Book excerpt: This important and unique volume begins with seven essays that discuss the contemporary challenges to implementing international humanitarian law. Its second and largest section comprises 263 entries covering the vast majority of IHL concepts. Written by a wide range of experts, each entry explains the essential legal parameters of a particular element of IHL, while offering practical examples and, where relevant, historical considerations, and supplying a short bibliography for further research. The starting point for the selection were notions arising from the Geneva Conventions, the Additional Protocols, and other IHL treaties. However, the reader will also encounter entries going beyond the typical scope of IHL, such as those related to the protection of the natural environment and animals, and entries that, in addition to an IHL perspective, discuss relevant issues through the lens of human rights law, refugee law, international criminal law, the law on State responsibility, national law, and so on. The editors have also attempted to take into account certain concepts that have no direct foundation in IHL, but that are commonly used in mass media and politics, or generate wide interest in contemporary society, such as drones, economic warfare, cyber warfare, sniping, targeted killings, transitional justice, terrorism, and many other topics. The Companion to International Humanitarian Law offers a much-needed tool for both scholars and practitioners, supplying information accessible enough to enable a variety of users to quickly familiarise themselves with it and sufficiently comprehensive to be a source for reflection and further research for more demanding users. Its aim is to facilitate the practical application of IHL, and be of use to a wide audience interested in or confronted with IHL, ranging from professionals in humanitarian assistance and protection in the field, legal officers and advisers at the national and international level, trainers, academics, scholars, and students.