This book explores the nature and scope of the provision requiring States to 'ensure respect' for international humanitarian law (IHL) contained within Common Article 1 of the 1949 Geneva Conventions. It examines the interpretation and application of this provision in a range of contexts, both thematic and country-specific. Accepting the clearly articulated notion of 'respect' for IHL, it builds on the existing literature studying the meaning of 'ensure respect' and outlines an understanding of the concept in situations such as enacting implementing legislation, diplomatic interactions, regulating private actors, targeting, detaining persons under IHL in non-international armed conflict, protecting civilians (including internally displaced populations) and prosecuting war crimes. It also considers topical issues such as counter-terrorism and foreign fighting.The book will be a valuable resource for practitioners, academics and researchers. It provides much needed practical reflection for States as to what ensuring respect entails, so that governments are able to address these obligations.