In this academic but very readable work, the author tries to shed light on the contemporary meaning and legal definition of the concept of ‘Non-International Armed Conflict’, which was originally created to cover situations of ‘classical’ Civil Wars. In this book, Haeck tries to answer the question when a certain situation can be described as being a ‘Non-International Armed Conflict’. He analyses the answers that have been given by the international case-law and doctrine and creates a working-definition that can be used to determine if a situation can be classified as a Non-International Armed Conflict. Subsequently, he sheds light on the possible reasons one might have to classify something as an Armed Conflict – or not. To clarify this theoretical and abstract exercise, the author applies his theoretical framework to three contemporary case-studies. This short but heavily researched book can be an excellent starting point for everyone who is interested in the legal framework regulating the law of Armed Conflict or anyone who is eager to understand what might drive the relevant stakeholders to classify a certain situation as an Armed Conflict or not.