I've heard this claim from a few places. Sometimes they follow it up by saying maybe slavery was less common than before/after/outside Cyrus' empire. Supposedly his Zoroastrian beliefs placed value on human life such that slavery was unacceptable. Is it possible that this mighty, military expansionist empire in the 6th century BCE did not rely on slave labour? Would it not have been at a big economjc disadvantage compared to its neighbours and rivals, all of whom engaged in slavery of some kind? If this claim is false, where does it come from?

I think Cyrus is one of history's most interesting figures and I have a great interest in Persia and Zoroastrianism but I always wonder whether this claim is nonsense or not! Cheers!