Non-lethal weapons take many forms – from rubber bullets to electroshock and long-range acoustic devices – which their proponents argue are ethical, legal, and humane. Social scientists, historians, legal scholars, and activists have long challenged the use of non-lethal weapons in policing and war. Until now, little scholarly attention has been paid to the social, historical, and legal relations that animate the concept of non-lethality, nor is there a comprehensive account of how the concept has achieved social and political acceptance. Disarming Intervention tells the story of how the concept of non-lethality emerged in a series of nineteeth-century legal codes that governed the conduct of international hostilities, and how it continued to legitimate US-led armed conflicts as ethical, legal, and humane throughout the twentieth century.