The war or, in other words, the experience of bringing others to death and to endanger your own life cannot be understood by yourself more than the experience of your own death. And this personal experience of death never can be really understood, but only felt as a fear or a release.
On the contrary, if you are afraid of death, the death becomes even more difficult for being understood in its characteristic of being unavoidable.
For this reason, we fail to explain death by ourselves and leave it to be a subject matter of the science of biology.
The war as an experience akin to personal death follows the same pattern. It cannot be understood by those who wage it or suffer because of its cruel effects. All of them can only feel it and should leave its reasons to be understood in the frame of the science of political conditions of a nation.
Nonetheless, all of them can feel the war. And all are wrong when they take their feelings of sufferance or power as reasons for establishing the reasons of condemning or accepting the war.
A war is just or unjust only in respect of the interpretation of political conditions. It is just when the political order is endangered by enemies and their annihilation is the best solution. It is unjust when its fundamental purpose is the intention to affect the feelings of their enemies by making them to suffer (and this is the case of wars carried on against the civilians). And also, the war is unjust when it is a form of revenging feelings of sufferance by disregarding the political conditions.