Rome versus Pyrrhus

[Justin of the New Yorkii]

Justin wrote:
This is a good point; I believe it was Don Rumsfeld who said "you go to war with the army you have, not the army you wish you had," so maybe there is no need to reconcile, for example, Ross Cowan's 4,800 man legion with a 5,000 man legion from some other source.

Was it really that hard for an ancient historian to write 4800 men, than it is to write 5000 men?

I'm not sure if I'm certain what you are asking, but are we trying to determine the size of a legion according to the information available to that historian, or are we trying to determine the actual number of men present on the battlefield?

If an ancient historian says that there are 5,000 men in a Roman legion, that's fine, but we can't go to him and ask "All the time? Or does that number fluctuate occasionally?"

As Paullus noted earlier, Polybius said a Roman legion would be raised of "four thousand two hundred, or in times of exceptional danger to five thousand" men. But what does "exceptional danger" mean, in Polybius' time and afterward?

It still doesn’t rule out the US army has a standardised regiment on paper. Or are you saying the US makes it up on a daily basis?

Well that's my point. Even on paper, the size of a US army regiment depends on its mission at any given time. Some only have about 2,000 men, some have over 5,000. They don't even have a standard number of battalions per regiment. It's usually three, but some regiments have four or even five battalions.