Estimates on size of armies

One thing that has always puzzled me is the vast difference in the estimation of the size of armies, done by contemporary historians and the ones done by scholars of ancient times.
For instance where ancient scholars put the numbers in hundreds of thousands, present day historians put them in thousands. I was reading about the Battle of Dorylaeum, and the difference in estimates is very large.

So my question is how exactly did they count the number of men back in those days (or in days of antiquity), and how do historians today estimate those numbers? And why do they always reach on such different figures?

I mean I understand that people back then might have exaggerated the numbers to make things seem more...impressive...but still how do the people today know?

For modern estimates, historians consider: population censi, text hindsights about attendants, if many sources are available they look for agreed numbers...
In overall they try to come up with the most reasonable and objective conclusion...

So that means modern estimates have as much chance of being erroneous as the historical ones?

In my humble opinion modern estimates can reach size ranges, which are wholly plausible...
They don't give the exact number, but the most probable figures...
Also there are historical ones which are perfectly documented, but for the "propagandistic" ones they can come up with the closest numbers...

It's not the size that matters, it's the motion of the ocean :P

I think modern scholars also look at the size of the battle field (if its location is known). If an ancient source says that 50,000 fought there but there is really only space for maybe 10,000 to deploy, then likely there was an exaggeration.

At least some modern estimates (or at least modern criticisms of contemporary estimates) is based on population of the societies or states in question. Some of the more dramatic contemporary estimates would've been impossible to mobilize given the populations and resources supporting the armies.

I believe some of the forces only hit the ten thousand mark. Typically armies were in the hundreds arriving from different area before they mobilize into a larger force.

Hannibal apparently had the biggest army of its era on a size completely unknown at the time (~40,000), but Hannibal is subject to lots of Roman propaganda. You might think "Why would Roman's lie about Hannibal, wouldn't they want him squished?", the thing is, by having this massively unbeatable army and framing Hannibal as some military genius (very debatable) the Romans and Scipio family in particular benefit hugely, with the Scipio name becoming immortalized for their glorious victory against an unstoppable foe.

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Originally Posted by Beskar

I believe some of the forces only hit the ten thousand mark. Typically armies were in the hundreds arriving from different area before they mobilize into a larger force.

Hannibal apparently had the biggest army of its era on a size completely unknown at the time (~40,000), but Hannibal is subject to lots of Roman propaganda. You might think "Why would Roman's lie about Hannibal, wouldn't they want him squished?", the thing is, by having this massively unbeatable army and framing Hannibal as some military genius (very debatable) the Romans and Scipio family in particular benefit hugely, with the Scipio name becoming immortalized for their glorious victory against an unstoppable foe.

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Not very probable! I think Scipo had enough detractors to stop his version of events from spreading, even if he was behind those figgures, (Are you saying Polybius was induced to make the figgures up? ) would they of been allowed to stand?

Also if you compare the figgures of Roman battles to battle figgures from other ancient civilizations, they do seem to be more realistic.

Not so sure about antiquity, but for many later medieval campaigns and such there are detailed economic records (numbers of horseshoes purchased, wagons, fodder, boot soles, etc.) that can be used to estimate how large an army could have been supported.

Ajax