What was the largest battle, by number of participants, in which ancient Rome took part? Not counting sieges.

A quick Google search reveals nothing authoritative, but some discussion threads mention the battles of Adrianople (295K), Arausio (280K), Vercellae (260K), and -although a bit of a siege- Alesia (260K) - suggested by @ed.hank.

All these numbers come from Wikipedia, and can vary a lot, so I'm looking for something more reliable. My hope is some historian has addressed this, being the question so basic (and quite infantile).

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    This question might be answerable if you could provide a time frame that you are specifically looking at, or even era (i.e. Republic, Empire etc).
    – user17382
    Feb 16, 2017 at 22:29
  • @Thomo Republic or Empire, that depends. Which one got the largest battle? ;) I could provide a time frame I guess, but If it's answerable for the Republic and for the Empire, then it should be answerable for both.
    – Brasidas
    Feb 16, 2017 at 23:20
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    I tried researching this, but there are rather a lot of badly-documented battles with the Persians that have no estimates for one or both sides' force strengths. However, that's where Rome's largest and toughest legions tended to be, and Persia was a major empire as well, so they were likely quite large. For example, for the Battle of Edessa we don't know how large the Sassanid army was, but we do know it laid siege to a Roman army of 70,000.
    – T.E.D.
    Feb 17, 2017 at 2:56
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    @KorvinStarmast - i will make it an answer if no one else has a better one, and I can find some appropriate sources on the numbers. counts in ancient battles are notoriously off.
    – ed.hank
    Feb 17, 2017 at 13:15
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    I would discard battles of Arausio, Vercellae and Alesia. Basically because: 1. Those battles included a lot of civilian population on the barbarian side and 2. The regions which can support large amounts of soldiers living of the local food where mostly central Italy and the east side of the Empire.
    – Santiago
    Feb 17, 2017 at 19:05

1 Answer 1


According to wikipedia I would say that Adrianople is the biggest battle, not only because it was a battle between Romans (so it has sources from both sides), but also because only eastern parts of the Empire and Italy were able to support such huge numbers in an army. While other battles might look great as well, all of them were against barbarians, whose numbers can't be that big counting only warriors.

But I'll also put another battle that might potentially be bigger, battle of Phillipi, during the civil war after Caesar's death. Where 36 legions were in battle, and it might have numbers above 300,000 if those legions had auxiliary forces.

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