Wars are expensive, that is first thing. Second, soldiers need to eat right now and where do you think food used to come from? Army "living off the land" was a thing, because supplying them was difficult and who cares. The land armies passed through used to be pretty destroyed after.

> Russia with Crimea, whose ownership value is enormously negative?

Russia does not see expansion of own territory as negative value. Also, Russians are very much making changes in Crimea.