THE ATOMIC BOMBINGS OF HIROSHIMA AND NAGASAKI

by The Manhattan Engineer District, June 29, 1946.

Index

FOREWORD INTRODUCTION THE MANHATTAN PROJECT INVESTIGATING GROUP PROPAGANDA SUMMARY OF DAMAGES AND INJURIES MAIN CONCLUSIONS THE SELECTION OF THE TARGET DESCRIPTION OF THE CITIES BEFORE THE BOMBINGS Hiroshima Nagasaki THE ATTACKS Hiroshima Nagasaki GENERAL COMPARISON OF HIROSHIMA AND NAGASAKI GENERAL DESCRIPTION OF DAMAGE CAUSED BY THE ATOMIC EXPLOSIONS TOTAL CASUALTIES THE NATURE OF AN ATOMIC EXPLOSION CHARACTERISTICS OF THE DAMAGE CAUSED BY THE ATOMIC BOMBS CALCULATIONS OF THE PEAK PRESSURE OF THE BLAST WAVE LONG RANGE BLAST DAMAGE GROUND SHOCK SHIELDING, OR SCREENING, FROM THE BLAST FLASH BURN CHARACTERISTICS OF INJURIES TO PERSONS BURNS MECHANICAL INJURIES BLAST INJURIES RADIATION INJURIES SHIELDING FROM RADIATION EFFECTS OF THE ATOMIC BOMBINGS ON THE INHABITANTS OF THE CITIES APPENDIX: Father Siemes' eyewitness account

FOREWORD

This report describes the effects of the atomic bombs which were dropped on the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945, respectively. It summarizes all the authentic information that is available on damage to structures, injuries to personnel, morale effect, etc., which can be released at this time without prejudicing the security of the United States.

This report has been compiled by the Manhattan Engineer District of the United States Army under the direction of Major General Leslie R. Groves. Special acknowledgement to those whose work contributed largely to this report is made to:

The Special Manhattan Engineer District Investigating Group, The United States Strategic Bombing Survey, The British Mission to Japan, and

The Joint Atomic Bomb Investigating Group (Medical). and particularly to the following individuals:

Col. Stafford L. Warren, Medical Corps, United States Army, for his evaluation of medical data,

Capt. Henry L. Barnett, Medical Corps, United States Army, for his evaluation of medical data,

Dr. R. Serber, for his comments on flash burn,

Dr. Hans Bethe, Cornell University, for his information of the nature of atomic explosions,

Majors Noland Varley and Walter C. Youngs, Corps of Engineers, United States Army, for their evaluation of physical damage to structures,

J. 0. Hirschfelder, J. L. Magee, M. Hull, and S. T. Cohen, of the Los Alamos Laboratory, for their data on nuclear explosions,

Lieut. Col. David B. Parker, Corps of Engineers, United States Army, for editing this report.

INTRODUCTION

Statement by the President of the United States: "Sixteen hours ago an American airplane dropped one bomb on Hiroshima, Japan, and destroyed its usefulness to the enemy. That bomb had more power than 20,000 tons of T.N.T. It had more than two thousand times the blast power of the British Grand Slam, which is the largest bomb ever yet used in the history of warfare".

These fateful words of the President on August 6th, 1945, marked the first public announcement of the greatest scientific achievement in history. The atomic bomb, first tested in New Mexico on July 16, 1945, had just been used against a military target.

On August 6th, 1945, at 8:15 A.M., Japanese time, a B-29 heavy bomber flying at high altitude dropped the first atomic bomb on Hiroshima. More than 4 square miles of the city were instantly and completely devastated. 66,000 people were killed, and 69,000 injured.

On August 9th, three days later, at 11:02 A.M., another B-29 dropped the second bomb on the industrial section of the city of Nagasaki, totally destroying 1 1/2 square miles of the city, killing 39,000 persons, and injuring 25,000 more.

On August 10, the day after the atomic bombing of Nagasaki, the Japanese government requested that it be permitted to surrender under the terms of the Potsdam declaration of July 26th which it had previously ignored.