The authors investigate the timing of insurgents’ use of terrorism within the context of wider-scale warfare. Unlike the great wars found in modern history, the dominant form of warfare in recent years has become internal. The main actors are non-state groups seeking to replace an existing political order through violent means. Terrorism, especially indiscriminate attacks on unarmed civilians, has been an important component of these groups’ tactical repertoires. The purpose of this study is to explore variations in the timing of insurgents’ use of terrorism within the context of war. The authors draw on the largely separate literatures on terrorism and warfare as well as complementary sources of data on terrorist events, insurgent groups, and various forms of armed conflict. The product of this analysis is a mapping of the frequencies of terrorist attacks over time and the identification of these attacks as occurring during the beginning, middle, or ending stages of wider-scale warfare. This is followed by in-depth discussions of the insurgent groups whose use of terrorism matches each of these patterns as well as the contexts within which these groups operate. Readers of this book will include students, scholars, policy-makers, members of the military, and the general public.