War is complicated.
Depending on the philosopher or politician, soldier or commander you ask, it's purpose is fairly varied. Resource burn, attrition, making the other poor bastard die for his country... However, in general, the international community has tended to favor diplomacy favoring modalities of war. By diplomacy friendly, of course, it's still lethal, and loved ones are not at all guaranteed to come back home, but it should result in "a warrior's death". It's frankly stupid, but psychologically, to the political classes, and to the civilian classes there is just some grim acceptance of the necessity of conventional warfare and conflict. Conflicts constrained by laws of war seems to be considered somehow "cleaner", and overall more preferable to the industrial scale manufacture of blind, blistered, or diseased cripples out of the young men and women of both sides.
There are, of course, dissenters to this type of thinking, one of which was Lincoln's War Secretary Edwin Stanton if I recall, Douglas MacArthur and Sherman may also have been counted amongst the numbers of those that advocate the practice of no holds barred, total war, where anything and everything goes, since the only moral outcome of an armed conflict is to end it as quickly, brutally, and decisively as possible. To that end, any restraint in application of force is seen as a sin or needless cruelty in prolonging the conflict.
It was and remains a rather controversial view, especially given the destructive potential most first world nations are now sitting on has led to somewhat of a retirement of the philosophy; at least as long as MAD holds out.