Pacific islands such as Japan are often unduly represented as isolated places. Land-centric biases obscure the ocean’s significance as an economic space and an ecological catalyst of historical change. With fluctuating currents, prolific upwellings, seasonal winds, and migrating animals, the ocean around Japan consists of places and depths that attracted human interest at different moments in time and invited geopolitical confrontations of various kinds. Awash in nutrient-rich currents, the Japanese archipelago is intimately entangled with the Pacific as an ecosystem, an economic space, and a contested frontier. What, then, if we were to rethink modern Japanese history as embedded in this oceanic world?

This dissertation offers a metabolic perspective on the archipelago’s radical geopolitical reorientation in the nineteenth century, enmeshed in a rapidly changing oceanic context. Overshadowed by the classical narratives of maritime prohibitions, “national seclusion” and a cultural aversion from the sea, Japan’s material and intellectual connections with the ocean have been downplayed in the past. Shifting the focus to the archipelago’s Pacific outskirts reveals the ocean as an integral part of an amphibious economic space. Japan’s Pacific rim was dominated by the fast and nutrient-rich Kuroshio or “black stream,” a warm current that meanders between the Philippines, Taiwan and Japan. The current allocates nutrients, regulates the climate, and, until the late nineteenth century, defined the scope of the navigable realm. If the Kuroshio’s bent path represented the boundary of ‘Japan’ in the early modern period (1600–1868), with the emergence of pelagic sailing and steam shipping, its interstices became the Kuroshio Frontier.

Putting the vernacular geographies of maritime localities into a conversation with intellectual debates on geopolitics, I examine the changing meanings the ocean we now call “the Pacific” assumed for those who traveled and inhabited it, and for those who observed it from afar. The construction of Japan’s Pacific since the 1780s stood in dialogue with geopolitical transformations offshore, beginning with castaway reports from lands beyond the limits of regular shipping, continuing with illicit offshore mingling between fisherfolks and Atlantic whalers in the so-called “Japan Ground,” and culminating with the Tokugawa shogunate’s establishment of an experimental colony in the Bonin or Ogasawara Islands in 1861. Fears of foreign incursion informed maritime defense strategies, while fantasies of adventure and discovery inspired private initiatives to set out and colonize the islands of the ocean frontier despite legal and physical obstacles.

I argue that the expansion to island colonies across the Kuroshio Frontier in the late nineteenth century was a formative moment for concepts, ideologies and networks that proved central in the Japanese empire’s subsequent mode of expansion. An oceanic focus on Japan’s nineteenth century therefore not only bridges temporal divisions of “early modern” and “modern,” but it also reveals the Asia-Pacific as a pelagic region structured in a historically conditioned geography of marine economy, shipping lanes, as well as animate and inanimate resources. Understanding this space as a contested frontier region brings people, places and environmental transformations to the fore that are otherwise dismissed as peripheral. The Bonin Islanders, Pacific migrants that came to the Kuroshio Frontier during the whaling boom of the 1830s, became agents of knowledge when they transferred technical and technological knowledge to the Japanese. Likewise, networks of ‘South Sea’ colonization in the nineteenth century spanned those frontier islands that had emerged from the rush to the Kuroshio frontier. In sum, Japan’s oceanic expansion transcends the conventional divides of early modern and modern, shogunal and imperial, insular and global. It raises questions of periodization and ethnicity that challenge the spatial and temporal boundaries of “modern” Japan itself.

Unlike terrestrial frontiers of the early modern world, the Kuroshio Frontier so far evades closure. With most living resources reduced to a fraction of pre-industrial levels, the frontier keeps expanding vertically today, towards ever-deeper deposits of oil and rare earth minerals below the ocean’s surface. Once again, the frontier’s seemingly inexhaustible resources feed hopes for an escape from a resource impasse, accentuating international competition for maritime space in the twenty-first century. With this dissertation, I aim to offer an explanation for the emergence of the ideological and economic mechanisms that drive this expansion today, and thereby, to shed light on the cultural biases behind the crises of the dawning Anthropocene.