Agreed which is why I mentioned 'total annihilation' of the enemy. But if you want to keep infrastructure or be able to exploit their resources after the war... You can't really do that. Its a decision that has to be made.

Modern (21st century) war in a semi-modern (early 20th century or earlier) vein would be hard to predict for a great many reasons. But thinking that the equation would work out the same seems pretty dicey to me.