Why do some nations, initially small and insignificant, go on to build mighty empires, while most nations fail to do so? And why do those successful empire-builders always eventually lose their empires? Peter Turchin, a leading thinker in the highly technical field of population dynamics, lucidly presents for the first time an approach to understanding the world's great powers throughout history--with powerful implications for nations today.  Turchin shows how the edges of empires are the crucibles of new long-lived empires and how processes of decline inevitibly follow on a 1000 year cycle.  This sweeping work of social science culminates with a crisp declaration of the general principles of the science of history. A short final section considers Tolstoy and free will in a world of historical cycles, and includes an incisive look at the U.S. now.