The lead-up to World War II (sometimes referred to as “the Fifteen-Year War”) dates back to the “Manchurian Incident” of 1931, but Japan's aggressive expansionist activities originated much earlier. Japan abandoned its centuries-old exclusionary policies with the arrival of Commodore Perry's “Black Ships” in 1853; other ambitious European powers soon followed. Inspired by the large-scale expansionism of the West during the late nineteenth century, Japanese imperialists realized as early as 1874 – when they gained control of the Rbl>yūkyūbl> Islands from China – that Japan could supplement its limited natural resources and fortify its defenses by gaining control of weaker Asian entities.

Military strength allowed for Japanese territorial expansion. In 1876, Japan forced Korea to concede special trading privileges; the Sino-Japanese War (1894–5) brought about the annexation of Formosa (Taiwan) and other valuable territories from China. The need to eliminate Russia as a competitor for power in Asia led to the Russo-Japanese War (1904–5). Japan's conclusive victory allowed it to acquire Guandong (Kwantung) Leased Territory and Karafuto (South Sakhalin). The way was thus cleared for the annexation of Korea in 1910, making Japan a major world power. In 1914, the Japanese Navy seized Nan'yo (Micronesia) from Germany under the terms of the South Pacific Mandate.

Japan's presence spurred the economic development of its new colonial territories, including railways, bridges, and other infrastructure that could bring Japan precious raw materials. However, it also imposed severely repressive colonialist controls, with Japanese military administrators keeping indigenous people in strict subjugation while the authorities, emulating Western colonial policies, existed in an elite Japan-centric society. Development of the colonized territories included both agricultural improvements and investment in heavy industry; education of both Japanese settlers and the local population was also a priority, with an emphasis on Japanese curricula, including teaching of the Japanese language.