God's Marshall Plan deepens our understanding of the crucial role religious actors, ideas, and aid played in the international relations between the United States and Germany from the Progressive Era to the Cold War. From the early twentieth century onward, American Protestant religious leaders and policymakers worked hand-in-hand to advance an international agenda of "democratization" and "Christianization." Their efforts to establish "World Christianity"—a godly global order that was both Christian and democratic—and activate "Christian America" culminated in "God's Marshall Plan," a theopolitical intervention in Germany that sought to reshape the defeated nation's religious and civic culture. Seeing vibrant religious life as essential to a functioning democracy, these Americans worked to export American religious values such as lay activism, voluntarism, stewardship, and ecumenism to Germany. Through launching a far-reaching relief program that made humanitarianism a central pillar within Protestant internationalism, they also helped forge a Christian and democratic coalition between West Germany and the United States. As such, the Protestant ecumenical movement became a vehicle for American national interests in post-war Germany and the expansion of America's "empire by invitation" in Western Europe. "God's Marshall Plan" furthermore marked a turning point in the twentieth century relationship between German and American Protestantism. As theological actors, ideas, and relief flowed across the Atlantic, American Protestants worked to remake German-American relations through positioning themselves as the leaders of global Protestantism. On their side of the Atlantic, Germans both welcomed American aid while also contesting the Americanization of their religious life. "God's Marshall Plan" thus marked a flash point in a shared German-American Protestant culture that is much more vibrant and contentious than historians have recognized. Although the German Protestant church maintained much of its conservative character immediately after the war, the grassroots adoption of American theologies promoted reform and transformation. By the end of the Adenauer era in 1963, German Protestantism had emerged as an ecumenical and activist force in in its own right. Protestant activism increasingly targeted, however, American foreign policies in the Cold War. As Germans contested nuclear proliferation and the Vietnam War, the coalition around Christian and democratic values that had turned one-time enemies into close allies began to fracture and come to an end.