This book examines the effects of external interventions on conflict escalation in civil wars, using data from African conflicts since the cold war. It investigates how the targets and types of external interventions affect the capabilities of the conflict parties, which lead to specific escalatory or de-escalatory effects on conflict intensity. A main contribution of this book is to test a theory of external interventions through mixed methods. It presents and uses a new dataset on external interventions with 42 conflicts that occurred in 30 countries in Africa between 1989 and 2010 and then tests the theory with four case studies and an econometric analysis. The work fills a gap in the literature by focusing on the effect of interventions on civil war intensity. There are only a few studies looking into the severity of conflict but their studies look at total conflict intensity and not escalatory or de-escalatory processes and do not focus on the specific effect of external interventions. Another contribution of this book is that it extends the operationalization of conflict to very low levels of conflict, to include civil war and low intensity levels starting the conflict period from the first battle death of these conflicts. This extension is relevant to better understand escalation on the onset and recurrence of conflict. The book is also the first to look holistically at external interventions, by considering military, economic and diplomatic interventions alongside UN and non-UN missions. This approach is closer to the realities of conflict where several types of interventions occur concurrently. This book will be of interest to student of civil wars and intra-state conflict, civil wars, peace studies, security studies and IR.