Terry D. Gill is Emeritus Professor of Military Law at the University of Amsterdam and is a globally recognised authority on the law of armed conflict. He is founder and co-director of the Research Program on the Law of Armed Conflict and Military Operations (LACMO) at the Amsterdam Centre for International Law and is co-convenor of the Netherlands Research Forum on the Law of Armed Conflict and Peace Operations (LACPO). Kinga Tibori-Szabó is a post-doctoral guest researcher in the Role of Law in Armed Conflict and Military Operations (LACMO) research programme. She has been publishing and conducting research on the use of force in public international law for the past two decades and has sixteen years of experience working for international criminal tribunals. Since 2023, she has been working on criminal investigations for the United Nations in Iraq.

• Part I. Development of the Contemporary Jus ad Bellum in International Law: 1. Introduction; 2. From just war to the great war; 3. From the regulation of war to the prohibition on the use of force; Part II. Scope and Content of the Contemporary Jus ad bellum: 4. The prohibition on the use or threat of force; 5. The use of force in the un collective security system: maintenance and restoration of international peace and security through collective measures; 6. The right of self-defence: essence, function and legal foundation, requirements for exercise, scope and modalities of application; Part III. Controversies and Contested Justifications for the Use of Force: 7. Humanitarian intervention and the responsibility to protect; 8. The use of force and the rescue and evacuation of nationals; 9. Armed reprisals and the law on the use of force; 10. The use of force and weapons of mass destruction; 11. New technologies of warfare and the law on the use of force; Part IV. The Use of Force within the Wider Legal Landscape: 12. The use of force as an attribute of state sovereignty; 13. The use of force in the international commons; 14. The relationship of the law on the use of force with the law of armed conflict and human rights law; 15. International responsibility for the unlawful use of force: states, organizations, armed groups and individuals; Part V. Concluding Remarks: 16. Conclusions.

Terry D. Gill is Emeritus Professor of Military Law at the University of Amsterdam and is a globally recognised authority on the law of armed conflict. He is founder and co-director of the Research Program on the Law of Armed Conflict and Military Operations (LACMO) at the Amsterdam Centre for International Law and is co-convenor of the Netherlands Research Forum on the Law of Armed Conflict and Peace Operations (LACPO). Kinga Tibori-Szabó is a post-doctoral guest researcher in the Role of Law in Armed Conflict and Military Operations (LACMO) research programme. She has been publishing and conducting research on the use of force in public international law for the past two decades and has sixteen years of experience working for international criminal tribunals. Since 2023, she has been working on criminal investigations for the United Nations in Iraq.

• Part I. Development of the Contemporary Jus ad Bellum in International Law: 1. Introduction; 2. From just war to the great war; 3. From the regulation of war to the prohibition on the use of force; Part II. Scope and Content of the Contemporary Jus ad bellum: 4. The prohibition on the use or threat of force; 5. The use of force in the un collective security system: maintenance and restoration of international peace and security through collective measures; 6. The right of self-defence: essence, function and legal foundation, requirements for exercise, scope and modalities of application; Part III. Controversies and Contested Justifications for the Use of Force: 7. Humanitarian intervention and the responsibility to protect; 8. The use of force and the rescue and evacuation of nationals; 9. Armed reprisals and the law on the use of force; 10. The use of force and weapons of mass destruction; 11. New technologies of warfare and the law on the use of force; Part IV. The Use of Force within the Wider Legal Landscape: 12. The use of force as an attribute of state sovereignty; 13. The use of force in the international commons; 14. The relationship of the law on the use of force with the law of armed conflict and human rights law; 15. International responsibility for the unlawful use of force: states, organizations, armed groups and individuals; Part V. Concluding Remarks: 16. Conclusions.