This chapter describes the importance of studying wartime displacement, outlines several key questions that motivate the book, and summarizes the main arguments. It also briefly defines strategic wartime displacement and specifies the scope of the study, explaining why it confines the analysis to civil wars and why it focuses on displacement perpetuated by state combatants. It then describes what we know about displacement in war. This includes outlining existing explanations and discussing their limitations. It concludes by describing the methods and sources used in the book, summarizing its main findings, and outlining the structure of the rest of the book.