Under certain conditions, death consecrates life and it is the sacrificial nature of war that makes it self justifying once it gets started. War is an ivestment of blood as well as money and the waste of blood in one of the worst forms of meaninglessness. The religious dimension of war is evident also in the fact that wartime is a time of intensity and risk. Certain questions arise. Still another possible justification of war involves the cultural or political benefits to be gained from a natural sense of unity and from the energy that can be mobilized from such a unity.
National unity is a morally ambiguous occurrence.
It usually depend upon on us vs them psychology and the them may not be limited to an external enemy. Nevertheless, the positive energy generated by national unity during wartime could be used positively and serves as a reminder of the differences, which usually don't seem petty, overcome in that intense feeling of consensus. Finally, there is an ethical defense of war. I refer to the theory of the just war which is based upon the idea of self-defense. The theory itself is reasonably complex and cannot be reduced to the idea of defense to maintain territorial integrity.