Hello; I started reading a novel by Patrick Robinson a few days ago, Intercept. This is a work of fiction and a plodding read, but the first chapter spells out fairly well the different points of view between terrorists, western politicians and the western military. For a point of reference Robinson also co wrote the non fiction story named Lone Survivor from which a movie was made.
Some enemies have little to no restrictions, moral or otherwise, about the way they wage a conflict. Using civilians as shields, using chemical or biological weapons, mistreatment of prisoners and so on.
War is not a civilized thing any more. The may have been some decent rules way back but the basis for those rules started to go away around the time of the American Civil War. That was among the first wars pretty much decided by industrial might, technology (telegraph) and powered equipment ( railroads).
By the Second World War carpet bombing of civilians was acceptable. It seems to me that the current "rules" try to keep conflicts to be fought somewhere short of all out nuclear war.
It seems pretty clear that the Syrian ruler (Assaid sp?) will use everything he has to stay in power, including gas. If he did not have the backing of a major powerful country, I think he would already be gone. The question seems to be do the major powers want to go to it over Syria?
China is pushing things in the South China Sea. Another place where major powers might escalate things to an all out war.