The effects of atomic bomb on Hiroshima Nagasaki
THE ATTACKS AND DAMAGE
1. The attacks.--
A single atomic bomb, the first weapon of its type ever used against a target, exploded over the city of Hiroshima at 0815 on the morning of 6 August 1945. Most of the industrial workers had already reported to work, but many workers were enroute and nearly all the school children and some industrial employees were at work in the open on the program of building removal to provide firebreaks and disperse valuables to the country. The attack came 45 minutes after the "all clear" had been sounded from a previous alert. Because of the lack of warning and the populace's indifference to small groups of planes, the explosion came as an almost complete surprise, and the people had not taken shelter. Many were caught in the open, and most of the rest in flimsily constructed homes or commercial establishments.The bomb exploded slightly northwest of the center of the city. Because of this accuracy and the flat terrain and circular shape of the city, Hiroshima was uniformly and extensively devastated. Practically the entire densely or moderately built-up portion of the city was leveled by blast and swept by fire. A "fire-storm," a phenomenon which has occurred infrequently in other conflagrations, developed in Hiroshima: fires springing up almost simultaneously over the wide flat area around the center of the city drew in air from all directions. The inrush of air easily overcame the natural ground wind, which had a velocity of only about 5 miles per hour. The "fire-wind" attained a maximum velocity of 30 to 40 miles per hour 2 to 3 hours after the explosion. The "fire-wind" and the symmetry of the built-up center of the city gave a roughly circular shape to the 4.4 square miles which were almost completely burned out.
The surprise, the collapse of many buildings, and the conflagration contributed to an unprecedented casualty rate. Seventy to eighty thousand people were killed, or missing and presumed dead, and an equal number were injured. The magnitude of casualties is set in relief by a comparison with the Tokyo fire raid of 9-10 March 1945, in which, though nearly 16 square miles were destroyed, the number killed was no larger, and fewer people were injured.
At Nagasaki, 3 days later, the city was scarcely more prepared, though vague references to the Hiroshima disaster had appeared in the newspaper of 8 August. From the Nagasaki Prefectural Report on the bombing, something of the shock of the explosion can be inferred:
The day was clear with not very much wind--an ordinary midsummer's day. The strain of continuous air attack on the city's population and the severity of the summer had vitiated enthusiastic air raid precautions. Previously, a general alert had been sounded at 0748, with a raid alert at 0750; this was canceled at 0830, and the alertness of the people was dissipated by a great feeling of relief.
The city remained on the warning alert, but when two B-29's were again sighted coming in the raid signal was not given immediately; the bomb was dropped at 1102 and the raid signal was given a few minutes later, at 1109. Thus only about 400 people were in the city's tunnel shelters, which were adequate for about 30 percent of the population.
When the atomic bomb exploded, an intense flash was observed first, as though a large amount of magnesium had been ignited, and the scene grew hazy with white smoke. At the same time at the center of the explosion, and a short while later in other areas, a tremendous roaring sound was heard and a crushing blast wave and intense heat were felt.
The people of Nagasaki, even those who lived on the outer edge of the blast, all felt as though they had sustained a direct hit, and the whole city suffered damage such as would have resulted from direct hits everywhere by ordinary bombs.
The zero area, where the damage was most severe, was almost completely wiped out and for a short while after the explosion no reports came out of that area. People who were in comparatively damaged areas reported their condition under the impression that they had received a direct hit. If such a great amount of damage could be wreaked by a near miss, then the power of the atomic bomb is unbelievably great.
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NAGASAKI . . . "like a graveyard with not a tombstone standing . . ."
Nagasaki Prefecture Report
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In Nagasaki, no fire storm arose, and the uneven terrain of the city confined the maximum intensity of damage to the valley over which the bomb exploded. The area of nearly complete devastation was thus much smaller; only about 1.8 square miles. Casualties were lower also; between 35,000 and 40,000 were killed, and about the same number injured. People in the tunnel shelters escaped injury, unless exposed in the entrance shaft.The difference in the totals of destruction to lives and property at the two cities suggests the importance of the special circumstances of layout and construction of the cities, which affect the results of the bombings and must be considered in evaluating the effectiveness of the atomic bombs. An account of the nature and history of each city will give meaning to the details of the damage and disorganization at each.
2. Hiroshima.--
The city of Hiroshima is located on the broad fan-shaped delta of the Ota River, whose 7 mouths divide the city into 6 islands which project fingerlike into Hiroshima Bay of the Inland Sea. These mouths of the river furnished excellent firebreaks in a city that is otherwise flat and only slightly above sea level. A highly developed bridge system, with 81 important bridges, joined the islands. A single kidney shaped hill in the eastern part of the city, about one-half mile long and rising to an elevation of 221 feet, offered some blast protection to structures on the eastern side opposite the point of fall of the bomb. Otherwise, the city was uniformly exposed to the spreading energy from the bomb.The city boundary extends to some low hills to the west and northeast and embraces 26.36 square miles, only 13 of which were built up. Seven square miles were densely or moderately built up, the remainder being occupied by sparsely built-up residential, storage, and transportation areas, vegetable farms, water courses, and wooded hilly sections. In the central area, no systematic separation of commercial, industrial, and residential zones existed, though there were rough functional sections. The main commercial district was located in the center of the city, and with the adjoining Chugoku Regional Army Headquarters occupied the greater portion of the central area. The bulk of the industries was located on the perimeter of the city, either on the southern ends of the islands (where the Hiroshima airport was also situated) or to the east of the city. The 4 square miles of densely built-up area in the heart of the city--residential, commercial, and military--contained three-fifths of the total population. If there were, as seems probable, about 245,000 people in the city at the time of the attack, the density in the congested area must have been about 35,000 per square mile. Five completed evacuation programs and a sixth then in progress had reduced the population from its wartime peak of 380,000.
In Hiroshima (and in Nagasaki also) the dwellings were of wood construction; about one-half were one story and the remainder either one and one-half or two stories. The roof coverings were mostly hard-burnt black tile. There were no masonry division walls, and large groups of dwellings clustered together. The type of construction, coupled with antiquated fire-fighting equipment and inadequately trained personnel, afforded even in peacetime a high possibility of conflagration. Many wood-framed industrial buildings were of poor construction by American standards. The principal points of weakness were the extremely small tenons, the inadequate tension joints, and the inadequate or poorly designed lateral bracings.
Reinforced concrete framed buildings showed a striking lack of uniformity in design and in quality of materials. Some of the construction details (reinforcing rod splices, for example) were often poor, and much of the concrete was definitely weak; thus some reinforced concrete buildings collapsed and suffered structural damage when within 2,000 feet of ground zero, and some internal wall paneling was demolished even up to 3,800 feet. (For convenience, the term "ground zero" will be used to designate the point on the ground directly beneath the point of detonation, or "air zero.")
Other buildings, however, were constructed far more strongly than is required by normal building codes in America, to resist earthquakes. Furthermore, construction regulations in Japan have specified since the 1923 earthquake that the roof must safely carry a minimum load of 70 pounds per square foot whereas American requirements do not normally exceed 40 pounds per square foot for similar types. Though the regulation was not always followed, this extra strong construction was encountered in some of the buildings near ground zero at Hiroshima, and undoubtedly accounts for their ability to withstand atomic bomb
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pressures without structural failures. Nearly 7 percent of the residential units had been torn down to make firebreaks.Hiroshima before the war was the seventh largest city in Japan, with a population of over 340,000, and was the principal administrative and commercial center of the southwestern part of the country. As the headquarters of the Second Army and of the Chugoku Regional Army, it was one of the most important military command stations in Japan, the site of one of the largest military supply depots, and the foremost military shipping point for both troops and supplies. Its shipping activities had virtually ceased by the time of the attack, however, because of sinkings and the mining of the Inland Sea. It had been relatively unimportant industrially before the war, ranking only twelfth, but during the war new plants were built that increased its significance. These factories were not concentrated, but spread over the outskirts of the city; this location, we shall see, accounts for the slight industrial damage.
The impact of the atomic bomb shattered the normal fabric of community life and disrupted the organizations for handling the disaster. In the 30 percent of the population killed and the additional 30 percent seriously injured were included corresponding proportions of the civic authorities and rescue groups. A mass flight from the city took place, as persons sought safety from the conflagration and a place for shelter and food. Within 24 hours, however, people were streaming back by the thousands in search of relatives and friends and to determine the extent of their property loss. Road blocks had to be set up along all routes leading into the city, to keep curious and unauthorized people out. The bulk of the dehoused population found refuge in the surrounding countryside; within the city the food supply was short and shelter virtually nonexistent.
On 7 August, the commander of the Second Army assumed general command of the counter measures, and all military units and facilities in the area were mobilized for relief purposes. Army buildings on the periphery of the city provided shelter and emergency hospital space, and dispersed Army supplies supplemented the slight amounts of food and clothing that had escaped destruction. The need far exceeded what could be made available. Surviving civilians assisted; although casualties in both groups had been heavy, 190 policemen and over 2,000 members of the Civilian Defense Corps reported for duty on 7 August.
The status of medical facilities and personnel dramatically illustrates the difficulties facing authorities. Of more than 200 doctors in Hiroshima before the attack, over 90 percent were casualties and only about 30 physicians were able to perform their normal duties a month after the raid. Out of 1,780 nurses, 1,654 were killed or injured. Through some stocks of supplies had been dispersed, many were destroyed.
Only three out of 45 civilian hospitals could be used, and two large Army hospitals were rendered unusable. Those within 3,000 feet of ground zero were totally destroyed, and the mortality rate of the occupants was practically 100 percent. Two large hospitals of reinforced concrete construction were located 4,900 feet from ground zero. The basic structures remained erect but there was such severe interior damage that neither was able to resume operation as a hospital for some time and the casualty rate was approximately 90 percent, due primarily to falling plaster, flying glass, and fire. Hospitals and clinics beyond 7,000 feet, though often remaining standing, were badly damaged and contained many casualties from flying glass or other missiles.
With such elimination of facilities and personnel, the lack of care and rescue activities at the time of the disaster is understandable; still, the eyewitness account of Father Siemes1 shows how this lack of first-aid contributed to the seriousness of casualties. At the improvised first-aid stations, he reports:
* * * Iodine is applied to the wounds but they are left uncleansed. Neither ointment nor other therapeutic agents are available. Those that have been brought in are laid on the floor and no one can give them any further care. What could one do when all means are lacking? Among the passerby, there are many who are uninjured. In a purposeless, insensate manner, distraught by the magnitude of the disaster, most of them rush by and none conceives the thought of organizing help on his own initiative. They are concerned only with the welfare of their own families--in the official aid stations and hospitals, a good third or half of those that had been brought in died. They lay about there almost without care, and a very high percentage succumbed. Everything was lacking, doctors, assistants, dressings, drugs, etc. * * *
Effective medical help had to be sent in from in the outside, and arrived only after a considerable delay.
Fire-fighting and rescue units were equally stripped of men and equipment. Father Siemens.
3. Nagasaki--
Nagasaki is located on the best natural harbor of western Kyushu, a spacious inlet in the mountainous coast. The city is a highly congested urban pattern extending for several miles along the narrow shores and up the valleys opening out from the harbor. Two rivers, divided by a mountain spur, form the two main valleys in whose basins the city lies: the Urakami River, in whose basin the atomic bomb fell, running into the harbor from a NNW direction, and the Nakashima River, running from the NE. This mountain spur and the irregular layout of the city effectively reduced the area of destruction.The main residential and commercial districts are intermingled in these two river basins. The large industrial plants stretch up the west shore of the bay and up the Urakami Valley. Though the metropolitan area of the city is officially about 35 square miles and stretches far into the countryside, the heavily built-up area is confined by the terrain to less than 4 square miles. The greatest population density thus approximated 65,000 per square mile even after the evacuations.
Despite its excellent harbor, Nagasaki's commercial importance, though great in previous centuries, had declined in recent years because of the city's isolated peninsular position and the difficulties of transportation through the mountains by inadequate roads and railroad facilities. As a naval base it had been supplanted by Sasebo. Industry gradually increased in importance, primarily under Mitsubishi influence. The four largest companies in the city were the Mitsubishi Shipyards, Electrical Equipment Works, Arms Plant, and Steel Works, employing nearly 90 percent of the city's labor force. Administratively, Nagasaki was by 1941 of merely local importance despite being the seat of the prefectural government.
Before the atomic bombing on 9 August, Nagasaki had experienced five small-scale air attacks in the previous 12 months, by an aggregate of 136 planes which dropped a total of 270 tons of high explosive, 53 tons of incendiary, and 20 tons of fragmentation bombs.
Of these, a raid of 1 August 1945 was most effective, with several bombs falling in the Mitsubishi Shipyards and Steel Works. The scale of effect can be roughly measured, however, by comparing the toll of building damage with that from the atomic bomb; in all these raids 276 residential buildings and 21 industrial buildings were destroyed or badly damaged. When the atomic bomb fell, Nagasaki was comparatively intact.
Because the most intense destruction was confined to the Urakami Valley, the impact of the bomb on the city as a whole was less shattering than at Hiroshima. In addition, no fire storm occurred; indeed, a shift in wind direction helped control the fires. Medical personnel and facilities were hard-hit, however. Over 80 percent of the city's hospital beds and the Medical College were located within 3,000 feet of the center of the explosion, and were completely destroyed. Reinforced concrete buildings within this range, though standing , were completely gutted by fire; buildings of wooden construction were destroyed by fire and blast. The mortality rate in this group of buildings was between 75 and 80 percent. Exact casualty figures for medical personnel are unknown, but the city seems to have fared better than Hiroshima: 120 doctors were at work on 1 November, about one-half of the preraid roster.
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GROUND ZERO AT NAGASAKI--Before and after bombing.
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Casualties were undoubtedly high: 600 out of 850 medical students at the Nagasaki Medical College were killed and most of the others injured; and of the 20 faculty members, 12 were killed and 4 others injured.Utilities and services were again disrupted. Both gas plants were destroyed, and the replacement time was estimated at several months. Though the basic water supply was not affected, thousands of residential feeder-line breaks were supplemented by eight breaks on a 14-inch main line and four breaks where another main line crossed a bridge. Electric power distribution and transmission systems were effectively destroyed in the area of heaviest destruction, but power could be supplied to the other parts of the city almost immediately.
Shipping was virtually unaffected. Trolley service was halted both by the interruption in power supply and by damage to street cars. Nagasaki is at the end of a railroad spur line. The major damage was sustained by track and railroad bridges. The rails buckled intermittently for a bridges. The rails buckled intermittently for a distance of 5,000 to 7,500 feet from ground zero, at points where burning debris set fire to wooden cross ties. Three bridges were displaced; rails were distorted and the tracks had to be completely rebuilt. The railroad stations were completely destroyed by blast and fire and the electric signal destroyed by blast and fire and the electric signal system was severely damaged. Rolling stock was slightly damaged, primarily by fire. Although the damage to equipment was not extensive, it was severe enough to curtail traffic for 48 hours, during which time sufficient emergency repair work was performed to permit resumption of limited traffic.
Control of relief measures was in the hands of the prefecture. The sequence of clearance and repair activities illustrates the activities that were carried on. The city's repair facilities were completely disorganized by the atomic bomb, so that with the single exception of shutting off water to the affected areas no repairs were made to roads, bridges, water mains, or transportation installations by city forces. The prefecture took full responsibility for such restoration as was accomplished, delegating to the scattered city help the task of assisting in relief of victims.
There were only 3 survivors of 115 employees of the street car company, and late as the middle of November 1945 no cars were running. A week after the explosion, the water works officials made an effort to supply water to persons attempting to live in the bombed-out areas, but the leakage was so great that the effort was abandoned. It fell to the prefecture, therefore, to institute recovery measures even in those streets normally the responsibility of the city. Of the entire public works construction group covering the Nagasaki city area, only three members appeared for work and a week was required to locate and notify other survivors.
On the morning of 10 August, police rescue units and workers from the Kawaminami shipbuilding works began the imperative task of clearing the Omura-Nagasaki pike, which was impassable for 8,000 feet. A path 6 1/2 feet wide was cleared despite the intense heat from smoldering fires, and by 15 August had been widened to permit two-way traffic. No trucks, only rakes and shovels, were available for clearing the streets, which were filled with tile, bricks, stone, corrugated iron, machinery, plaster, and stucco. Street areas affected by blast and not by fire were littered with wood.
Throughout the devastated area, all wounded had to be carried by stretcher, since no motor vehicles were able to proceed through the cluttered streets for several days. The plan for debris removal required clearance of a few streets leading to the main highway; but there were frequent delays caused by the heat of smoldering fires and by calls for relief work. The debris was simply raked and shoveled off the streets. By 20 August the job was considered complete. The streets were not materially damaged by the bomb nor were the surface or the abutments of the concrete bridges, but many of the wooden bridges were totally or partially destroyed by fire.
Under the circumstances--fire, flight of entire families, destruction of official records, mass cremation--identification of dead and the accurate count of casualties was impossible. As at Hiroshima, the season of the year made rapid disposal of bodies imperative, and mass cremation and mass burial were resorted to in the days immediately after the attack. Despite the absence of sanitary measures, no epidemics broke out here. The dysentery rate rose from 25 per 100,000 to 125 per 100,000. A census taken on 1 November 1945 found a population of 142,700 in the city.
At Nagasaki, the scale of destruction was greater than at Hiroshima, though the actual area destroyed was smaller because of the terrain and the point of fall of the bomb. The Nagasaki Prefectural Report describes vividly the impress of the bomb on the city and its inhabitants:
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RESIDENTIAL AREAS, NAGASAKI. Shielded by hills, one congested area survived (note firebreak in the foreground).
Another, 1,000 feet northeast of ground zero was reduced to rubble.
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