There's a saying, I forget where it originates but I want to say with either Bismarck or von Schlieffen, to the effect that the closest thing to a moral philosophy of warfare is that it should be pursued as brutally and ferociously as necessary to make wars as short as they possibly can be.

Granted, it's as much of its time as were the men I named. But it nonetheless does a good job, albeit implicitly, of pointing up that the best you can do in warfare is to minimize its essential immorality.

Societies often find a moral conscious once something stops being economically (or in this case, militarily) viable.

Which strikes me as coming from the rather strange view that there must be a single reason for everything.

When in my view, it's hard for a single person to have a single reason for anything, so when many people are involved...

All's fair in love and war. There is no such thing as morality in war or nature. Just winners and losers.