In 1996, the International Committee of the Red Cross, alongside a range of renowned experts, embarked upon a major international study into current state practice in international humanitarian law in order to identify customary law in this area. This book is the result of that study, a comprehensive analysis of the customary rules of international humanitarian law applicable in international and non-international armed conflicts. Given that important treaties in this area have not yet been universally ratified, this is a publication of major importance, carried out at the express request of the international community. In so doing, this study identifies the common core of international humanitarian law binding on all parties to all armed conflicts.