War and governance have co-evolved across the last 15,000 years, but much remains unclear about the process because historical narratives have not been integrated well into social-scientific analyses. Under the conditions of circumscription/caging that emerged in a few places after the ice age, war became productive, in the sense of producing larger, safer, richer societies. However, the larger states produced by war changed the environment around them, and for more than 1,000 years war turned counterproductive in the places that it had previously been productive, breaking up large states. After about 1400 CE a new phase of productive war began. This too began turning counterproductive in the 20th century CE. The most important question for the 21st century is whether productive war is currently mutating into a new form.