This article tells a three-layered story. First, it reexamines the impact of French geographer Yves Lacoste’s 1972 exposé on the American bombing of the Red River Delta of North Vietnam on opposition to the Vietnam War and how it was implicated in wider political debate about what Hannah Arendt saw as systemic “lying in politics.” In various reports and newspaper articles Lacoste deployed the tools of classical geography—firsthand observation, mapping, and the integrated analysis of physical and human factors—to disclose connections among law, war, and environment (or what he termed “geographical warfare”) that had a troubling political significance. Second, we explore how Lacoste’s exposé was bound up with the theme of “tropicality” (the West’s construction of “the tropics” as its environmental other), chiefly through his recourse to Gourou’s study (1936) of the delta. Lacoste showed how exotic imagery of the tropics has served as a means of opposition and critique as well as a mode of othering and Western dominance. Third, Lacoste’s critical engagement with Gourou points to the ambivalent critical impact that the Vietnam War had on Francophone and Anglophone geography during the 1970s and 1980s, yet also how interest in the idea of tropicality developed in French geography twenty years before the better known Anglophone critical literature on the subject emerged.