Contemporary political science has generated extensive literatures on the themes of war, civil war, contentious politics, and social movements. But these literatures are often segregated in particular subfields, like International Relations and Comparative Politics, and typically speak past each other rather than to each other. Sidney Tarrow’s War, States, & Contention: A Comparative Historical Study (Cornell 2015) offers a single, synthetic perspective on these topics. As Tarrow states, “I hope to show that the advent of war is sometimes driven by social movements; that movements often affect the conduct of war and sometimes change its directions; and that wars often trigger the rise and expansion of movements in their wake.” Few topics are more important than the ones considered in this book, and so we have invited a range of political scientists, from a variety of subfield and methodological approaches, to comment on the book.