In ‘Degeneration’ (1892), Max Nordau included Émile Zola in his theory that fin-de-siècle artists were a danger to society. According to Nordau, the ‘false science’ in Zola’s Naturalist novels would erode social progress in their alleged preoccupation with disease, sexual deviancy and amorality. This article proposes that degeneration is, however, a valuable lens to understand Zola’s novel ‘La Débâcle’ (1892). The work depicts a sickly Napoleon III during the Franco-Prussian War (1870–71), whose illness is metonymised with France’s politics, history and nationhood. In portraying the human body as a site of morality and coupling it with notions of illness and cure, this article demonstrates the capacity of Zola’s literary-medical aesthetics to acknowledge the body’s wider cultural and sociological importance.