Warfare is not based on the biological desire to kill. Soldiers don't "get off" on it. The evidence points in this direction.

The purpose war is to get the representative of the other nation to die. His death is required because he represents an alternative sacred object. In the First World War, some men worshipped Great Britain, others France, others Germany. Western people (unlike Asians) believed that there can be only one god. Killing  the other means killing representatives of a group of people that don't believe in the one (true) god.

Warfare is the opposite of cultural relativity. There can be only ONE TRUTH; one god. If Germany is GOD, France cannot be god, nor can Great Britain.

War is undertaken to prove which entity is the one true god. It's getting the other guy to die because he doesn't believe in god. Warfare's purpose is to prove the god (the nation) that the other nation worships is a false god. 

Warfare and terrorism function according to the same dynamic: DEATH TO THE NON-BELIEVER. The other must die because he doesn't believe in your god, thus negating the meaning of existence.

Warfare is based on abstract ways of thinking; killing is spiritual: kill those whose existence negates your own sacred ideal; destroys the meaning of your existence. 

Richard Koenigsberg