Conflict is not distributed equally around the world. Rather, as this book explains, the globe is broken up into zones of peace and hostility. States tend to cluster regionally according to type -- mature democracies, transforming democracies, and autocracies -- and those types interact differently when it comes to conflict. In turn, Gleditsch argues, two factors shape regional variations. First is the extent of integration, which reshapes identities, relationships, and expectations, thereby taming conflict within a dense network of regional ties. The other is the presence of stable democratic institutions, which constrains the use of force; western Europe and the Atlantic community are the obvious pioneers in both trends. Gleditsch shows how the interactions between these factors push regions closer or further away from stable peace. One implication is that democracy is a critical component of regional peace -- but international efforts at democratization in one country (say, Iraq) will not likely be successful unless the wider region is also moving in this direction. The book's one shortcoming is that its statistical bent ignores specific historical or contemporary regional cases; Europe is not even listed in the index.