From Knopf, an interesting new book by Cambridge historian Andrew Preston, Sword of the Spirit, Shield of the Faith: Religion in American War and Diplomacy (2012). Preston addresses a topic historians often neglect: the role of religion in American foreign policy. Americans are, by and large, a religious people, and this has influenced the way their government has acted on the world stage for centuries. Religion’s influence has been complex, inspiring progressive internationalists like Franklin Roosevelt (Prestons’s discussion of FDR’s religiosity was for me the most unexpected and intriguing part of the book) and conservative nationalists like George W. Bush. Nonetheless, Preston identifies a unifying theme, “Christian republicanism,” which he defines as “a blend of Protestant theology and democratic politics.” This worldview prizes religious liberty as the foundation of democracy and views it as the most important of human rights. Indeed, Preston shows how the protection of religious liberty abroad has been a constant theme in American diplomacy. In the nineteenth century, the State Department advocated for missionaries, including Mormons, with foreign governments, even though the Department often found the missionaries a nuisance. In the twentieth century, Henry Kissinger’s attempts to get Congress to grant the Soviet Union most-favored-nation status failed largely because Kissinger underestimated American sympathy for the plight of Soviet Jews. CLR Forum readers will be interested in the shifting perceptions of Catholicism. Although for much of American history, the Catholic Church was seen as adverse to Christian republicanism – McKinley famously justified the annexation of the Catholic Philippines in order to “Christianize” the Filipinos – that view changed during the Cold War, perhaps as a result of a common enemy America and the Church had in Communism. Preston closes his book with a prediction: although religion “may not always determine the direction” of American foreign policy, it “will be an ever-present factor.” That seems a good bet.