Wide ranging, deeply researched, and clearly expressed, Preston’s history of the influence of religion on U.S. foreign policy, from Colonial times through the Obama administration, is a landmark in the field of American foreign policy studies. Religion has influenced U.S. foreign policy in many ways: the personal convictions of U.S. presidents and other leaders, the political power of religious organizations, and the public voices of religious thinkers and leaders, such as Reinhold Niebuhr and Billy Graham, have all had an impact on U.S. policy choices. Preston links the theological convictions of men such as Abraham Lincoln, William McKinley, the two Roosevelts, Harry Truman, and Dwight Eisenhower to the policy choices they made. His analysis demonstrates that religious influence has hardly been limited to the political right: liberal and even radical approaches to foreign policy have also reflected religious ideas and lobbying. As in any work of this scope, it is impossible for Preston to get everything right or address every issue. But his book sets a standard for investigations into this subject that future scholars will struggle to match.