The goal is to end suffering as quickly as possible, while causing as little undue suffering as possible.

As a former infantryman, I was trained to "kill people and break their stuff" as the crude Army lingo put it. We were trained to do everything possible to keep civilian casualties to a minimum while inflicting maximum damage on the enemy. The hope was to end the killing through victory. Acknowleding the enemy's suffering (as opposed to the suffering of the innocent) does nothing towards ending the fighting. When war can not be avoided, it must be won as quickly as possible. Hit the enemy, hard, repeatedly, until he surrenders or dies. Anything less and you drag out the fighting only to result in more suffering on both sides. The moment an enemy soldier surrenders, he must be treated with the same care as innocent civilians. Until then, he is a combatant and a target.

So yes, that does mean that those doing the fighting have to harden their hearts to what they're doing. That's why so many of them pay such a heavy price afterwards.