"Scholars of international politics have tended to focus on the mean of foreign policies rather than the variance. In this innovative and important book, Mattiacci brings theoretical clarity and methodological firepower to the study of volatility in international politics, showing how changes in power and domestic competition combine to produce inconsistent shifts in foreign policy. A must-read for anyone interested in the turbulent era we live in." --Joshua D. Kertzer, Professor of Government, Harvard University "Some states settle into consistent patterns of conflict and cooperation. Others shift between those behaviors in unpredictable ways. By carefully measuring and rigorously explaining this variation, Eleonora Mattiacci's book provides fundamental insights about the sources of stability, change, and uncertainty in international politics." --Jeffrey A. Friedman, Associate Professor of Government, Dartmouth College, and author of War and Chance: Assessing Uncertainty in International Politics "Eleonora Mattiacci's book seeks to understand why interstate relationships are at times more volatile, exhibiting high levels of conflict and cooperation. She shows that increases in relative power and domestic political polarization jointly create volatility in relationships between rival or allied states. Her careful analyses of volatility in 36 interstate rivalries and France's withdrawal from NATO's integrated military command reveal important insights about conflict dynamics and pathways that maintain peace." --Sara B. Mitchell, F. Wendell Miller Professor, University of Iowa