However morbid: for anyone (military or civilian) killed in a conflict, the ecological footprint of what would have been the rest of their lives, gets striken from the record, right? I'd expect that to work out to big numbers - people go through a lot of stuff over their lifetime.

In that sense a bloody conflict would be bad for the environment short-term (due to all the military operations etc), but beneficial long-term (due to population reduction).

Of course a lot of environmental damage also results from random destruction of vehicles, buildings, industrial sites & so on.