Hiroshima Nagasaki: The Real Story of the Atomic Bombings and Their Aftermathby Paul HamThomas Dunne Books/St. Martin's, 2014 Chemist Henry Linschitz, after witnessing the test-detonation of a nuclear bomb on 16 July 1945 in the New Mexico desert, asked: "My God, we're going to drop that on a city?"His horrified incredulity is easy to imagine. The bomb detonated at the "Trinity" test site briefly simulated the light and heat found on the surface of Earth's sun. In one instant, it released as much destructive energy as 20,000 tons of TNT (conventional explosives still being the only workable measuring standard, however paltry). Even in the most generous projection, Linschitz immediately saw, the detonation of such a device over a crowded city would result in apocalyptic levels of destruction.The Trinity test is conventionally regarded as the beginning of the Atomic Age, and it's the story of that fractious beginning - as much as of its two most famous missteps - that forms the subject of Paul Ham's utterly absorbing new book Hiroshima Nagasaki. He gives his readers the deep background not only of the atomic bomb's hurried and clandestine development at the height of the Second World War but also vivid portraits of the personalities involved in that development, including the famous roster of chemists and physicists like Einstein, Teller, Szilard, and Oppenheimer. At over 600 pages, this book dwarfs John Hersey's 1946 Hiroshima, but it very nearly equals that earlier book in its emotional power, and in its much greater historical sweep it can best be compared with the works of Richard Rhodes.At the heart of this familiar story is a familiar controversy: President Truman's decision to use this terrifying new weapon in war. In April of 1945, 183,000 American troops had assaulted the Japanese island of Okinawa and quickly ran up some stark statistics, including 12,500 killed, before Japanese resistance was broken. "The fall of Okinawa," Ham writes,

... sent a powerful message to Washington: an American land invasion of Japan proper would encounter far worse. The likely casualties weighed heavily on Truman, and his private misgivings about the invasion of the Japanese mainland which General MacArthur was planning and expected to lead deepened. Indeed, the President was loath to authorise the land invasion, given the human and political cost, and cast around for alternatives.

In Ham's account, the alternative of using atomic bombs despite overtures of peace being made by and extended to the Japanese rulership, was championed decisively by the new US Secretary of State, James Byrnes, who was sworn in on 3 July 1945 and "acted in some ways as a de facto president ... In coming weeks, Truman sat back to watch Byrnes tear apart these dovish tendencies." And in such an account, needless to say, the deep reservations of the scientists themselves were contemptuously disregarded, especially the kinds of suggestions embodied in documents like the Franck Report, in which those scientists urged the internationally-monitored detonation of a bomb on some deserted atoll, where its destructive power could be demonstrated without loss of life:

"The military advantages and the saving of American lives achieved by the sudden use of atomic bombs against Japan may be outweighed by the ensuing loss of confidence and by a wave of horror and revulsion sweeping over the rest of the world ... a demonstration of the new weapon might best be made before the eyes of representatives of all the United Nations, on the desert or a barren island." [Franck's emphasis]

Ham has Byrnes snarling and stomping his feet through all of this, angrily impatient with compromise, insisting that Japan's National Mobilisation Law (our author describes the result as "a ramshackle amalgam of dad's armies, women's brigades and youth fighters: weekend warriors and weekday indentured labour") would lead to a defense of the home islands so bloody and defiant it would make Okinawa look like a dress parade. Hundreds of thousands or even millions of US casualties were projected, and Byrnes was convinced a desert-island demonstration wouldn't sway the entrenched Japanese leadership - so Truman gave the orders.The center of Ham's book is of course those two catastrophic detonations. His account of Hiroshima's destruction has all the now-requisite unbelievable numbers:

The weapon exploded directly above Shima Hospital, in the centre of Hiroshima, instantly killing all patients, doctors and nurses. The heatwave charred every living thing within a 500-metre radius, and scorched uncovered skin at 2 kilometres. Those who saw the flash within this circle did not live to experience their blindness. The ground temperature ranged briefly from 3000 to 4000 degrees Celsius; iron melts at 1535 degrees Celsius. Water in tanks and ponds boiled. Leaves in distant parks turned crinkly brown, then to ash; tree trunks exploded. Tiles melted within 1100 metres - kilns achieve that effect at 1650 degrees Celsius.

When the response from a stunned Japanese government wasn't fast enough, another bomb was dropped on Nagasaki, and the Empire surrendered, and the war was over. The final segments of Ham's book deal swiftly with the many contested aftermaths of that neat solution, including Truman's own increasingly disoriented defenses of the thing he had done, and these segments are very, very good - the strongest part of the book. Ham also walks us through the various heartbreaking hypotheticals that have been raised around this subject since 1945 - including the one most likely to have become fact if given the chance:

What might have happened had America not used the atomic bombs? One probable scenario is this: within weeks Russia would have crushed Manchuria, and Japan - crippled by the naval blockade, subjected to constant conventional aerial attack, and fearful of the communist advance - would have surrendered to the more acceptable enemy, America. no US invasion would have been necessary. The total casualties, Allied and Japanese, of this scenario are unknowable.

Unknowable, Ham has the art to suggest but not say, being preferable to unthinkable.