So-called 'Battle of Faesulae' (406 CE).

[Steven James]

Stilicho, Radagaisus, and the so-called 'Battle of Faesulae' (406 CE). Journal of Late Antiquity 9 (1).
 
https://www.academia.edu/26695912/2016._Stilicho_Radagaisus_and_the_so-called_Battle_of_Faesulae_406_CE_._Journal_of_Late_Antiquity_9_1_

[Julian de Vries]

I do not understand why all these academics always underestimate the sizes of steppe armies. They always say: NOPE cannot happen, grossly inflated. If the ancient Chinese were attacked by steppe warriors numbering in the hundreds of thousand’s, then why not the Romans too?? There saying that not only the western sources are wrong, but also the Chinese sources too?!

How about this, lets add up all the casualties of the Peloponnesian war. If you count all the soldiers who died you easily exceed a 100.000. And that’s just for all those that died. What about all the soldiers the Greek cities could in potential supply. Now let’s suppose that a great man united all these Greek cities and you will have a magnificent army. In this way through this tribe process could the steppe peoples amass such large armies.  If a little area like ancient Greece can grow so many soldiers then what about the gigantic steppes of Eurasia, a simple lesson in geoscience.

[Nathan Ross]

I do not understand why all these academics always underestimate the sizes of steppe armies... let’s suppose that a great man united all these Greek cities and you will have a magnificent army. In this way through this tribe process could the steppe peoples amass such large armies.

It's partly a question of logistics. While it may have been possible for ancient nations to assemble hundreds of thousands of troops, keeping them supplied over the course of a campaign would have stretched the capacity of even the most organised civilisations to breaking point (this paper - Crossing the Hellespont - provides a good survey of the massive logistical requirements of the Persian invasion of Greece). For steppe armies, keeping a vast force together and in motion would have been even harder, as much of the area they had to cover was not intensively farmed and they would be constantly scattering in search of forage.

However, at Faesulae the enemy were Goths, not steppe peoples (even if there was a probable crossover between the two). As the article points out, it seems unlikely that Stilicho's army of 15-20 thousand could have defeated hundreds of thousands of warriors, who could have overwhelmed them by weight of numbers alone. So a cautious reassessment is probably wise.

Zosimus in particular often seems to exaggerate army numbers enormously, which in some cases are contradicted by more sober estimates in other sources. Unfortunately, we have no way of knowing which is correct, or, if Z is wrong, where he might be getting his higher figures from ( we must assume, I think, that Radagaisus's barbarians kept no accurate tally of numbers, something that even the King of Persia apparently found difficult!)

[Flavivs Aetivs]

As a general rule ancient authors seem to like inflating figures by a factor of 10. Knocking a zero off the end of a number will often give you a realistic estimate for the size an army. Radagasius was not above mustering 40,000 potential combatants, or more maybe.

[Julian de Vries]

Through our experiences we have come to a different conclusion on the nature of tribal warfare mechanics.

The Mongol Qidans conquered the Koreans using 400.000 horseman.

In the year 1227 the Mongol army had 135.000 warriors.


Or compare the Goths with another semi nomadic force namely the Jin, at the beginning of the 13th century the Jin had 125.000 horsemen( and 375 000 infantry).

About Logistics, who said that the nomadic tribes are not capable of making exquisite preparations to avoid disease and famine. Who decided that? Yes logistics is essential  and this is why Radagaisus  army was split in multiple parts and the Romans wanted to use the Fabian strategy.

I have not studied Zosimus’s likes and dislikes. Does he double or triple army numbers, I know not. I also do not say that the steppe warrior armies always consisted of hundreds of thousands of warriors. The sentiment I am trying to convene is that we must not easily underestimate the ancient world and fall into prejudice.

[Flavivs Aetivs]

Attila's army probably numbered around 80,000. The only surviving mention of its size (other than Jordanes who is... well... Jordanes) survives via a garbled acouunt of Priscus in the Suda which states it was in the "tens of thousands." That, along with of course Aetius' "Not unequal" force, were the two largest armies assembled in the 5th century.