This book began as two seminar papers, written in 2002 during my first year of graduate school at Columbia University. In those papers, I set out to explore whether and how international law influences the behavior of belligerents during wartime – in particular, during civil wars. Most research on inter- national law had focused on its role in international economic relations, but I was interested in whether international law could have any impact on the behavior of actors whose security was threatened during wartime, and, if so, why some actors might be more susceptible to the influence of international law than others. The project changed considerably over the years – becoming a broader exploration of the dynamics of civil war violence – as it morphed from seminar papers into dissertation research, and ultimately into this book. But driving the project has always been a curiosity about the impact of international legal standards on wartime behavior and the conditions under which actors are willing and able to limit their use of violence.