On August 6 1945, President Truman, when told that the atom bomb dropped on Hiroshima had been even more “conspicuous” than the test bomb in New Mexico, announced to Captain Frank Graham, “This is the greatest thing in history”. In June of that year Henry Stimson, US Secretary of State for War and a key adviser on the use of this new weapon, recorded an exchange with Truman:  “I was a little fearful that before we could get ready the Air Force might have Japan so thoroughly bombed out that the new weapon would not have a fair background to show its strength”, at which the president “laughed and said he understood.” At Potsdam, in July 1945, Winston Churchill and Clement Attlee had both acceded to Truman’s decision to use the Bomb. Around 80,000 died instantly at Hiroshima, with additional tens of thousands dying of radiation.