The devastation of World War I loomed in the background for Americans when war began in Europe in September 1939 and when the United States moved to assist Britain prior to entering the war in December 1941. Many members of the clergy realized in the wake of World War I that they had been duped by propaganda, and they recognized that the lofty principles over which the war was fought were never achieved. Making pledges to resist all wars, they cried, "never again," even when the shadow of Nazism fell over Europe. Religious groups resisted American entry into the war. That resistance set off a wide and intense debate about intervention. The Christian theologian Reinhold Niebuhr and his colleagues encouraged intervention, but they were the minority. Most mainline Christian groups opposed entry. Fundamentalists, meanwhile, looked to see if this would lead to the end...