This dissertation investigates the relationship between German Protestant missionaries and secular leaders of colonial politics and culture in the German colonial empire during the nineteenth century. In particular, it examines how missionaries defined their collective identity as an international one against pressures that encouraged mission societies to adopt and promote policies that favored the German colonial state and German colonial economic actors. Protestant missionaries in Germany created an alternative ideology to govern Germans' and Germany's relationships with the wider world. The dissertation examines the formation of an internationalist missionary methodology and ideology by German missionary intellectuals from 1870 and the shift to traditional Protestant nationalism during World War I. It then examines the application by missionaries of this ideology to the major issues of Protestant mission work in German East Africa: territorial rivalries with German Catholic mission orders, mission school policy, fundraising in the German metropole, and international missionary cooperation. In so doing, it revises conventional interpretations about the relationship between Protestantism and nationalism in Germany during this period.