During the Twentieth century, Reinhold Niebuhr was not only an important public intellectual but also a seminal thinker in IR. His prophetic voice echoed in the American culture from the Thirties until the Sixties and beyond. At the same time, statesmen and public opinion found in his political theory an essential contribute both for reflection and action. However, the protestant theologian suffered a harsh contrast by scholars, in particular by the positivist ones. This article analyses the path of Niebuhr’s international political thought across the “Great Debates” of IR. From the First “mythical” debate until the last and still open one, it examines the role of Niebuhr’s Christian realism in the development of the discipline. By using Flannery O’Connor’s concept of “realist of distances”, this essay tries to prove how Niebuhr was able to anticipate and, what’s more, exceed all debates.