What kind of man kills another man? Out of revenge? Out of duty? Out of rage? Out of protection?
I cannot fathom the thought. I cannot even comprehend extinguishing the life of an other.
Perhaps you can. Please explain.

I remember seeing Saving Private Ryan for the first time. The scene where the German soldier and the American soldier end up fighting hand to hand after they both run out of ammunition. They come face to face, eye to eye, with only the thought of killing. The enemy. The German soldier ends up slowly sliding a knife into the American soldiers heart. He gazes into his eyes saying, "Shhhh. Shhhh," while the American soldier screams, "No!" repeatedly. His life is gone, ended in a moment of passion and survival. Kill or be killed. As the German soldier descends the stairs, he sees Upham--the very green, scared, ammunition toting war journalist. The German soldier passes him by without a second glance. Upham does nothing. In another battle scene, this same German soldier is shooting Upham's comrades. Upham could have prevented this, if only he would have acted. He just didn't have the stomach for it.

Was it harder to kill before gun powder? From a distance, behind a gun, you don't have to watch your enemy die. You don't have to look him in the eye and decide he is not worth living. There is separation. Objectification. Like hunting a deer. Maybe it was only harder from a technical standpoint? I don't know.

In the end, Man is and has always been his own worst enemy.