallows, you said on June 5, 2008 that “the Gallic soldiers were too numerous to fit inside Alesia and they camped on the slope beside it.” Caesar wrote (BG VII 71): “he(Vercingetorix) receives into the town all the forces which he had posted in front of it”. Who’s wrong?
    Then you add:”That was still well protected by rivers on two side”. Have a look at the “rivers” and tell me witch sort of protection it can give to an army ?
    L’Oze :
    Alise does’nt match at all.
    And Caesar not only gave to each of his soldiers one of the vanquished Gauls as a slave, he also restored about twenty thousand captives to the Aedui and Arverni.

  4. James says:

    anyone having lapses of genius regarding what really happened has no much credibility in my opinion..

  5. Pingback: Caesar Bet Big (Part 3) « Great Names in History

  6. 100swallows says:

    That’s a good question, Danu. I don’t know. Caesar said he stocked up on food before the Gallic army came. But if he hadn’t beaten them soon they could easily have starved him out. Perhaps he believed that his soldiers could always fight their way out or escape through some unguarded place in that long wall. He certainly believed that an army of Romans would defeat Gauls in the field, especially under his leadership. But I’m sure many experienced generals would have advised him not to wall himself in like that.

    Remember that Caesar wrote his book for Romans. The figures for his own army must have been believable–it was only the enemy numbers that he exaggerated. I read somewhere the Gallic host might have been 100,000 or 150,000–still considerable.

  7. ivdanu says:

    I was also thinking the numbers aren’t right. In her book about the 14 th century Barbara Tutchman says that usualy you have to take a 0 or so from the numbers the medieval chronicles mention for batles. Could be the same for Caesar.

    One question: how did Caesar – soon to be asiege himself – going to feed his soldiers? Wasn’t it a tricky solution, to wall himself and his army?

  8. 100swallows says:

    Madame Monet: I simplified it just a bit and there will have to be even more simplifying in the next two chapters. In fact, as you saw from that map, the Gallic soldiers were too numerous to fit inside Alesia and they camped on the slope beside it. That was still well protected by rivers on two sides (and the town of Alesia above them) but they had to build their own wall and trench below them–and a gate. Caesar built his wall around the entire Alesia hill.

  9. wpm1955 says:

    Tomorrow morning I will tell this story to my class, especially to the child in my class who had the identiy of Gaius during our Roman unit!

    This was really interesting.

    Madame Monet

  10. 100swallows says:

    Erika: As far as I know, the only numbers we have for the soldiers that participated in the battle are from Caesar’s own account. I don’t know how modern historians make their estimates but they always say Caesar’s numbers are much too high, that he exaggerated. After all, his book was propaganda. Because of those high numbers some historians even think Alesia couldn’t be the modern Alice because the site is just too small. And they point to another former oppidum in the Jura. Still, the number of Caesar’s own force must be accurate, since that could be known to Romans at the time. And he says he gave to each of his soldiers one of the vanquished Gauls as a slave—does that mean fifty thousand enemy still alive after the battle?

  11. erikatakacs says:

    Brilliant strategy from Ceasar’s part indeed. The numbers seem exaggerated, especially the relief Gaul army.

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