This chapter investigates whether and how the laws that govern armed conflict achieve their objective of minimizing the suffering of combatants and non-combatants alike. International humanitarian law (IHL) reflects the tensions of an international legal order that oscillates between the apologist tendency to reflect state practice and state self-interest and the utopian desire to reflect higher values of justice and human dignity. The chapter begins with a brief overview of the evolution of this body of law, the codification of which dates from the second half of the nineteenth century. It then turns to the question of terminology, analysing the political origins and legal implications of the relatively recent term ‘international humanitarian law’. The chapter focuses on two key questions. Firstly, who or what is a legitimate target during an armed conflict? Secondly, what are legitimate means of conducting armed conflict? The chapter also considers the status of nuclear weapons under international law, a topic that captures well both the possibilities and limits of IHL.