On August 6 and 9, 1945, the 503rd Composite Group of the Army Air Forces dropped a single bomb on each of two Japanese cities, Hiroshima and Nagasaki. The cities were devastated, with tens of thousands killed in the blast, the subsequent firestorm, and the days of starvation and chaos that followed, not to mention the many more who suffered from lingering effects in the years to come. As is universally known today – but was not always understood then – these were atomic (more precisely, nuclear or fission) bombs, which generated their tremendous power from the splitting of the heavy atomic nuclei of uranium (Hiroshima’s Little Boy) or plutonium (Nagasaki’s Fat Man). They have never been used in combat since, yet from this first catastrophic revelation to global humanity they have been integral to the relationship of the United States with the world.