By the standards of our world, Alex is a war criminal.
He ordered:
* the use of hollows point bullets
* the use of exploding small arm ammunition with less than 400g of explosive.
* the use of anti-personnel mines
* Tried to use cluster munitions
* The unnecessary destruction of civilian infrastructure and non military targets. (This is the most debatable,)
There is also the dereliction of duty by not always disciplining his troop for committing other war crimes such as harming non combatant, collective punishment, and more.
Only some of them are considered war crimes in his world, but he also managed to commit other types of war crimes unique to this world such as:
* The use of demonic constructs
* The use of snipers to target officers
* The use of machine guns against a civilised race.
* The use of shotguns against Aura Knight
* Unfair treatment of captured nobles.
* Unfair treatment of captured enemy purebreed warbeasts
* Failure to accept official challenge to a duel
* Recrutement of women as soldiers.
He also broke multiple laws of the empire he is part of, but some of these are spoilers.
Surprisingly, despite the appearance of his soldier, he is innocent of the crime of using chemical weapons.
His defence for most of these is : “yeah, I did all of that. What are you going to do about it? Arrest me?”