Andrew Rotter does not usually write about nuclear weapons. The Colgate University Charles A. Dana Professor of History is known for his works on twentieth-century American diplomatic history. He was approached, ‘out of the blue’, by David Reynolds in the summer of 2001, just before the attack on the Twin Towers. Reynolds, well known for his writings on the so-called ‘special relationship’ between the two English-speaking powers on either side of the Atlantic, was advising Oxford University Press on its series of the significant events of the twentieth century. Few events were more significant than the use of a nuclear weapon on Hiroshima in August 1945.