In Chapter 4, the Iran–Iraq War (1980–88) serves as a case-study to test (and ultimately refute) a purely enforcement-based formalization of belligerent reprisals. In the field of chemical warfare, reciprocity and enforcement are shown to converge (rather than exclude each other) in the operationalization of belligerent reprisals. Reciprocity is seen as inspiring both the purposes associated with the measure (restoring the balance of rights and obligations and countering unlawful military advantage) and the specific traits that it would take (in-kind breach). In the "war of the cities", belligerents resorted to reprisals with purposes that cannot be encapsulated in the enforcement paradigm. These included the function of ensuring equality of opportunities (as a form of negative reciprocity) and that of strengthening, enacting and agreeing on new standards of conduct when the specific content of applicable rules was not clear or settled (as an aspect of positive reciprocity). As a result, belligerent reprisals appear as a highly flexible tool by which parties to an armed conflict bargain, approve or refuse, and police the concrete legal framework governing wartime interactions.

This chapter discusses the emergence of crimes against humanity, the main definitional features, and the most important jurisprudence on crimes against humanity. The chapter reviews historic references, the Nuremberg Charter, and evolution through international jurisprudence. The chapter examines the meaning of ‘widespread or systematic attack directed against a civilian population’, including the controversy over the meaning of ‘civilian’ and the many controversies about the ICC Statute Article 7 requirement of a ‘state or organizational policy’. The chapter reviews the jurisprudence on the prohibited acts (also referred to as ‘inhumane acts’), including murder, extermination, enslavement, deportation, forcible transfer, imprisonment, torture, rape, sexual slavery, enforced prostitution, forced pregnancy, enforced sterilization, other sexual violence, persecution, forced disappearance, apartheid, and other inhumane acts.

This chapter discusses the scope of civilian protection in light of considerations of military necessity, with particular emphasis on area bombardments and strategic air power.