This chapter introduces the law of war crimes including: its historic development, common legal issues such as identifying an armed conflict, and the specific offences constituting war crimes. As for the historic emergence of war crimes law, the chapter looks at the evolution of humanitarian law – on which war crimes law is based. The chapter discusses the key principles of humanitarian law (distinction, proportionality, etc), the challenges of regulating warfare, the emergence of individual criminal responsibility (i.e. war crimes), and the evolution of war crimes in non-international armed conflicts. As for ‘armed conflict’, the chapter discusses common challenges in identifying the character of the armed conflict (international or non-international), for example in situations of invitation, national liberation, proxy forces, and transnational conflict. The chapter reviews the requirements to qualify as an armed conflict – intensity of the conflict and organization of the parties. It then reviews specific illustrations of war crimes, including: crimes against non-combatants (killing, sexual violence, experiments, and so on); attacks on prohibited targets (for example, historic monuments, hospitals, and so on); and attacks likely to inflict disproportionate civilian harm compared to the anticipated military advantage; prohibited weapons; and prohibited methods of warfare.

This chapter formulates guidance for applying the IHL proportionality rule by looking at its objectivity; the standard of the reasonable commander and the interpretation of the term ’excessive’.

This chapter contains an analysis of the practical application of the IHL proportionality rule by looking at a number of examples of factual situations.

This chapter contains an overview of the development of the IHL rule on proportionality in treaty law and a discussion of its existence as a customary IHL rule.

In addition to the IHL proportionality rule, IHL contains a number of other rules that fulfil a similar role as a standard of moderation and with a broader scope, including effects on enemy forces.

This chapter provides insight into the practical and legal context in which the proportionality rule must be applied: the targeting process; indiscriminate attacks and precautionary measures.

The aim of this chapter is to assess the different factors which comprise the IHL proportionality rule.

Introduction to the study of proportionality rule in international humanitarian law.

IHL proportionality as a principle of IHL and the manifestations of proportionality in other legal frameworks relating to the use of force.

This chapter pleads for a refocussed application of the IHL proportionality rule, tilting the balance more towards humanity; and analyses whether it needs to be clarified or changed.

This chapter explores whether animals can be considered as ‘property’ and ‘objects’ under the law of armed conflict, in particular under Article 23(g) of the 1899/1907 Hague Regulations on the Laws and Customs of War on Land and under the law of targeting codified in Additional Protocol I. The chapter concludes that Article 23(g) of the Hague Regulations and the law of targeting apply to animals which are considered as ‘property’ and as ‘objects’. Upon such classification, animals fall in the scope of the relevant rules. The legal consequence is that animals may only be lawfully attacked when they qualify as military objectives or when the harm done to them is proportionate incidental damage resulting from an attack on a military objective. In military operations short of attack, animals may only be destroyed or seized if military necessity ‘imperatively’ dictates it. The violation of these rules triggers not only state responsibility but also the criminal liability of the responsible individual(s).

Chapter 3 develops a theoretical grounding for the PDE, the solidarity rationale. Taking a cue from Philippa Foot, I situate the PDE within a larger region of morality, one structured around the concept of solidarity. I propose that our conduct is measured by a standard of human solidarity toward each other person, that is, a standard of concern and goodwill that is based on our common humanity, and that a person’s conduct is wrong when it deviates from this standard. I argue that the solidarity standard grounds more specific moral norms, including the precept of beneficence, the strict constraint against intentional harm, and the Principles of Proportionality and Due Care. Finally, I argue that the normative foundation for the solidarity standard is the dignity of human beings.

According to the PDE, there is a strict moral constraint against bringing about serious evil (harm) to an innocent person intentionally, but it is permissible in a wider range of circumstances to act in a way that brings about serious evil incidentally, as a foreseen but nonintended side effect. In Chapter 1, I discuss the key terms in this definition and I distinguish between an absolutist version of the PDE and a nonabsolutist one. I then introduce two principles that help guide agents when they foresee their conduct will cause incidental harm: the Principle of Proportionality and the Principle of Due Care. Finally, I describe the role of the PDE in just war theory and international humanitarian law, and I set out the plan for the remainder of the book.