Yes and no. Yes, one group usually emerges victorious from a war. One group will triumph and get their way, so to speak. However, even the winning group loses in some ways. The cost of war both financially and in lives is always high. One might argue that even one death is too many. Thus, even the winner loses. In this way, I would have to say no, nobody wins at war. One group will likely get their way or accomplish the goal they went to war to press, but they will lose much in the process.
Nations enter wars with objectives, and meeting those objectives, I suppose, is victory. I do think that historically many wars have ended without what we'd recognize as winners and losers, indeed many conflicts in the early modern period ended with peace treaties that simply restored the status quo antebellum. I do think that pohnpei is basically right, however, most people who argue that there are no winners in war are those who believe the costs of war outweigh any desirable outcomes.
No, I don't think you can really win a war. Wars are won when both sides decide to stop fighting and one side declares itself the winner, or the other side gives in and surrenders. There is no way to fight a war without having casualties, and “win” is very subjective. If you are fighting for something and one side gets it, I suppose that’s a win.
Yes, if you look at the idea of "winning" a war relatively narrowly. Almost all wars end with one side winning. The Allies clearly won WWII in all relevant ways.
The only way to say there is no such thing is if you say that the costs of the war always outweigh the benefits gained. I do not believe that they do.
Destroyable; war is never the only solution!