The St Petersburg declaration, signed in 1868, is a milestone in the history of warfare and humanitarian law, as it prohibits the use of explosive bullets, which are considered to cause unnecessary suffering. As this article shows, the framing of this declaration that put suffering at its centre, as well as the development of the humanitarian movement, favoured the birth of a new field of expertise: wound ballistics. The wars that broke out after the declaration was signed are the subject of intense scrutiny, while the advances in weaponry, and notably, the creation by the British of a new expansive bullet, provided physicians with new fields of investigation. Numerous experiments have attempted to reproduce the effects of bullets on different materials, including corpses. Based on numerous medical reports and publications, as well as military archives from France and the United Kingdom, this investigation critically examines the notion of pain, its assessment and its use in the monitoring of war violence. It argues that, paradoxically, the greater attention paid to suffering has resulted in a need to objectify pain. This rationalisation and the quest for the quantification of suffering have not been without bias and have shifted attention away from care and treatment.