jats:titleAbstract</jats:title> jats:pIn this article, we challenge the canonical narrative about civil society’s efforts to discipline warfare during the mid-19th century – a narrative of progressive evolution of Enlightenment-inspired laws of war, later to be termed international humanitarian law. Conversely, our historical account shows how the debate over participation in international law-making and the content of the law reflected social and political tensions within and between European states. While the multifaceted influence of civil society was an important catalyst for the inter-governmental codification of the laws of war, the content of that codification did not simply reflect humanitarian sensibilities. Rather, as civil society posed a threat to the governmental monopoly over the regulation of war, the turn to inter-state codification of IHL also assisted governments in securing their authority as the sole regulators in the international terrain. We argue that, in codifying the laws of war, the main concern of key European governments was not to protect civilians from combatants’ fire, but rather to protect combatants from civilians eager to take up arms to defend their nation – even against their own governments’ wishes. We further argue that the concern with placing ‘a gun on the shoulder of every socialist’ extended far beyond the battlefield. Monarchs and emperors turned to international law to put the dreaded nationalist and revolutionary genies back in the bottle. These concerns were brought to the fore most forcefully in the Franco-Prussian War of 1870–1871 and the subsequent short-lived, but violent, rise of the Paris Commune. These events formed the backdrop to the Brussels Declaration of 1874, the first comprehensive text on the laws of war. This Declaration exposed civilians to war’s harms and supported the growing capitalist economy by ensuring that market interests would be protected from the scourge of war and the consequences of defeat.</jats:p>