The global wars and totalitarian regimes of the first half of the twentieth century led many Protestants to believe that the world's only hope for lasting peace rested in a new world order grounded in Christian ethics. This dissertation examines international campaigns for ecumenism and racial integration during that time and reveals how the Japanese American incarceration changed religious and racial boundaries within mainline American Protestantism. Several months after the attack on Pearl Harbor, President Roosevelt allowed the incarceration of nearly 120,000 people of Japanese descent. People struggled with the reality that the United States was fighting a war against ideologies of racial supremacy within fascist regimes while imprisoning American citizens on the basis of their race. If American Protestants could not maintain a just social structure at home, they could not hope to do so globally. Subsequent reflections on the church's religious and racial structures fostered two unprecedented experiments: church authorities required ecumenical worship within the camps and interracial worship among Japanese and European Americans after the war. In this way, the incarceration ironically created an opportunity to move toward goals of religious and racial unity--steps to a new world order. However, attempts to enforce ecumenical and interracial worship exposed historical tensions among denominations and challenged preconceptions about the viability and desirability of united worship. The mixed results of these experiments--primarily failures--gradually led mainline Protestants to expand their definition of unity to include pluralist representations of Christianity as imagined by different sects and ethnic groups. As Japanese Americans realized the value of their ethnic congregations, theologians formed the first manifestations of Asian American theology. Broadly, this project explores how religious people and institutions responded to injustice and global strife during this era. The perspectives and responses of Japanese pastors and congregants, camp administrators and the leaders of national and regional Protestant organizations collude to create a comprehensive view of the situation. Using oral histories, textual sources and visual artifacts, this dissertation contends with race and ethnicity, global ecumenism, the formation of Asian American theology, regional dynamics in the US and the role of religion during war.