Scholars have agreed that Japan's peripheral island of Okinawa has long been subjugated by both the U.S. and Japanese governments: despite long-standing opposition from the islanders, both governments have agreed to maintain U.S. military bases in Okinawa since they signed the Security Treaty Between the United States and Japan in 1951. My project aims to show that this U.S.-Japanese collaboration for imperial intervention into Okinawa in fact began in the late nineteenth century as American and Japanese Protestant missionaries worked closely to support Japan's colonization of Okinawa, which was originally an independent kingdom but forcefully incorporated into Japan in 1879. In illuminating the development of the U.S.-Japanese inter-imperial coalition, I explore how American and Japanese Protestant missionaries from various denominations expanded their own empires into the Ryukyu Kingdom/Okinawa from 1846 to 1919. I propose that while the Japanese missionaries took advantage of the financial and human resources of the American missionaries, the American missionaries, who regarded the Japanese were somewhat more "Westernized" than the "savage" Okinawans, could use the Japanese imperial network to further expand American cultural influence in Okinawa. The American and Japanese mission efforts culminated when, after the Okinawans' long opposition to Japan's colonization of their former kingdom, Okinawans who had converted to Christianity began to adopt a Japanese identity in the 1910s. I emphasize that in this process the Okinawan Christians were not passive recipients of imposed Japanese and American cultures but central historical actors, who attempted to overcome their second-class status in Japan by appealing to transnational Christian identity.