ETHICS OF WAR :

At the Dawn of Civilisation (Preaxial & Axial), there was strict code of conduct of Waring. In Mahabharata-War, the fighters could even visit enemy camps in the evening (when fighting would stop) and could have pleasant exchanges, even play with Dice.
In the dark age of Europe and Asia (Chenghis khan to Julius caessar)would not leave behind enemies or have the ethics of keeping prisoners and feed them but would simply kill all of them so that there would be none to grow and plan against.
The Modern War-fare is now unique in the sense that there bis no agreed war front .
Enemies can take shelter in hospitals, any residential area and turn it into a hiding centre of launching missiles and opponents can also on that pretext bomb and destruct all institution of civilization.
In this 21st Century of High-tech war you need to have a few atomic bombs to frighten all humanity and may even drop it depending on your genetic/psychic disposition (edxcuse me , I shall not name Hiroshima).