Turchin argues that the key to the formation of an empire is a society’s capacity for collective action. He demonstrates that high levels of cooperation are found where people have to band together to fight off a common enemy, and that this kind of cooperation led to the formation of the Roman and Russian empires, and the United States. But as empires grow, the rich get richer and the poor get poorer, conflict replaces cooperation, and dissolution inevitably follows. Eloquently argued and rich with historical examples, offers a bold new theory about the course of world history with implications for nations today.