Uh, "it obviously doesn't come close to other powers in terms of size, military might etc."
Sparta from ~650 BC until 371 BC was the single most formidable land power in the world though.
Map is not contemporary with the time of the expedition, as by 400 BC Persia had lost Cyprus and any foothold in the Balkans. Still, 10,000 Greek mercenaries under a Spartan general travelled half way across the Persian Empire, #rekt everything in their path, and then fought their way back home through hostile territory.
Sparta also won the Peloponnesian War against Athens, which at the time commanded an Empire that destroy the entire Persian Mediterranean fleet and defeated multiple Persian forces on the Ionian Coast without consequence.
I can't fathom why anybody would ever compare the Greek states to the Persian Empire. It is like comparing a thumb tack to a balloon...