I think you're also thinking War Criminals can only exist in the modern era.
By definition, that’s true. The kind of international law and bodies needed to define and persecute war crimes did not exist in the Dark Ages, for example.
Take a look at the list of atrocities caused by the Mongols, Huns, and other extreme invading armies prior to modern warfare, and those would definitely be war crimes as well. Genghis Khan is probably the worst war criminal in history
Those are not the most straightforward examples. The Mongols and the Huns were not genocidal, for example.
But I’ll give you a couple other examples that are more straightforward in supporting your case.
Julius Caesar sought the extermination of the Gauls in modern-day France. He literally and proudly wrote back to Rome about how his campaign was killing “a million” Gauls.
Charlemagne sought the extermination of the Saxons in modern-day Germany. He literally ordered the execution by sword of nearly 5,000 surrendered Saxons at the Massacre of Verden.
But these are extraordinary — in both a good and bad sense — men.
Unless your character is taking on a similar place in the BT universe (Great House Lord, March Lord, etc.), he is among the rank-and-file in Caesar’s legions or Charlemagne’s host.
And those legions and that host were not composed of thousands of mass murderers and serial killers. Rather, they were composed of legionnaires, cavalry, and footmen who were doing their duty for Caesar, Emperor, payment in salt, payment in coin, feudal title/holding, or so they could just get back home.
They didn’t possess Caesar’s ridiculously outsized ambition or Charlemagne’s political and religious zeal. They were just getting the job done.
Again, if you want to portray your character as immoral and evil, go for it. It’s probably more interesting and certainly easier from a storytelling point of view.
I’m just saying that most war criminals in the kind of position your character likely occupies are amoral, not immoral, and they don’t even know it. It’s not evil geniuses, but the banality of everyday evil that makes war crimes possible.
Even in my native country, we had an air force officer of high rank, who may not have been committing war crimes, but was a serial killer and other serial thing.
This is my point.
That was a career serial killer who somehow managed to also maintain a career in the military. He would have been an immoral murderer no matter where he went or what he did.
That psychology is very different from the average war criminal. War criminals are not murderers outside the wartime environments they’re placed in and the wartime commands they’re given. It is that unique combination of extreme circumstance and unthinking conscience that turns them into amoral murderers.
Maybe what you’re looking for is not necessarily a war criminal, but rather a murderer who also happens to be a soldier.
FWIW...
