The article explores the demise of the ‘colonial war’ category through the employment of French colonial troops, under the 1918 armistice, to occupy the German Rhineland. It traces the prevalence of – and the anxieties underpinning – antebellum doctrine on using ‘Barbarous Forces’ in ‘European’ war. It then records the silence of postbellum scholars on the ‘horror on the Rhine’ – orchestrated allegations of rape framed in racialized terms of humanity and the requirements of the law of civilized warfare. Among possible explanations for this silence, the article follows recent literature that considers this scandal as the embodiment of crises in masculinity, white domination, and European civilization. These crises, like the scandal itself, expressed antebellum jurisprudential anxieties about the capacity – and implications – of black soldiers being ‘drilled white’. They also deprived postbellum lawyers of the vocabulary necessary to address what they signified: breakdown of the laws of war; evident, self-inflicted European barbarity; and the collapse of international law itself, embodied by the Versailles Diktat treating Germany as a colonial ‘object’, as Schmitt lamented. Last, the article traces the resurgence of ‘colonial war’. It reveals how, at the moment of collapse, in the very instrument embodying it, the category found a new life. Article 22(5) of the League of Nations Covenant (the Covenant) reasserted control over the colonial object, furnishing international lawyers with a new vocabulary to address the employment of colonial troops – yet, now, as part of the ‘law of peace’. Reclassified, both rule and category re-emerged, were codified, and institutionalized imperial governance.