

Let us observe first that there are no god given rules of war. As far as I know, Christ or Buddhas were not interested in the military aspect of humanity. As a result, the bible or Buddhist suttras dont contain any relevant information. The prophet was much more into it, hence, the qur'an is more useful but still the scholars cannot completely on what the interpretation of relevant verses should be. I dont know much about induism and sikhsim but I imagine they would not be very useful either.
With the absence of divine revelation, the rules of war are essentially a social contract. The rules of modern war such as Geneva convention, etc. have roots from the 18-th century Europe. Artillery made cities vulnerable and castles obsolete, and small armies could not protect them. The resulting rules of war were completely rational, protecting cities and infrastructure. They were more or less followed by European powers, with an exception of air raids in WW-2 and a few rogue states throughout the history.
However, are these rules applicable in the modern war, in particular, the war of terror


