Money and finance have been among the most potent tools of colonial power. This study investigates the Japanese experiment with financial imperialism - or "yen diplomacy" - at several key moments between the acquisition of Taiwan in 1895 and the outbreak of the Sino-Japanese War in 1937. Through authoritarian monetary reforms and lending schemes, government officials and financial middlemen served as "money doctors" who steered capital and expertise to Japanese official and semi-official colonies in Taiwan, Korea, China, and Manchuria.