I was in the military and in my experience people that chose to go into war zones, it's optional, are fucked in the head and literally enjoy killing people, I've seen it a dozen times. They want to kill.
I chose to "go into war zones" many times and none of it was to "enjoy killing people".
True, not everyone has such a choice, but I volunteered for the organization I wanted to work for and then I volunteered for multiple deployments I didn't have to go on. Many of us have that choice and make that choice.