As a defender one is a partaker in a war. As partaker in a war one can choose to either take or not take prisoners and one can choose to torture said prisoners or not. These choices represent different levels of ethicality.
It's also not always necessarily attacker vs defender. You can have wars between two sides that both want to go to war.
Also, there was a whole period of war (the so-called Cabinet Wars, https://en.wikipedia.org/wiki/Kabinettskriege) which was for the most part just princes with smaller armies in a very constrained manner fighting each other. So it's not always the same there.
Also, there was a whole period of war (the so-called Cabinet Wars, https://en.wikipedia.org/wiki/Kabinettskriege) which was for the most part just princes with smaller armies in a very constrained manner fighting each other. So it's not always the same there.