I liked your approach. Who was waging the war. For that you need to study the history and learn who waged the war.
Islam is not only a relgion. It is a way of life which tells you how one has to conduct himself/herself in this world. The quoted verses were revealed for the conduct of war. I presume you are supposed to be a Hindu. And if you are a hindu, then I will give an example.
What did your Lord Krishna advise Arjuna when he was fightng against Karnan? Had the Pandavas not repelled the attack of Gauravas what would have been the history. Then, where is Bhagawat Gita. Which ruler in the history of mankind has advised his soldiers/followers, after securing emphatic victory on the battlefield, do not spoil green pastures, do not spoil water resouces, do not attack women, aged, children, do not cut trees et.
