The Law in War A Concise Overview This book provides a comprehensive yet concise overview of the law that regulates armed hostilities between States, and between States and non-State groups. The text explains the conditions that result in the applicability of international humanitarian law, and then subsequently addresses how the law influences a broad range of operational, humanitarian, and accountability issues that arise during military operations. Each chapter provides a clear and comprehensive explanation of humanitarian law, focusing especially on how it impacts operations. The chapters also highlight both contemporary controversies in the field and potentially emerging norms of the law. This book is an ideal companion for students studying international humanitarian law and military and civilian attorneys engaged in humanitarian law practice, as well as an excellent introduction for students and practitioners of public international law and international relations. Geoffrey Corn is the Vinson & Elkins Professor of Law at the South Texas College of Law Houston. Prior to joining the South Texas faculty in 2005, Professor Corn served in the U.S. Army for 21 years, retiring in the rank of Lieutenant Colonel. Following retirement from active duty, Professor Corn served an additional year as the Army’s senior civilian law of war expert in the Office of the Judge Advocate General and Chief of the Law of War Branch in the International Law Division. Ken Watkin served for 33 years in the Canadian Forces, including four years as the Judge Advocate General. In 2002 he was appointed to the Order of Military Merit, in 2006 a Queen’s Counsel, and in 2010 he received the Canadian Bar Association President’s Award. Ken was responsible for providing operational law advice regarding Canada’s military operations post-9/11, and worked as government counsel for various inquiries arising from the 1994 Rwandan genocide. Since his retirement in 2010, he has served as a foreign observer to the Israeli Independent Commission investigating the 2010 Gaza blockade incident, and as the Charles H. Stockton Professor of International Law at the United States Naval War College. He is the author of Fighting at the Legal Boundaries: Controlling the Use of Force in Contemporary Conflict (Oxford University Press, 2016), which was awarded the 2017 Francis Lieber Prize by the American Society of International Law. Jamie Williamson is the executive director of the International Code of Conduct for Private Security Providers Association. He previously worked with the International Committee of the Red Cross in a number of legal, operational, and managerial positions in Geneva, Washington, D.C., and southern Africa. He also served from 1996–2005 with the UN ad hoc international criminal tribunals in Tanzania and the Netherlands, and with the Special Court for Sierra Leone. Jamie is on the faculty of the American University’s Program of Advanced Studies of the Academy on Human Rights and Humanitarian Law. The Law in War A Concise Overview Geoffrey Corn Ken Watkin Jamie Williamson First published 2018 by Routledge 2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN and by Routledge 711 Third Avenue, New York, NY 10017 Routledge is an imprint of the Taylor & Francis Group, an informa business © 2018 Geoff Corn, Ken Watkin, Jamie Williamson The right of Geoff Corn, Ken Watkin, Jamie Williamson to be identified as authors of this work has been asserted by them in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data Names: Corn, Geoffrey S., author. | Watkin, Kenneth, author. | Williamson, Jamie (Jamie A.), author. Title: The law in war : a concise overview / by Geoffrey Corn, Ken Watkin, Jamie Williamson. Description: Abingdon, Oxon [UK]; New York, NY : Routledge, 2018. | Includes bibliographical references and index. Identifiers: LCCN 2018002753 | ISBN 9781138910478 (hbk) | ISBN 9781138910485 (pbk) | ISBN 9781317436201 (epub) | ISBN 9781317436195 (mobipocket) Subjects: LCSH: War (International law). | Humanitarian law. | War victims—Legal status, laws, etc. | Prisoners of war—Legal status, laws, etc. | Detention of persons. | War crimes. Classification: LCC KZ6355.C67 2018 | DDC 341.6—dc23 LC record available at https://lccn.loc.gov/2018002753 ISBN: 978-1-138-91047-8 (hbk) ISBN: 978-1-138-91048-5 (pbk) ISBN: 978-1-315-69340-8 (ebk) Typeset in Galliard by Florence Production Ltd, Stoodleigh, Devon, UK Contents Foreword List of abbreviations 1 2 xi xiii Introduction 1 International humanitarian law application 1 Introduction 2 Origins of the conflict classification paradigm 2.1 The triggers—Common Articles 2 and 3 5 2.2 The existence of an armed conflict 7 2.3 The nature of the armed conflict 11 3 The impact of the 1977 Additional Protocols 4 A few wrinkles 4.1 External intervention in an internal armed conflict 15 4.2 Straddling the armed conflict threshold 16 4.3 Transnational armed conflicts? 17 4.4 The intersection of international humanitarian law and international human rights law 18 5 Conclusion 4 4 4 Non-international armed conflict 1 Introduction 2 The non-State actor threat 2.1 Internal conflict 28 2.2 Transnational threats 29 2.3 Crime and non-State actor conflict 30 3 The legal framework 3.1 Treaty law 32 3.2 Customary and soft law 34 3.3 The role of human rights law 35 13 15 20 26 26 28 32 vi Contents 4 5 3 4 Classifying conflict with non-State actors 4.1 Non-State actors and international armed conflict 37 4.2 Non-State actors and non-international armed conflict 39 4.3 The non-international armed conflict threshold 41 4.4 Non-State actors, self-defense and armed conflict 44 Conclusion 36 45 The status of individuals in armed conflict 1 Introduction 2 International armed conflict 2.1 Regulating combatant status 53 2.1.1 Early codification 53 2.1.2 In the aftermath of World War II 56 2.1.3 Additional Protocol I 59 2.2 Unlawful or unprivileged belligerents 62 2.3 Civilians 64 3 Non-international armed conflict 4 Miscellaneous categories 4.1 Child soldiers 69 4.2 Mercenaries 69 4.3 Journalists 70 5 Conclusion 52 52 53 Dealing with civilians, wounded, and sick 1 Introduction 2 Protecting civilians 2.1 Who is a civilian? 79 2.1 Protection from the effects of attack 79 2.3 Protecting civilians from maltreatment: the humane treatment obligation 79 2.4 Building on humane treatment: the spectrum of civilian protection 80 2.4.1 Civilian protection in non-international armed conflicts 80 2.4.2 Civilian protection in international armed conflicts 82 3 Protecting civilian property 4 Protecting the wounded and sick 4.1 Protecting the wounded and sick in international armed conflicts 89 77 77 78 66 68 71 87 88 Contents 5 5 6 4.1.1 Handling the wounded and sick 91 4.1.2 Casualties 92 4.1.3 The distinctive emblem: the symbol of special protection 93 4.1.4 Personnel aiding the wounded and sick 95 4.1.5 Medical units, establishments, and transportation 97 4.1.6 Facilities and vehicles 97 4.1.7 Medical aircraft 99 4.2 Protecting the wounded and sick in non-international armed conflicts 102 Conclusion vii 103 Prisoners of war and other detainees 1 Introduction 2 Prisoners of war 2.1 And who decides? 119 2.2 Retained persons 120 2.3 Civilians 120 2.4 Unprivileged belligerents 121 3 Detainee treatment 3.1 Location and duration of detention 122 3.2 Criminal liability 123 3.3 Fundamental protections 125 3.4 Protections related to escape 128 3.5 Oversight and the protecting power 129 4 Detention in non-international armed conflicts 4.1 The need and authority to detain 130 4.2 Sources of authority 131 4.3 Customary incident of any armed conflict? 133 4.4 Non-international armed conflict detention and humanitarian protection 136 4.5 Detention review process 136 4.6 Detainee treatment 137 5 Conclusion 113 113 114 Targeting 1 Introduction 2 The law of targeting 3 Targeting persons 4 Targeting objects 142 142 143 145 147 122 130 137 viii Contents 4.1 4.2 4.3 4.4 5 6 7 Military objects 147 Military action and war sustaining 149 Military advantage 150 Targeting precautions 151 4.4.1 General 151 4.4.2 Excessive collateral casualties and damage 152 Miscellaneous issues 5.1 Drones 155 5.2 Rules of engagement 155 5.3 Investigations 156 Conclusion Weapons, means, and methods 1 Introduction 2 Weapons and the law 3 The employment of weapons 3.1 General 164 3.2 Superfluous injury and unnecessary suffering 165 3.3 Indiscriminate weapons 167 3.4 Environmental protection 168 3.5 Weapons reviews 170 4 Specific weapons 4.1 Expanding bullets 171 4.2 Mines, booby-traps, and improvised explosive devices 172 4.2.1 Anti-personnel mines 172 4.2.2 Booby-traps 174 4.2.3 Improvised explosive devices 174 4.3 Cluster munitions 175 4.4 Poison, chemical, bacteriological, and nuclear weapons 176 4.4.1 Poison weapons 176 4.4.2 Chemical weapons 176 4.4.3 Bacteriological and biological weapons 177 4.4.4 Nuclear weapons 177 4.5 Cyber weapons 178 4.6 Autonomous weapons 179 4.7 Nanotechnology 180 5 Tactics 5.1 Treachery 181 5.2 Capture rather than kill 183 6 Conclusion 155 156 162 162 162 164 171 180 184 Contents 8 9 ix Neutrality and naval warfare 1 Introduction 2 An introduction to the sources of law applicable during naval warfare 3 The law of the sea: classification of and conduct within the world’s waters 3.1 Status of vessels and aircraft under international law 196 4 The law of neutrality 4.1 An introduction to neutrality 198 4.2 The rights and obligations of neutral States 199 4.3 The rights and obligations of belligerent States regarding interaction with neutral States 200 4.4 Special rules related to neutral shipping 201 5 Applicability of international humanitarian law during naval warfare 6 Naval warfare: special tactics 6.1 Blockade 204 6.2 Naval exclusion zones 206 6.3 Submarine warfare 206 6.4 Sea mines 207 7 Protecting the wounded, sick, and shipwrecked during naval warfare 8 Conclusion 193 193 Air 1 2 3 4 216 216 217 219 221 5 6 and missile warfare Introduction Theory, doctrine, and the use of airpower Airpower: a unique challenge Aerial warfare 4.1 Status of aircraft and aircrew 221 4.1.1 Military aircraft and aircrew 221 4.1.2 Civilian aircraft and aircrew 222 4.1.3 Protected status 223 4.2 Conduct of operations 224 4.3 No-fly zones and aerial blockades 225 4.3.1 No-fly zones 225 4.3.2 Aerial blockades 226 Missile warfare Conclusion 194 195 198 203 204 208 210 226 227 x 10 11 12 Contents Command responsibility 1 Introduction 2 A settled principle 3 Conditions for establishing command responsibility 3.1 Superior–subordinate relationship 236 3.2 The knowledge requirement 238 3.3 To prevent and to punish 240 4 Manifestly illegal orders and superior orders 4.1 What is manifestly illegal? 242 4.2 The defense of superior orders 244 5 Conclusion 233 233 234 236 International justice and compliance 1 Introduction 2 International criminal tribunals 3 Hybrid courts 3.1 The Special Court for Sierra Leone 256 3.2 The Extraordinary Chambers in the Courts of Cambodia 258 4 The permanent international criminal court 4.1 Jurisdiction of the International Criminal Court 258 4.2 A gravity threshold 260 4.3 A court of last resort 262 5 Alternative compliance mechanisms 5.1 A compliance gap 263 5.2 A new compliance mechanism? 264 6 Conclusion 251 251 252 255 War crimes and accountability 1 Introduction 2 What is a war crime? 3 The grave breaches regime under international law 4 The trigger for war crimes accountability 4.1 The existence of an armed conflict 278 4.2 What constitutes a nexus? 280 5 Who can be held responsible? 6 Amnesties 7 Conclusion 272 272 273 276 278 Appendix: Article 8 of the Rome Statute Index 291 295 241 244 258 263 265 282 284 286 Foreword International humanitarian law, or the law of armed conflict, has never been more relevant than it is today. Even those with no military or legal background understand that international law imposes limits on the conduct of armed forces and organized armed groups engaged in hostilities, and requires respect for the fundamental human rights of war victims. This book is intended to contribute to a more informed understanding of this important branch of international law. In deciding to collaborate on this project, we three authors sought to leverage a variety of perspectives and experiences to this book. International humanitarian law has been a central focus of each of our professional experiences. Our collective interest in the law is therefore grounded in practical experience, but from quite different perspectives. We hope this results in not only a comprehensive overview of the law but one that is reflective of these different perspectives. We know that anyone considering this book will have the choice of many excellent options. Our goal was to provide a concise overview of international humanitarian law, one that is equally accessible to the non-lawyer as it is to the lawyer; and that is equally valuable to the practitioner as it is to the interested member of society. To that end, we have selected the aspects of the law we believe are most essential for providing such an overview. While a more extensive treatment of many of these aspects of the law would certainly have been possible, our goal was to provide an outline of the law. Nonetheless, we believe our overview is sufficiently comprehensive to substantially contribute to a meaningful understanding of how international humanitarian law actually impacts military operations. Finally, we must commend our research assistant, Andrew Culliver, who graduated with his Juris Doctor degree from the South Texas College of Law Houston in May 2017 and began his career as First Lieutenant in the U.S. Army Judge Advocate General’s Corps in January 2018. Andrew’s contribution to this book was essential in its completion, and his diligence and selflessness deserves our highest praise. It is especially meaningful for us that his efforts were so central to completing a project that will hopefully contribute to his own professional development and that of his JAG peers. Abbreviations Additional Protocol I or AP I or 1977 Protocol I Protocol (I) Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of International Armed Conflicts, 8 June 1977 Additional Protocol II or AP II or 1977 Protocol II Protocol (II) Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of International Armed Conflicts, 8 June 1977 Additional Protocol III Protocol (III) Additional to the Geneva Conventions or AP III of 12 August 1949, and Relating to the Adoption of an Additional Distinctive Emblem, 8 December 2005 AP Commentary Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949 AFRC Armed Forces Revolutionary Council (a rebel group formerly in Sierra Leone) AR Army Regulation (United States) ATACMS Army Tactical Missile System (United States) AUMF Authorization for Use of Military Force (United States) BWC Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on Their Destruction, 10 April 1972 Common Article 2 or CA2 Article 2 common to all four of the Geneva Conventions, 12 August 1949 Common Article 3 or CA3 Article 3 common to all four of the Geneva Conventions, 12 August 1949 CAT Convention Against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, 10 December 1984 xiv Abbreviations CCW Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects, 10 October 1980 CDF Civil Defense Force (a paramilitary organization that operated during the Sierra Leone Civil War) CIL Customary international law CIWS (Phalanx) Close-In Weapons System (United States) CNA Computer network attack CPL Civilian Protection Law CRC Convention on the Rights of the Child, 20 November 1989 CS gas 2-chlorobenzalmalononitrile (a component of tear gas) CSRT Combatant Status Review Tribunals (United States) CWC Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction, 13 January 1993 DoD Department of Defense (U.S.) DPH Direct participation in hostilities ECCC Extraordinary Chambers in the Courts of Cambodia EEZ Exclusive economic zone ENMOD Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques, 18 May 1977 EPW Enemy prisoners of war ERW Explosive remnants of war European Convention on Human Rights or ECHR Convention for the Protection of Human Rights and Fundamental Freedoms, 3 September 1953 EU European Union FARC Revolutionary Armed Forces of Columbia or Fuerzas Armadas Revolucionarias de Colombia Geneva Law Law attributable to the protection of victims of armed conflict 1864 Geneva Convention Geneva Convention for the Amelioration of the Condition of the Wounded in Armies in the Field, 22 August 1864 Abbreviations xv GWS or First Geneva Convention or Geneva I or GC I Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field, 12 August 1949 1906 GWS or 1906 Geneva Convention Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armies in the Field, 6 July 1906 1929 GWS Geneva Convention for the Amelioration of the Condition of the Wounded and Sick of Armies in the Field, 27 July 1929 GWS-Sea or Second Geneva Convention or Geneva II or GC II Geneva Convention for the Amelioration of the Condition of Wounded, Sick, and Shipwrecked Members of the Armed Forces at Sea, 12 August 1949 GPW or Third Geneva Convention or Geneva III or GC III Geneva Convention Relative to the Treatment of Prisoners of War, 12 August 1949 1929 GPW Geneva Convention Relative to the Treatment of Prisoners of War, 27 July 1929 GC or Fourth Geneva Convention or Geneva IV or GC IV Geneva Convention Relative to the Protection of Civilian Persons in Time of War, 12 August 1949 Hague Law Law attributable to the conduct of hostilities 1907 Hague IV Regulations or 1907 Hague Regulations or 1907 Hague Land Warfare Regulations or Hague IV or 1907 Regulations Convention (IV) Respecting the Laws and Customs War on Land and its annex: Regulations concerning the Laws and Customs of War on Land, 18 October 1907 HIMARS High Mobility Artillery Rocket (United States) HPCR Air and Missile Program on Humanitarian Policy and Conflict Warfare Manual Research Manual on International Law Applicable to or HPCR AMWM Air and Missile Warfare IAC International armed conflict ICC International Criminal Court ICCPR International Covenant on Civil and Political Rights, 16 December 1966 ICJ International Court of Justice ICL International criminal law xvi Abbreviations ICRC International Committee of the Red Cross ICTR International Criminal Tribunal for the Prosecution of Persons Responsible for Genocide and Other Serious Violations of International Humanitarian Law Committed in the Territory of Rwanda and Rwandan Citizens Responsible for Genocide and Other Such Violations Committed in the Territory of Neighbouring States, between 1 January 1994 and 31 December 1994 ICTY International Tribunal for the Prosecution of Persons Responsible for Serious Violations of International Humanitarian Law Committed in the Territory of the Former Yugoslavia since 1991 or International Criminal Tribunal for the former Yugoslavia IDF Israeli Defense Forces IED Improvised explosive device IHFFC International Humanitarian Fact-Finding Commission IHL International humanitarian law (synonymous with law of armed conflict or LOAC) IHRL International human rights law ISIS or ISIL Islamic State of Iraq and Syria or Islamic State of Iraq and the Levant JNA Yugoslav People’s Army KLA Kosovo Liberation Army LOAC Law of armed conflict (synonymous with international humanitarian law or IHL) LRM Least restrictive means (theory) MICT International Residual Mechanism for Criminal Tribunals MOOTW Military operations other than war MRLS Multiple Rocket Launch System (United States) NATO/OTAN North Atlantic Treaty Organization/Organisation du Traité de l’Atlantique Nord NEO Non-combatant evacuation operation NIAC Non-international armed conflict NOTAM Notice to airmen Abbreviations xvii Ottawa Convention or 1997 Ottawa Convention Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on Their Destruction, 18 September 1997 PFLP Popular Front for the Liberation of Palestine PLO Palestine Liberation Organization POW Prisoner of war ROE Rules of engagement 1998 Rome Statute or Rome Statute Rome Statute of the International Criminal Court, 17 July 1998 RP Retained person(s) or retained personnel RSCSL Residual Special Court for Sierra Leone RUF Revolutionary United Front (a rebel group formerly in Sierra Leone) SAS Special Air Service (United Kingdom) SBS Special Boat Service (United Kingdom) SCSL Special Court for Sierra Leone SEALs “Sea, Air, Land” special forces (United States) SROE Standing rules of engagement THAAD Terminal High Altitude Area Defense (United States) UAV/UCAV Unmanned aerial vehicle/unmanned combat aerial vehicle UN United Nations UNGA United Nations General Assembly UDHR or 1948 Universal Declaration on Human Rights Universal Declaration on Human Rights, 10 December 1948 UNSC United Nations Security Council UK United Kingdom of Great Britain and Northern Ireland US or U.S. United States USA United States Army USN United States Navy UXO Unexploded ordinance VJ Army of the Federal Republic of Yugoslavia xviii Abbreviations VRS Army of the Serbian Republic of Bosnia and Herzegovina/Republika Srpska 9/11 11 September 2001 terror attacks in the United States Introduction War has been an unfortunate part of human existence from the beginning of recorded history, despite periodic efforts to eliminate war from human relations. While the very nature of warfare is inherently chaotic, for as long as warfare has been a reality, man has tried to inject a certain degree of order. What can very generally be labeled as rules and customs of war have and remain a defining characteristic of warfare, in a very real sense the thing that distinguishes war from total chaos. These rules have taken different forms, included different content, and were derived from differing sources throughout history. But, as international law emerged as a source of regulation for relations between sovereign States, rules of war took a prominent place in the emerging body of customary international law. This was most notably the case for the nations of Europe, and to a lesser extent the new nations in North and South America that grew out of the seeds of European colonization. For centuries, a handful of highly respected international law scholars provided treatises that detailed the accepted rules of conduct in warfare. The American Civil War proved to be a transformative event in the evolution of the laws and customs of war. Unlike European nations, neither the United States nor the newly formed Confederate States of America could call on a large professional military steeped in the customs of the professional warrior. Instead, consistent with the American aversion for standing armies, this massive and brutal conflict would be fought primarily by citizen-soldiers on both sides of the battle lines. Recognizing that this rapid formation of a massive unprofessional army necessitated more concrete rules of conduct, General Henry Halleck, the commander of all Union armed forces, commissioned Professor Francis Lieber of Columbia University to draft what was in essence a code of conduct for the Union armed forces that enumerated rules of customary international law. Lieber’s effort would be issued as General Order Number 100, and known thereafter as the Lieber Code. The idea of enumerating rules of war for the force also appealed to the Confederacy, which also adopted Lieber’s Code. This initiated what is best understand as an era of codification, which progressed along two related but somewhat distinct tracks. On one track was the effort to ameliorate the suffering of victims of war, which began with the First Geneva 2 Introduction Convention of 1864, devoted to the protection, collection, and care for the wounded and sick on the battlefield. Over the next approximatly 80 years, this Geneva tradition would bear fruit in the form of multiple treaties devoted to the protection of distinct classes of war victims: the wounded and shipwrecked at sea, prisoners of war, and civilians under enemy control. These four Geneva Conventions would earn the distinct status of the only treaties universally ratified by the community of nations. On the other track were efforts to regulate the conduct of hostilities—how armies fought one another. This began modestly with a treaty banning what was at the time considered an especially pernicious weapon—the bullet that exploded upon impact. But this was a landmark treaty, for it initiated the process of developing multilateral treaty regulations related to both the means (weapons) and methods (tactics) of warfare. In 1899, and again in 1907, such regulations were adopted as part of The Hague Convention IV. Since that time, treaty law and customary law have continued to evolve, creating what is often a complex and in many ways symbiotic relationship with one another. Many rules considered customary in nature have been incorporated into specific treaty provisions; other new rules adopted in treaties have been so pervasively followed that they are today considered customary in nature, therefore binding on even non-treaty States. Other treaty rules are, as the result of rejection by non-treaty States or through reservations lodged by States upon treaty ratification, binding only on those States that have expressly agreed to them. This relationship between treaty and customary international law will be a consistent feature of the chapters that follow. Collectively, these efforts to create a body of law governing armed conflict have resulted in the creation of a body of law historically called the law of war, but today more commonly referred to as the law of armed conflict (LOAC) or international humanitarian law (IHL). These designations are synonymous in terms of the law they refer to, but as IHL is the more common characterization today it will be the primary characterization used throughout this text. One especially significant IHL evolution has been in relation to the regulation of what are known as non-international armed conflicts (NIACs). Prior to 1949, international law played little to no role in the regulation of conflicts other than those between States: so-called international armed conflicts (IACs). There were some civil wars that fell within the scope of this international legal regulation by operation of a doctrine called recognition of belligerency, whereby both parties to the conflict, because they manifested indications of statehood, were treated as States for purposes of both international legal regulation, and so that neutral States could rely in the international law of neutrality when dealing with them. For example, a number of European nations recognized the Confederate States of America as a belligerent during the American Civil War. However, this was a rare exception to the more general reality that conflicts between States and nonState belligerent groups were not considered “wars” within the meaning of international law, and therefore beyond the scope of the international laws and customs of war. Introduction 3 The International Committee of the Red Cross, the organization created by the First Geneva Convention and vested with the specific mandate to monitor compliance with the Conventions and facilitate implementation of the Conventions, sought to address this humanitarian gap during the conference called to revise the 1929 Geneva Conventions that resulted in the 1949 version of these treaties. It proposed extending application of the four Conventions to any armed conflict, whether international (inter-State) or non-international (generally understood at that time as intra-State). The assembled State delegations ultimately rejected this proposal, but did agree to include within the four Conventions a single Article imposing on parties to a NIAC the obligation to treat humanely any individual not actively participating in hostilities. The first express imposition of humanitarian regulation to NIACs, this “common article” provided a foundation for subsequent efforts to provide humanitarian constraints and obligations on parties involved in such armed conflicts, a process that continues to this day and will be addressed in Chapter 1 of this text. Another important evolution of IHL occurred in relation to accountability for violations. As will be explored, prior to World War I international law was understood as imposing obligations exclusively upon States, and not on individuals. As a result, remedies for violations of the laws and customs of war involved actions by one State directed against another. Beginning with the Treaty of Versailles, this changed. In order to enhance the effectiveness of the law, individuals were subjected to accountability for their violations of what is today IHL. This notion of individual responsibility advanced in fits and starts, but today is firmly rooted in the fabric of international criminal law (ICL). Nonetheless, there are important and complex questions abound where IHL intersects with ICL, ranging from the relationship between State and international criminal jurisdiction, to requisite criminal state of mind for transforming a violation of regulatory norms into a basis for criminal responsibility, to liability of leaders for their failure to ensure compliance with the law. All of these issues, and many more, will be addressed in the chapters that follow. Our goal is not to provide a comprehensive restatement of the law, or even a comprehensive treatise on the law. Instead, we hope to provide an accessible overview of the law, exposing the reader to the most important legal concepts, lingering and emerging areas of uncertainty, and an appreciation of how law impacts the planning and execution of military operations.