In this article, the authors contend that the canonical narrative about civil society’s efforts to discipline warfare during the mid-nineteenth century - a narrative of progressive evolution of Enlightenment-inspired international humanitarian law (IHL) - does not withstand scrutiny. On the basis of archival work and close reading of protocols, they argue that European governments codified the laws of war not for the purpose of protecting 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. They 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 into the bottle. Specifically, they propose that it was the Franco-Prussian War of 1870 - 1871 and the subsequent short-lived, but violent, rise of the Paris Commune that prompted governments (more than any other war during this formative era of international law) to adopt the Brussels Declaration of 1874, the first comprehensive text on the laws of war. The new law not only exposed civilians to the war's harms, but also supported the growing capitalist economy by ensuring that market interests would be protected from the scourge of war and the consequences of defeat. The laws of war, in this formative stage, were more about restoring the political and economic order of Europe than about wartime.