I like that you relativized your own statement with words like "should" and "theoretically". Economist would typically add to such assumptions the "ceteris paribus" phrase, i.e., "all other things being equal".
I am pleased to learn you liked something I said.
So, in your example, if there are only two countries in the world, and they are at war, the superior country would win if they use "every means at [their] disposal to do so". In game theory, that model would be described as a two-player, single-stage game.
Okay, but war is not a game. A game is based on fair play, with the idea of fun.
War is based on irreconciable differences and a desire to use lethal force to impose one's position upon the other.
In reality, however, "other things" are rarely being equal, so games are much more likely to be multiple-player, multiple-stage ones. So, while in your single stage of the game in your model you might win, the reality is that you would most likely face further resistance, maybe even years down the road, from children that grew up to hate your guts, and the game would turn into a multiple-stage one (as the history of human conflict is so readily showing us through "hundred year wars", Northern Ireland, Middle East, etc.).
Again, war is not a game. It should only be waged if one is 100% sure of the ethical and survival need of the act.
The Germans and Japanese do not hate us, precisely because we were right to wage war on them. Perhaps we are hated by others because in these other instances we were not in the right to wage war to begin with ...
Your only solution to prevent it, to bring your model to its logical conclusion, is to be 100% resolved to completely, utterly, obliterate and annihilate the entire population of the enemy... and not only its army and male population, but specifically fertile women and every and any child. Human history is littered with such attempts, known as "scorched earth", "take no prisoners", "final solution", etc.
That is your twisted misunderstanding of what I said. In truth, I never said any such thing.
And here is when the game becomes rally interesting (pardon the rhetorical coldness): it stops being a two-payer game at that point. Other players, seeing the destruction of one side, would go into alliances to protect themselves from the same fate or to further their interest. The West went into the "unholy" alliance with communists, for instance.
Again, war is not a game.
Further, you again misunderstand the gist what I said. One should only go into war if it is the BEST long-term option, not to wantonly kill people just because you can.
You are simply building a straw man to knock down.
Fortunately (for the world), most leaders are aware of the complexities of the 100% wars, and are justifiably right to avoid them (and I guess their bathrooms are kept cleaner, so they do not build their view of the world on urinal "philosophy" 
(cheap shot, I admit... just could not resist 
You really shouldn't speak of "awareness" of the complexities, since you don't even understand the point I was making. Went right over your head.
Further, the bathroom saying that I used (
"If your hose is too short, and your pump is too weak, stand a little closer dude or you'll piss on your feet.") was available for reading by me, because I have the luxury of being able to "stand back" and read it while taking care of business ... so, if you have never read this saying before yourself, it is only because you are of the unfortunate "minority" whose modest dimensions force you to stand-up close to the urinal, limiting your peripheral vision
Jack
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