 Hiroshima. August 6, 1945. For any real appreciation of the destruction involved here, we must have some idea of what originally existed as the target. If Hiroshima, as it existed before the bomb exploded, were to have been located in the United States, it would have been slightly smaller than Miami or San Diego, but larger than Dayton. It would have contained about as many people as Wyoming. With its population of 245,000, Hiroshima was the 7th largest city in Japan. Hiroshima was built on flat terrain except for a single low hill in the eastern part of the city. The fan-shaped delta of the Ota River provided natural fire breaks, sufficient to prevent the spread of fire of any normal incendiary attack. In addition, 7% of the city's residential units had been torn down to make supplementary fire breaks. Residential units in general were of wooden construction, like these in Kyoto. About half being one story and the remainder one and a half to two stories high. Scattered throughout the city were a few brick wall-bearing buildings, similar to those found in America. Of the reinforced concrete buildings, some were of poor construction by American standards. Others were earthquake resistant and stronger than most similar multi-story American buildings. Structural steel was chiefly reserved for industrial plants. The main commercial district of Hiroshima was located in the center of the city, with residential areas and military barracks overlapping and surrounding it. The bulk of the large industries were located on the perimeter. The far edges of the city were sparsely populated and consisted of vegetable farms, wooded hills, storage and transportation areas. These sections were beyond the effective limit of the bomb. Four square miles in the center of the city contained three fourths of the total inhabitants. Here the population density per square mile was slightly greater than Brooklyn, New York. Living conditions in Hiroshima were comparable to these seen in Kyoto. There were numerous one-to-five-man workshops in the commercial and residential districts. These provided a fourth of the city's total industrial production. However, the bulk of Hiroshima's output came from large plants like these, which were located in the outskirts of the city. Transportation and communications were well developed. Waterworks and sewage disposal plants were modern. Power and light facilities were up to date. Hospitals were well equipped. There was an adequate police force and a trained fire department with fairly modern equipment. These then were the elements, which characterized Hiroshima on the morning of August 6, 1945. It is important to keep them in mind in order to effectively appraise what came after. This is what happened. The bomb exploded in the air some distance above this point on the ground, which we shall call Ground Zero. The extent of material damage can be illustrated by superimposing the same area over Washington, D.C., where we can well imagine the effect of a similar bomb on the normal political, military, and economic functions of the capital. The atomic explosion achieved its results at Hiroshima by the release of energy in three forms, blast, heat, and radiation. Blast, as from a high-explosive bomb, caused severe damage over the entire area within a radius of one and a half miles of Ground Zero. Radiation, as from X-rays or radium, ultimately caused the death of almost everyone who was fully exposed up to half a mile from Ground Zero. Heat, liberated in one blinding flash by the explosion, caused flash burns and may have ignited isolated fires as far as a mile from Zero. Blistering of roof tile occurred up to 4,000 feet, but the majority of initial fires in buildings originated from secondary sources, such as short circuits, and kitchen charcoal fires when buildings were collapsed by blast. These hundreds of fires burning simultaneously resulted in a firestorm, a combined heat of the multiple conflagrations eventually drawing air into the vortex at a velocity of 30 to 40 miles an hour. The firestorm almost completely burned out the four and a half square mile center of the city, an area which had already been severely damaged by blast. In this area, 50 buildings of reinforced concrete remained standing. All of these suffered some degree of blast damage, and all except a dozen were gutted by the fires which spread from surrounding wood buildings. Severe blast damage to one-story light steel frame buildings was extensive over an area of three and a half square miles, the damage extending on an average of slightly over a mile from Ground Zero. Multi-story brick buildings were seriously damaged over approximately the same area. Wood domestic buildings were wrecked within a six square mile area, up to one and a half miles from Ground Zero. One-story brick buildings with load-bearing walls were wrecked over a similar area. Damage to machinery depended upon the construction of the buildings in which it was housed. In wood frame buildings, 95% of the equipment was rendered unusable, mostly by fire and debris. On the other hand, in reinforced concrete buildings, only 25 to 30% was seriously affected. Debris was a major cause of destruction only in those reinforced concrete buildings where walls and roofs collapsed. Of the machines housed in steel frame industrial buildings, about 5% suffered damage primarily caused by the movement of structures, which crushed or overturned adjacent equipment. The subsequent exposure to the weather was what rendered most of the remaining equipment unserviceable. In all 62,000 buildings in the urban area were destroyed and 6,000 severely damaged. Street pavements were not directly affected by the bomb, but the thoroughfares themselves were unnegotiable because of enormous amounts of debris. Steel and concrete bridges, although damaged, remained usable. Wooden bridges were destroyed by fire. Transportation facilities were almost completely paralyzed. Automobiles, buses and bus terminals were extensively damaged by blast and fire. Street cars were burned out, but railroad rolling stock losses were generally light because of their location at the perimeter of the bomb's range. Through service was resumed two days after the attack. Communications such as the telephone system were 80% knocked out. Service was not restored for 10 days. The water reservoir two miles from the blast center, made of reinforced concrete and earth covered, was undamaged. However, 70,000 pipe connection breaks in buildings and dwellings resulted from blast and fire. No subsurface pipes were crushed and no leaks in these pipes were caused directly by blast, though several underground failures resulted from falling debris. Pressure in the city dropped to zero because of the connection breaks and the damaged domains where they crossed damaged bridges. Six sewer pumping stations were rendered inoperable by fire and blast. The electric power transmission and distribution system in the center of the city was wrecked. Only power equipment of rugged construction, such as transformers, resisted blast and heat within the devastated areas. Instruments were demolished beyond repair. Switches, switchyard insulators, cables and copper bus work were ruined. And yet electric power from the general network was available in most of the surviving parts of the city within 24 hours. The gas supply failed as a result of severe damage to gas holders up to one and a quarter miles from ground zero. Medical facilities were virtually wiped out. All but three of the 45 civilian hospitals were at least temporarily neutralized. The casualty rate of occupants of hospitals within 3,000 feet of ground zero was practically 100%. In many cases, basic structures remained intact, but falling plaster, fire and flying glass caused the casualties. 90% of the 200 doctors in the city were killed or injured. 1,600 out of 1,700 nurses were killed or injured. Firefighting and rescue units like these were stripped of personnel and equipment. It is unlikely that any municipal fire department in the world could have prevented the firestorm at Hiroshima. The immediate effect of the annihilation of Hiroshima among the survivors was uncontrolled terror accompanied by hysterical activity or flight from the city for shelter and food. Within a few days, however, people had started their return and the task of reconstruction began. Each family had to do what it could as there was no organized plan for rehabilitation. At Nagasaki, the destructive capacity of the bomb used was greater than that at Hiroshima, but the actual area raised was smaller because of the terrain and the point of fall of the bomb. The area completely devastated was less than two square miles compared to Hiroshima's four and a half square miles. Multi-story reinforced concrete buildings, however, were structurally damaged over a wider area than at Hiroshima. This was partly because of the greater power of the bomb and partly because buildings of this type, mostly schools and hospitals, were not as strongly constructed as comparable office and commercial buildings at Hiroshima. Destruction to factories was greater at Nagasaki because of the city's position as an armament center and because of the location of these plants nearer the blast center. Steel frame industrial buildings were stripped of their sheet metal cover. The frames were generally pushed over en masse by the force of the blast. The three Mitsubishi firms together with the dockyards were responsible for 90% of the industrial output of the city. They were all hard hit. The steel works would have required a year to get back into substantial production. The electric works on the other hand could have resumed production at a reduced rate within two months. It could have reached capacity within six. The arms plants would have required 15 months to reach two-thirds of their former capacity. Transportation too suffered heavily. There were only three survivors out of 115 employees of the streetcar company. Even after two months, there were no cars running. The railroad was also severely crippled. Wood ties were fired up to 7,000 feet. Rails buckled and bridges were damaged. Stations were completely destroyed. The electric power transmission and distribution systems were wrecked. Gas holders were knocked out. Medical facilities fared badly. The medical college and 80% of the city's hospital beds were located within 3,000 feet of ground zero. They were almost completely destroyed. Casualties for the city as a whole, however, stood at 50% less than at Hiroshima. While the conflagration with its uniformly burnt out area was the most evident characteristic at Hiroshima, at Nagasaki, the blast effects with their resemblance to the aftermath of a hurricane were most striking. This is illustrated by the remains of this Catholic cathedral located a third of a mile from ground zero. The difference in the totals of destruction to lives and property between the two cities suggests the importance of the special circumstances of their layout and construction. These differences had a direct bearing on the results of the bombings and must be considered in evaluating the effectiveness of atomic demolition. Had Nagasaki been flat and had it been completely built up with no water, wooded areas, or intervening hills, the damage area would have been considerably greater than at Hiroshima. We have seen what took place at Hiroshima and Nagasaki. What happened to homes and factories, to schools and hospitals, to transportation and communications, to public services of all kinds, to the people themselves. From these scenes we have some measure of the magnitude of the disaster which would befall an American city under an atomic bomb attack.