Question: When did Reinhold Niebuhr write "Moral Man and Immoral Society" and argue Christian Realism?
Context: Neorealism or structural realism is a theory of international relations that says power is the most important factor in international relations.  It was first outlined by Kenneth Waltz in his 1979 book "Theory of International Politics".  Alongside neoliberalism, neorealism is one of the most influential contemporary approaches to international relations; the two perspectives have dominated international relations theory for the last three decades.  Neorealism emerged from the North American discipline of political science, and reformulates the classical realist tradition of E.H. Carr, Hans Morgenthau, and Reinhold Niebuhr. Ethics (German: Ethik ) is an unfinished book by Dietrich Bonhoeffer that was edited and published after his death by Eberhard Bethge in 1949.  Bonhoeffer worked on the book in the early 1940s and intended it to be his "magnum opus".  At the time of writing, he was a double agent; he was working for Abwehr , Nazi Germany's military intelligence organization, but was simultaneously involved in the 20 July plot to assassinate Adolf Hitler.  The central theme of "Ethics" is Christlikeness.  The arguments in the book are informed by Lutheran Christology and are influenced by Bonhoeffer's participation in the German resistance to Nazism.  "Ethics" is commonly compared to Bonhoeffer's earlier book "The Cost of Discipleship", with scholars debating the extent to which Bonhoeffer's views on Christian ethics changed between his writing of the two books.  In "The Cambridge Companion to Dietrich Bonhoeffer", John W. de Gruchy argues that "Ethics" evinces more nuance than Bonhoeffer's earlier writings.  In 2012, David P. Gushee, director of Mercer University's Center for Theology and Public Life, named "Ethics" one of the five best books about patriotism, the others being Bruce Lincoln's "Religion, Empire and Torture"; Reinhold Niebuhr's "Moral Man and Immoral Society"; Shane Claiborne's and Chris Haw's "Jesus for President"; and "A Testament of Hope", a collection of Martin Luther King Jr.'s speeches and writings. Hans Joachim Morgenthau (February 17, 1904 – July 19, 1980) was one of the major twentieth-century figures in the study of international politics.  Morgenthau's works belong to the tradition of Realism in international-relations theory, and he is usually considered, along with George F. Kennan and Reinhold Niebuhr, one of the three leading American realists of the post-World War II period.  Morgenthau made landmark contributions to international relations theory and the study of international law.  His "Politics Among Nations", first published in 1948, went through five editions during his lifetime. Classical Realism is a theory of International Relations established in the post-World War II era that seeks to explain international politics as a result of human nature.  The theory is associated with thinkers such as Niccolò Machiavelli and Thomas Hobbes.  Modern thinkers associated with classical realism are Carl von Clausewitz, Hans Morgenthau and Reinhold Niebuhr.  Classical Realist thought has since been overshadowed by Neorealism after Kenneth Waltz' work became more widely accepted due to the rise of Structuralism in North American International Relations scholarship which favored the latter's emphasis on rationality rather than human nature as cause for political conflict. Moral Man and Immoral Society: A Study in Ethics and Politics is a 1932 book by Reinhold Niebuhr, an American Protestant theologian at Union Theological Seminary (UTS) in New York City.  The thesis of the book is that people are more likely to sin as members of groups than as individuals.  Niebuhr wrote the book in a single summer.  He drew the book's contents from his experiences as a pastor in Detroit, Michigan prior to his professorship at UTS.  The book attacks liberalism, both secular and religious, and is particularly critical of John Dewey and the Social Gospel.  "Moral Man and Immoral Society" generated much controversy and raised Niebuhr's public profile significantly.  Initial reception of the book by liberal Christian critics was negative, but its reputation soon improved as the rise of fascism throughout the 1930s was seen as having been predicted in the book.  Soon after the book's publication, Paul Lehmann gave a copy to Dietrich Bonhoeffer, who read it and was impressed by the book's thesis but disliked the book's critique of pacifism.  The book eventually gained significant readership among American Jews because, after a period of considerable anti-theological sentiment among Jews in the United States, many Jews began to return to the study of theology and, having no Jewish works of theology to read, turned to Protestant theological works. The Spirit of Democratic Capitalism is a 1982 book by philosopher Michael Novak, in which Novak aims to understand and analyze the theological assumptions of democratic capitalism, its spirit, it values, and its intentions.  Novak defines democratic capitalism as a pluralistic social system that contrasts with the unitary state of the traditional society and the modern socialist state.  He analyzes it as a differentiation of society into three power centers: a political sector, an economic sector, and a moral-cultural sector.  Each sector needs the others.  Democracy needs the market economy and both need a pluralistic liberal culture.  Against the continuing growth of democratic capitalism, modern socialism has contracted from a robust utopian program into vague “idealism about equality” and overwrought criticism of capitalism, most notably in the “liberation theology” of Latin America.  Novak ends with the “beginnings of a theological perspective on democratic capitalism” illuminated by the journey from Marxism to realism of Reinhold Niebuhr. The Niebuhr brothers were Reinhold Niebuhr and H. Richard Niebuhr, two American Christian scholars active in the first half of the 20th century. Helmut Richard Niebuhr (September 3, 1894 – July 5, 1962) is considered one of the most important Christian theological ethicists in 20th century America, most known for his 1951 book "Christ and Culture" and his posthumously published book "The Responsible Self".  The younger brother of theologian Reinhold Niebuhr, Richard Niebuhr taught for several decades at the Yale Divinity School.  Both brothers were, in their day, important figures in the neo-orthodox theological school within American Protestantism.  His theology (together with that of his colleague at Yale, Hans Wilhelm Frei) has been one of the main sources of postliberal theology, sometimes called the "Yale school".  He influenced such figures as James Gustafson, Stanley Hauerwas, and Gordon Kaufman. Christian Realism is a philosophical perspective developed by the theologian and public intellectual Reinhold Niebuhr in the late 1940s and early 1950s.  Niebuhr argued that the Kingdom of God cannot be realized on earth because of the innately corrupt tendencies of society.  Due to the injustices that arise on earth, a person is therefore forced to compromise the ideal of the kingdom of heaven on earth.  Niebuhr argued that human perfectibility was an illusion, highlighting the sinfulness of humanity at a time when the world was confronted by the horrors of experiences such World War II, the reigns of both Adolf Hitler and Joseph Stalin, and the Holocaust.  The movement was in part a reaction to the Social Gospel movement.  Numerous American political figures have been influenced by Christian realism, such as Martin Luther King Jr., Jimmy Carter, Barack Obama and Hillary Clinton. Karl Paul Reinhold Niebuhr ( ; June 21, 1892June 1, 1971) was an American theologian, ethicist, commentator on politics and public affairs, and professor at Union Theological Seminary for more than 30 years.  Niebuhr was one of America's leading public intellectuals for several decades of the 20th century and received the Presidential Medal of Freedom in 1964.  A public theologian, he wrote and spoke frequently about the intersection of religion, politics, and public policy, with his most influential books including "Moral Man and Immoral Society" and "The Nature and Destiny of Man", the second of which Modern Library ranked one of the top 20 nonfiction books of the twentieth century.  Andrew Bacevich labelled Niebuhr's book "The Irony of American History" "the most important book ever written on U.S. foreign policy."  Historian Arthur Schlesinger Jr. described Niebuhr as "the most influential American theologian of the 20th century" and "Time" posthumously called Niebuhr "the greatest Protestant theologian in America since Jonathan Edwards."
Answer: the twentieth century