The British military historian John Keegan observed that “historians are committed to controversy as a way of life.” It would be hard to find a better example of the essence of the historians’ craft – their “way of life” – than the controversy over the use of the atomic bomb. There may never be a definitive histories written of such a controversial event as the use of the bomb on Hiroshima and Nagasaki. Nevertheless, as our study shows, the Hiroshima controversy advanced historical knowledge through disagreement and debate. From the clash of ideas and controversy, from argument without end, historians draw closer to truth. For historians, “truth [like north] is a direction not a destination.” Realizing that multiple interpretations and controversy among historians are inevitable, historians formed professional associations where their ideas and interpretations could be debated and tested. In a time when authoritarians seek to control the writing of history, free societies need historians to preserve the freedom of their profession as a model of integrity in the pursuit of truth.