In May, 1960, the Metabolist Group made a stunning debut at the World Design Conference held in Tokyo by presenting visionary proposals for future cities. Metabolism has long been understood within what Manfredo Tafuri and Francesco Dal Co have called an 'international concept of utopia' of the 1960s. Metabolism's vision of the future, however, does not neatly fit into a singular category of modernist utopia. For Japanese architects who witnessed the devastation of war in their teens, it seemed nearly impossible to imagine a technology-driven future without considering the mass destruction of the urban environment, the inevitable consequence of the very embrace of technology that post-war Japan sought as a means to brighten its future. This article situates Metabolism within Japan's specific post-war condition, which was closely tied to global Cold War geopolitics. The Cold War framework allows us to examine the dual sensibility of promise and peril inherent in Metabolism's theory and design.