[charles-salvia]

>> What concentration camps reveal is that modern people are squeamish about killing.

Well, there's a difference between exterminating a foreign and/or conquered city-state, and isolating/quarantining undesirable sub-groups from within a larger civilization (often for reasons that are more ideological than political). What the Mongols, Romans, Assyrians, etc., did was less like isolating an ethnic sub-group and more like inflicting punishment upon a city-state for not paying tribute. (Also, I think the Assyrians would also export the population of a city-state and resettle them elsewhere, to remove their national identity, just as often as they would kill and/or skin-alive everyone in a targeted city-state.)

It's probably worth noting that what happened recently to the Yazidis in North Iraq was closer to what used to happen in antiquity.