If one looks back at ancient times, Roman influence due to war was as great in the culture of the conquered peoples as the conquered peoples influence to Roman culture. War brought change to all. Killing means death. Death means changes, and new beginnings. War is the mechanism for change in human culture.
Death provides a cleansing of the old.
Many adult males die in war. With their deaths, ideals and traditions die, leaving families vulnerable to change. New ideas are forced upon people through their dependency on the conquering government after the war. Once beaten, the people can be molded into citizens of the new regime. During wartime, no new ideas are initiated.