**It would require** a massively-expensive conflict that collapses the economies of those involved. But it has to go much farther. Countries have continued to fight wars with devastated economies. This war must *destroy all trade* and all firms and all capital...and all their associated structure...

**AND** destroys knowledge management (schools, libraries, etc) including professional knowledge (banking, law, medicine, science, technology) and practical survival/fieldcraft (navigation, calendar, weather, domestication, food preservation)...

**AND** utterly devastates the social fabric of both societies so deeply that parents won't pass much on what they do know to the next generation...

**AND**, of course, wipes out most infrastructure (energy, communication, food, libraries [again!]) to prevent survivors from collaborating.


Hmmm. Even Genghis Khan wasn't even close to that devastating.

Not sure how you would keep the survivors from collaborating to rebuild, say, a bit of electrical power or a water pump or a radio or using double-entry accounting or a calendar. A lot of this knowledge is just so darn *useful*.