Numbers of troops in empires vs city states

[seleucid empire]

That's the correct answer.

The size of a single army (not to be confused with the overall military strength of a state) cannot exceed a certain ammount of men defined by the logistical circumstances the army is operating in.

but the persians had 600 000 in the sythcian campaign of darius and millions in the Greek campaign of Xerxes. And despite what people say about the quality of persian troops, even a levy had to eat as much as an elite soldier didnt they? also the perisnas had huge amounts of cavalry which were probs made up of noble families from asia as well as their elite heavy infantry the immortals and Greek mercenaries

And apparently the Assyrians and Median empires before the persians raised an average of 1 000 000 troops per campaign