The case for realism in US foreign policy is often associated today with arguments for offshore detachment and non-intervention—along with a certain impatience regarding ethical or religious considerations. The great classical realists of the 1940s possessed views on international relations much richer and more varied than this. The political thought of Christian theologian Reinhold Niebuhr is an excellent example of that richness. Described by the realist George Kennan as “the father of us all,” Niebuhr could hardly ignore moral considerations in foreign policy. Nor was he against unmasking moralistic or delusional pretensions on international matters. Far from it. Yet Niebuhr’s consistent recognition of the limits of American power and self-awareness did not lead him to advocate either appeasement or disengagement. Rather, beginning in 1940, he made the case for a sober, realistic, and morally grounded US involvement overseas, out of the central admission that whatever America’s own faults, a punctilious detachment from world affairs might very well result in the triumph of greater imbalances and injustices. This was Niebuhr’s Christian realism.

It was the issue of creeping US involvement in the war against Nazi Germany throughout 1940–41 that catalyzed, defined, and popularized Reinhold Niebuhr’s approach to international relations. Originally a pacifist himself, Niebuhr had always possessed doubts as to whether the main strength of the pacifist stance was in its moral validity per se, or simply in the post-World War I feelings of sheer nausea regarding violence—particularly in a country comfortable with the status quo. By 1934, he abandoned his dedication to absolute non-resistance for the same reason that he abandoned much of his earlier liberal idealism; he no longer viewed pacifism as a universally viable strategy in the struggle against injustice. While this position was originally reached on domestic matters—in defense of labor’s right to strike—the implications for foreign policy would be drawn out in the face of expanding tyranny and disorder overseas. Worried by Japanese expansion in China, appalled by the mistreatment of Jews in Hitler’s Reich, and sensitive to the shift in power represented by the 1938 Munich agreement, Niebuhr came to be a leading advocate for US entry into World War II. With books, articles, sermons, lectures, and public hearings, he argued for aid to the United Kingdom, for convoys, for Lend-Lease, for repeal of the Neutrality Acts, and for economic sanctions against Japan. In 1940–41, he launched a new journal, Christianity and Crisis; wrote the book Christianity and Power Politics; helped found the Union for Democratic Action; and testified before the Senate Foreign Relations Committee, all in the hopes of mobilizing public opinion for intervention. Above all, he worked to convince mainstream liberal Protestants that they had not only a right but an obligation to aid Britain against Nazi Germany.

The debate over aid to the UK revealed a deep division within American Protestant churches between a liberal, pacifist, idealistic ethic on the one hand, and an Augustinian or Christian realist one on the other. Unlike many realists, Niebuhr never denied the validity of what he called a religious or “witness” pacifism, such as that practiced by Quakers or Mennonites. These conscientious objectors made no claim to easy solutions; instead, they reminded their contemporaries of the truth that every use of force, and every proximate political achievement, however well-intended, stood under a higher judgment. For many modern pacifists, however, non-resistance was a practical, political strategy that promised a relatively easy victory over conflict and injustice. In Niebuhr’s view, this “political” pacifism was a distortion of the Christian ethic, in that it failed—like liberalism—to recognize the tragic elements in social life: the persistence of power and self-interest, the imperfectability of human institutions, and above all the tenuous and reversible nature of moral and material progress. Pacifists insisted that war and violence were the greatest imaginable evils in communal life. But how would they secure relative justice in cases where peaceful methods had failed? In effect, their answer was to abdicate responsibility, and surrender to oppression and injustice, bowing out of their social obligations under the cover of a righteous superiority. As Niebuhr puts it:

No matter how they twist and turn, the protagonists of a political, rather than a religious, pacifism end with the acceptance of and justification of, and connivance with, tyranny. They proclaim that slavery is better than war. I beg leave to doubt it and to challenge the whole system of sentimentalized Christianity which prompts good men to arrive at this perverse conclusion.

For Niebuhr, the pacifism prevalent in America’s mainstream liberal Protestant churches represented a myopic, moralistic, and utopian version of Christianity—a new “Pelagian heresy” with potentially devastating consequences. By seeking to stay out of war at any cost, pacifists unwittingly aided Nazi Germany, and condoned “a tyranny which has destroyed freedom, is seeking to extinguish the Christian religion, debases its own subjects to robots who have no opinion and judgment of their own, threatens the Jews of Europe with complete annihilation and all the nations of Europe with subordination under a ‘master race.’” The mistake such pacifists made was to think they could live in history without sin or guilt; but in truth, no such possibility existed. Our duty in social conflict, Niebuhr suggested, was not a fastidious non-participation, but a conscientious choice of what might necessarily be the lesser evil. As he puts it, “Whatever may be wrong with the British Empire… it is still obvious that these nations preserve certain values of civilization, and that the terror which is sweeping over Europe is not civilization. A moralism which dulls the conscience against this kind of evil is perverse.” A lofty sense of compassion, a horror of war, needed to be complemented and bolstered by the intermediary social virtue of justice. And justice sometimes required the use of force to balance competing interests and prevent abuses of power, whether abroad or at home.

By 1940–41, then, as he gave his Gifford lectures at Edinburgh to the sound of Luftwaffe bombing raids, Niebuhr had arrived at a Christian realist political perspective—a perspective he would maintain, in its essentials, for the rest of his life. After a number of twists and turns, his ideological journey from a jejune liberal idealism to a more grounded political realism was largely complete. Reflecting on the disorders of his age, and drawing on a wide range of Christian thinkers—Søren Kierkegaard, Blaise Pascal, John Calvin, Martin Luther, and above all St. Augustine—Niebuhr had joined the ranks of “neo-orthodox” theologians determined to throw a classical biblical understanding of sin and transcendence back in the face of modern pretensions. The events of his time, it seemed, had refuted all utopian illusions, whether liberal or Marxist, secular or religious, based as they were upon a commonly over-optimistic faith in human nature and political progress. The heated debate over pacifism and intervention had given his thoughts on international relations, in particular, their mature and developed form. It remained to reconstruct a more realistic Christian political ethic, from the ground up, with such a reorientation. US foreign policy could then be guided through the twin rocks of naïve idealism on the one hand, and self-defeating cynicism on the other.