Scale: What Pre-Modern Battles Really Looked Like

That battle scene from Gladiator?
More men, please! Where you see a line of Romans, imagine five. Ancient armies numbered in the tens of thousands.
Sure, a thousand be-weaponed extras on-screen makes your mind go “1…2…3… Lots.” But real battles were several orders of magnitude larger.

Remember the Rod Steiger Waterloo? More cavalry, please! That should be 9,000 sabres. When you measure it out, they should fill the space between the two farmsteads. The only reason the Allied Infantry didn’t turn tail and run was because Wellington had positioned them behind a ridge so that they couldn’t see the tsunami of horseflesh about to wash around their squares.
Take an earlier battle on the same scale; Chalons — Huns and “allies” versus some Romans and lots of Romanized barbarians who hated each other. Jordanes says Chalons left 150,000 men dead on the field. That has to be a wild overestimate. However, suppose he’s out by a factor of ten and the body count reflects 10% of the men fighting… that takes us back to one hundred and fifty thousand warriors jostling and yelling, say about 75,000 a side.