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I would say war is necessarily highly developing, it is mostly people who wish to defame war as much as possible that often say it is not. But war almost necessarily requires innovation to perform. Even just outthinking someone is a form of progress. But the ways you out-think someone can be extremely variable, and often have huge societal effects. It does wonders for the nutrition and musculature of your general, male populace, if you institute a rigorous, mandatory levy training. People like to think about systems as closed, specific and otherwise, but the more I learn, the less I can see where the borders lie. Fritz Haber is a fantastic example of this. A scientist, but an ardent patriot and soldier, who simultaneously is the reason ~50% of this planet's current population exist (somewhat), but is also the reason we have far more effective explosives of all kinds in the military, chemical weapons, and other such things.