You weren't talking about things happening "in the heat of battle" though. Also this historically isn't actually the case, the Brits and Germans in WW2 were actually pretty honourable towards each other, generally the Allies treated POWs with respect and the Germans did the same thing. This is why Germans deliberately surrendered to American and British forces and absolutely did not want to surrender to Russian forces. We're seeing similar now with how Russia and Ukraine are treating each other, I imagine Ukraine is behaving a little better given leaks of war crimes to Western media would give them bad PR, but both sides are realistically using torture and killing POWs. This is incidentally why we should look for a peaceful outcome rather than dragging this war out for countless years, so many young men will have been killed in horrific ways that the world will never know about.