“The apex of Egypt's Middle Kingdom had redefined the powerful hydraulic nation. The catastrophe that marked the end of this period of prosperity and regional integration appears to have been a climate-induced migration crisis. it contained a crucial insight that would go unheeded by most subsequent hydraulic hegemons: In the relationship between water and society, the resilience of the state is not just a function of its proficiency in harnessing its own resources; it is equally a function of all others in the system succeeding at doing the same.”