In the early twentieth century, Korean Catholic and Protestant Churches found themselves in a period of significant power transition, from a neo-Confucian dynasty to a colonial regime. Imperial Japan and Christianity thus posed a mutual challenge: church leaders worked to sustain and increase their Evangelical mission field within Korea's new socio-political environment, while, simultaneously, the Japanese depended on the cooperation of the Korean Christian communities to fulfil their colonial project. In this dynamic of State-Church relations, Catholics and Protestants constantly vied for ascendancy. This article examines how the two Christian denominations engaged with each other and with Korea's coloniser, as imperial Japan's policies varied and its international status fluctuated.