Biography, specifically royal biography, was a key ideological component of Japan’s justification for the annexation of the Ryukyu Kingdom in 1879 and its conversion into Okinawa Prefecture. In his capacity as a former U.S. president, Ulysses S. Grant mediated the dispute between Meiji Japan and Qing China that subsequently ensued. The Meiji government based the legitimacy of its annexation on irredentism, specifically, the assertions that the Ryukyuan people were closely related to the Japanese people, and that Ryukyuan kings were related to Japanese emperors. While historical and linguistic evidence were critical to the former, biography was critical for the latter, and Grant found Japan’s irredentist claims compelling enough for him to support the Meiji government’s claims over Okinawa, much to the dismay of Qing officials.