"--- innate brutality, savagery ---". Yes, war comes with a very high cost, both material and human life.
"--- futility of war." Depends on the leadership of the combatants. Some wars have been quite decisive.
Nature provides us a binary of flee or fight. Humans have added the possibility of negotiate. When negotiations end and neither side is willing to flee, there remains only one alternative.
How does one evaluate the "cost of human life?" The trouble is that some leaders place very little value on human life. That makes negotiation very difficult.
Early in WW II there was perceived to be a very real possibility that the Axis would win. By the time the balance had shifted sufficiently to suggest negotiations, the Allies were past negotiating and had settled on total victory.
