Total War During World War II:
Total war was accepted as a means to an end during the Second World War, much like the fire bombings they brought high casualties to both sides. Carpet bombing as defined by Google is: "an extensive and systematic bombing intended to devastate a large target." The idea behind is drop a lot of bombs and hopefully at least one of the bombs will hit the intended target. Each bomb was a redundancy to the one previous to it. This was done primarily in cities in order to destroy the moral of enemy citizens, hoping that they would overthrow the current government and end the war.
As a society we are given the tools to create and with the tools to create we develop horrible things, things that in nature can only destroy human life. There is a difference between killing an enemy combatant, and systematically targeting citizens. While some may argue that, civilian casualty was never necessary, what does one expect when you drop over 30,000 lbs of explosive ordinance onto a city? There is going to be a great lose of civilian life.