During World War II, teams of scientists raced to build the ultimate weapon: the atomic bomb. This weapon, everyone believed, was so powerful that it would force the Japanese to surrender immediately, eliminating the need for an extremely costly invasion of the Japanese main islands. They built two weapons using two different models: Little Boy, a uranium gun-style weapon, and, just in case the first one wasn’t enough, the Fat Man, a plutonium implosion weapon. When the weapons were ready, President Truman, who knew nothing about the Manhattan Project until Roosevelt’s death, struggled mightily with the moral implications of using these ultimate weapons. The atomic bomb, once dropped on Hiroshima, and then three days later, on Nagasaki, proved America’s overwhelming military superiority to the Japanese, and they promptly surrendered.

If you attended an American high school, this roughly outlines the story you learned about the end of World War II. Perhaps you had an in-class debate about the morality of dropping the bomb. You may have also learned that the decision to drop the bomb was influenced by a desire to impress Stalin, as the the wartime alliance was beginning to fray.

Michael Gordin’s Five Days in August challenges the central premise of this story: that the atomic bomb was perceived as a weapon qualitatively different from what we now call conventional weaponry. Instead, he argues, many (though not all) of the scientists and political and military decision makers understood the new nuclear weapons as simply a more powerful and efficient method of delivering destruction than conventional weaponry, and that this viewpoint was dominant. Although the atomic bomb was part of a larger plan to “shock and awe” the Japanese into surrender, it was only one component of that plan, along with the conventional firebombing of Japanese cities and the entry of the Soviet Union into the war in the Pacific. Most people involved expected the war to continue for some time longer–at the very least, into September, and they expected that they would need to continue to deliver additional atomic weapons throughout this period. The true impact of the atomic bomb, particularly its radiological effects, was unknown, even to the Manhattan Project scientists, who initially discounted reports of radiation sickness in Hiroshima and Nagasaki as Japanese propaganda. The US was surprised not only by the effects of the atomic bombs, but also by the speed of the Japanese surrender.

Gordin makes a convincing case that when World War II became the first (and hopefully last) nuclear war, the people in charge did not fully grasp that they had ushered in a new era. The idea that nuclear weapons are the “unusable weapon” was not immediately obvious, as war-planners not only used the weapons, but planned to use them repeatedly, as fast as they could produce them.

I do wish that he had spent more time on this transformation, though. The final chapter, which discusses the post-war world, doesn’t really explain how the atomic bomb changed from “really efficient deliverer of destruction” to “weapon of the apocalypse”; he notes briefly that the popular imagination was moved by the propaganda about the new weapon’s power and journalistic accounts of the destruction at Hiroshima and Nagasaki, but we don’t get much insight into the transformation from either the popular perspective or the policy/military perspective. Perhaps that will be fodder for a future project.