Chapter I
Introduction

The available facts about the power of the atomic bomb as a military weapon lie in the story of what it did at Hiroshima and Nagasaki. Many of these facts have been published, in official and unofficial form, but mingled with distortions or errors. The United States Strategic Bombing Survey, therefore, in partial fulfillment of the mission for which it was established, has put together in these pages a fairly full account of just what the atomic bombs did at Hiroshima and Nagasaki. Together with an explanation of how the bomb achieved these effects, this report states the extent and nature of the damage, the casualties, and the political repercussions from the two attacks. The basis is the observation, measurement, and analysis of the Survey's investigators. The conjecture that is necessary for understanding of complex phenomena and for applying the findings to the problems of defense of the United States is clearly labelled.

When the atomic bombs fell, the United States Strategic Bombing Survey was completing a study of the effects of strategic bombing on Germany's ability and will to resist. A similar study of the effects of strategic bombing on Japan was being planned. The news of the dropping of the atomic bomb gave a new urgency to this project, for a study of the air war against Japan clearly involved new weapons and new possibilities of concentration of attack that might qualify or even change the conclusions and recommendations of the Survey as to the effectiveness of air power. The directors of the Survey, therefore, decided to examine exhaustively the effects of the atomic bombs, in order that the full impact on Japan and the implications of their results could be confidently analyzed. Teams of experts were selected to study the scenes of the bombings from the special points of emphasis of physical damage, civilian defense, morale, casualties, community life, utilities and transportation, various industries, and the general economic and political repercussions. In all, more than 110 men--engineers, architects, fire experts, economists, doctors, photographers, draftsman--participated in the field study at each city, over a period of 10 weeks from October to December, 1945. Their detailed studies are now being published.

In addition, close liaison was maintained with other investigating units. Cooperation was received from, and extended to, the following groups:

The Joint Commission for the Investigation of the Atomic Bomb in Japan.
The British Mission to Japan.
The Naval Technical Mission to Japan.

Special acknowledgment is due to the medical groups of the Joint Commission, whose data and findings have been generously made available to the Survey. On medical aspects of the bombings, the Joint Commission was the chief fact-finding group; it will present its definitive report in the near future. In other fields, however--particularly the study of physical damage and the impact on community life--the Survey collected its own data and is the primary source.

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