An in-depth account of why countries’ treacherous foreign policies often have harmless origins, how this predicament shapes international politics, and what to do about it. The increasing unpredictability of state behavior in recent world politics is a surprising development. The uncertainty that results intensifies conflict and stymies trust. In Volatile States in International Politics, Eleonora Mattiacci offers the first account of this issue that investigates which states have been volatile and why. Leveraging statistical techniques and archival data in a probing analysis of rivals and allies since the end of World War II, she rejects attempts at dismissing volatility as reflecting mercurial leaders or intractable issues. Instead, Mattiacci explains that a state acts in a volatile manner when its clashing domestic interests leverage power to achieve their goals on the international arena. In demonstrating states’ potential for volatile behaviors, she asks us to reconsider how much we really know about change and instability in international politics. When properly understood, she shows, volatile behavior can become less confusing for observers and potentially less dangerous. This book offers novel, evidence-based tools to cope with volatility in the global arena.