It's important to be clear where there is play in the theory to make it clear where there is none. The view of the second commenter is sadly common:
The whole idea of war is to impose your will on others, and the best way to do that is to destroy his ability to resist. And that means to kill as many of your enemies as possible as quickly as possible, so that they give up resistance.
A view like this takes a purported fact--that in certain wars, winning is what matters (I don't doubt this commenter has WWII in mind) and uses it to reject any jus in bello restriction whatsoever. By being clear about what can change depending on the facts of the situation, one gets a sense of theory's robustness: we can address what is reasonable within the framework of proportionality, even while disagreeing as to particular policy outcomes.