A brief introduction proposes the construct of generation (as outlined by Hungarian sociologist Karl Mannheim) to understand continuity and change in Japan across the historical watershed of World War II. Although generation appears frequently in other national historiographies, its application to the Japanese case is often casual and unsystematic. This generational biography illuminates the social bonds and epistemological unconscious that cohered Japanese human scientists active from the 1930s through the 1960s (the "transwar" period). In addition to sharing a chronological moment, these scholars jointly located the basis of legitimate knowledge in the claim of objectivity. They understood objectivity as faith in a universal, disinterested truth accessed by scientific methods. The career of Izumi Seiichi, who was widely acknowledged as Japan's leading transwar fieldworker, functions as an organizing principle for exploring the mentalities, activities, and influence of the group referred to as the "men of one age" or the "field generation."

The first chapter of the book situates the men of one age in historical context by tracing the co-emergence of a specific vision of objectivity as the foundation of a transnational consensus regarding the nature of legitimate knowledge, and a human science tradition grounded in the model of independent, immersive fieldwork commonly associated with British social anthropologist Bronisław Malinowski. During the age of empire, Japan's universities, the state, and the military generously sponsored fieldwork with the goal of collecting information that might help to pacify and exploit subjugated populations. Ultimately, the duration of control was too short to apply academic findings to policy in much of Japan's imperial territory. However, this chapter shows the ideological significance of racial science research through case studies of Keijō Imperial University student Izumi Seiichi's first field projects in colonial Korea (among the Jeju islanders) and Manchukuo (among the Oroqen and Goldi communities).

This chapter traces the development of group fieldwork during World War II. The challenges of operating alone in an unfamiliar war zone moved Japanese human scientists to shift to a research model of multidisciplinary teams collaborating on short-term survey projects serving the aims of the government and military. In 1938 Izumi helped to organize a pioneering group study in the Japanese puppet state in the Mongol lands (Mōkyō). He next coordinated an expedition of hundreds to Japanese-occupied New Guinea. These ventures brought his colleagues together as a generation. They united against the hardships of working among hostile peoples on violent frontiers, while sharing a sense of adventure among "exotic" research subjects and enjoying masculine sociability. By presenting the thrills and threats of fieldwork to a curious public, they established the value of human science and laid the foundations of their postwar influence over national identity.

The Allied victory in World War II appeared to prove the "objective" truth of the ideology of modernization. This bundle of ideals, including democracy, capitalism, and peace, was vaunted by the United States as characteristically American and as evidence of U.S. superiority. The U.S. occupation of Japan offered an opportunity to prove the universal truth of modernization through its implementation in a radically different context. The decision not to prosecute Japanese scholars as war criminals set the stage for an American-Japanese intellectual partnership that rehabilitated Japan's wartime research, positioned the men of one age at the pinnacle of postwar academia, and created a transnational scientific community that supported U.S. hegemony in the Cold War era. This chapter examines how American and Japanese human scientists worked together in the field to replace an epistemology devoted to justifying imperialism with a new model of knowledge grounded in the values of modernization.

After 1945, culture, broadly understood as learned social behavior, emerged as the primary variable of study for Japanese human scientists. "Culture" sought to subsume "race," which was compromised by its imperial-era baggage, but it nonetheless retained many chauvinistic and teleological assumptions. Set during the U.S. occupation, this chapter looks at three institutions through which Izumi and the men of one age entrenched culture as an objective construct and promoted the "cultural nation" as a domestic shorthand for modernization. UNESCO (the United Nations Educational, Social, and Cultural Organization) sponsored research on topics including the predicament of resident (Zainichi) Koreans and discrimination against foreigners in Japan. The Japanese Society of Ethnology cohered the national academic community through conferences, journals, encyclopedias, and other projects involving the study of culture. The University of Tokyo created the nation's first cultural anthropology department and major, facilitating the training of students in objective fieldwork.

This chapter focuses on occupation-era research projects independently organized by Japanese scholars. Group studies sought to align postwar Japan's ethnocultural and territorial boundaries through field research on marginal populations. In the summer of 1950 Izumi organized a multidisciplinary team of scholars to work on Tsushima. Situated in the strait dividing Japan and Korea, this island was represented as a step-stone between the two linked polities during the colonial period. After World War II, with sovereignty over the island uncertain, Japanese fieldworkers sought objective proof that its people were, and had always been, exemplary members of the nation. Following this venture, human scientists traveled north to Hokkaido, where they studied the indigenous Ainu population to uncover its essential belonging in the Japanese nation-state. Beyond their contribution to knowledge of "Japaneseness," these field expeditions trained and united the men for their postwar role as spokesmen of national identity.

Through a case study of Izumi's first field project outside Asia, this chapter examines how Japanese human scientists harnessed the production of knowledge abroad to the construction of national identity at home. Funded by a UNESCO research grant, Izumi ventured to Brazil, then home of the world's largest Japanese diaspora. He intended to study the Shindō Renmei crisis, a series of terrorist incidents by emigrants and their descendants who refused to acknowledge Japan's defeat in World War II. A few years later, Izumi returned to Brazil to study assimilation among the Japanese descent community. His work helped to create the new ethnic category of Nikkei (persons of Japanese ancestry outside Japan). In his hands, the emerging field of Nikkei studies came to validate an immanent and immutable Japanese inclination toward the values of modernization: democracy, capitalism, and peace.

This chapter considers the last, best-known phase of Izumi's career, as the leader of the University of Tokyo Scientific Expedition to the Andes (1958–1969). In the 1960s fieldwork in developing states never before studied by Japanese scholars helped to shift Western perceptions of Japan from the object to the agent of knowledge production. Izumi's findings at the site of Kotosh in Peru rewrote the chronology of pre-Columbian history, while his archaeological methods anticipated those adopted decades later by European and American scholars. His research also transformed the Inca empire into a consumer frenzy in Japan. Myriad exhibitions, photographs, films, television programs, travel guides, and other media technologies ignited the "Inca boom," as it was known in its day. Pre-Columbian history offered a foil for the articulation of an ideology of Japanese exceptionalism (Nihonjinron): a new vision of national identity appropriate for a rising superpower.

This chapter discusses 1968 as a revolution marking the demise of the objectivity paradigm cohering the field generation from the 1930s to the 1960s. Almost all research on the student movement of 1968 has adopted the perspective of its youthful activists, whose lives were mostly left little changed. By looking at events from the perspective of the men of one age, this chapter highlights a seismic shift in the understanding of valid knowledge. By the 1960s Izumi and his fellow transwar human scientists were themselves critical of objectivity and its constituting values associated with modernization. Ironically, it was they who mounted the challenge that students at the University of Tokyo took up to force the older generation and their vision of legitimate epistemology from power and prominence. This chapter ends by tracing the entrenchment of new schematics of credible knowledge (subjectivity, Nihonjinron, postmodernism, etc.) through the present.