My current project, tentatively entitled “Enemies of the Cross” to “Brethren in Faith”: Global Politics and the End of Europe’s Protestant-Catholic War, 1885-1965, explores the intersections of European religious culture and international politics. In particular, it investigates the surprising end of Europe’s Catholic-Protestant conflict. For centuries, European Christian religious, political, and cultural life had been divided along denominational lines; and anti-Catohlicism and anti-Protestantism were powerful cultural tropes. During the late 1950s and early 1960s, however, Europe experienced a radical revolution in intra-Christian relations. After centuries of mutual hostility, Catholics and Protestants across the continent increasingly began making peace with each other; they founded common social associations, cooperated in lay organizations, and declared they were “brethren in faith.” While scholars have largely attributed this unanticipated shift to the trauma of Nazi persecution or the Cold War, this project argues that another major motor behind it was the collapse of Europe’s colonial project. For centuries, both Catholic and Protestant organizations had been active participants in European imperial expansion. Much of the hostility between them therefore stemmed from a sense of global competition: the belief that only they truly represented the West’s “civilizing mission.” Yet the challenges of postwar decolonization changed their calculations. A growing sense that European—and Christian—expansion was ending and that Europe’s cultural and religious influence was on the decline led Protestants and Catholics to view each other as necessary partners in the fight against Islam, Communism, and nationalist revolutionary ideologies in Africa, Asia, and the Pacific. This cooperation in turn laid the groundwork for their shifting views in Europe. Drawing on multiple sources and archives, this project uncovers the relationships between dramatic intellectual and international transformations.