This is the second episode in a three-episode series about "Oppenheimer" and the historical debates raised by the blockbuster film.

When Robert Oppenheimer accepted the job to lead the top-secret Manhattan Project, he and his fellow physicists expected any bomb would be used against Nazi Germany. But by the time the A-bomb was ready in late July 1945, Hitler was dead and Germany had surrendered. Some scientists questioned whether it was necessary to use "the gadget" against Japan, whose weakened military and industrial capacities could no longer project power across the Pacific. Christopher Nolan's cinematic masterpiece has revived interest in this contentious debate: could the Second World War had been won without destroying Hiroshima and Nagasaki? In this episode, eminent historian David M. Kennedy discusses the difficult circumstances of August 1945. For Americans who look back on it as "the good war," the destruction of Japan may raise uncomfortable moral and ethical questions.

Note: Audio excerpts of the "Oppenheimer" film are courtesy Universal Pictures. The source for Harry Truman's speeches is the Miller Center at the University of Virginia.