This study examines the development of the concept of “bushido,” or the “way of the warrior,” in modern Japan, focusing on the period between the mid-nineteenth century and the early 1930s. The popular view holds that bushido was a centuries-old code of behavior rooted in the historical samurai class and transmitted into the modern period, where it was a fundamental component of Japanese militarism before 1945. In fact, the concept of bushido was largely unknown before the last decade of the nineteenth century, and was widely disseminated only after 1900, especially after the Russo-Japanese War of 1904-5. This study argues that modern bushido discourse began in the 1880s, and was dependent on political and cultural currents relating to Japan’s modernization and the nation’s attempts to redefine itself in the face of foreign “others,” primarily China and the West. Following more than a decade of largely unquestioned thrusts towards modernization and Westernization after 1868, Japanese thinkers looked to their own traditions in search of sources of national identity. The first discussions of bushido at this time were not the work of conservative reactionaries, however, but were conceived by relatively progressive individuals with considerable international experience and a command of Western languages. Some of the first modern writings on bushido clearly posit the concept as a potential native equivalent to the English ethic of “gentlemanship,” which was widely admired in late-nineteenth century Japan, and much of early bushido discourse should be seen primarily as a response to outside stimuli. This study examines the causes and effects of the “bushido boom” that took place between 1898 and 1914, which firmly established the concept not only in Japan, but throughout the world. In this context, this study analyzes the use of bushido by the Japanese military and educational system, as well as its popularization by prominent figures in the early twentieth century. This study also examines the reasons for the decline in the popularity of bushido between 1914 and the early 1930s, thereby providing points of departure for future research on the trajectory of bushido from 1932 to the present day.