Chapter 1 introduces the book’s central research question and rationale. It highlights the growing prevalence of Islamist civil wars. The chapter underscores the urgent need to understand how these conflicts can be effectively ended and resolved, pointing to the lack of systematic scholarly attention to this issue. The book examines whether – and why – Islamist civil wars are more difficult to end than other conflicts, and to what extent they can be resolved. Developing a bargaining explanation, we suggest that Islamist civil wars are especially intractable because they are embedded in a particular strategic environment, which increases uncertainties about the parties’ resolve and capabilities. Understanding what makes Islamist civil wars so challenging is necessary to identify what can be done to resolve and end them. The chapter outlines the book’s main arguments and findings, including the empirical focus and cases to be explored, setting the stage for the chapters that follow.