You don't need the kind of warfare, you do however need the mentality that an entire group, including the women and children, can be exterminated and should be exterminated. That mindset did not in any great extent exist too much prior to the Industrial Revolution, however a lot of what happened in practice doesn't make that great a difference.

The really horrible bit about this is what it means about the Herero-Namaqua Genocide, done not by the Nazis but by the Kaiser.