Undeniably, wars involve armed conflict of some sort, inevitably leading to death and destruction. On the negative side, hundeds of millions of lives have been lost as both direct and indirect results of wars, yet on the positive side, it has at times paved the way for much brighter futures than otherwise would've been possible. Not in all cases, but many.
World War I and II were disastrous and as far as I'm concerned started for no respectable reason and ended with no respectable result. I have nothing against the Germans, but it's a fact that they basically started both world wars, and for what? To prove their might? For revenge after the humiliation of their first failure at world domination? In no way did it benefit them, but left Europe and it's millions of occupants so very devastated and wartorn. These wars were not justified.
Yet there are many civil wars which I'm sure no one can argue were worthless. The Chinese civil war up to 1949 was worth every moment, and while it may not seem like the nation's come a long way, it has, and they will continue to strive forward and seek a better future. If war can bring hope to a nation that would otherwise have been struggling to get by the day, then I believe it is justified.