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Weapons of Mass Destruction (WMD)

Hiroshima - 06 August 1945

At 2:45 a.m. on 06 August 1945, the Allies' B-29 "Enola Gay" left the island of Tinian near Saipan. Its primary target was Hiroshima, where the 2nd Japanese Army stood poised to defend against an expected Allied invasion of their homeland. The Enola Gay was carrying "Little Boy," a 9,700-pound uranium bomb. Piloted by the commander of the 509th Composite Group, Colonel Paul Tibbets, the B-29 flew at low altitude on automatic pilot before climbing to 31,000 feet as it neared the target area. The weather over the target was satisfactory, and the bombardier, Major Thomas Ferrebee, was able to use a visual approach.

August 6th began with a bright, clear, summer morning. About 7 AM, there was an air raid alarm which had become an almost daily event, and a few planes appeared over the city (the weather plane). No one paid attention, and at about 8:00 AM the all-clear sounded. At approximately 8:15 AM Hiroshima time the Enola Gay released Little Boy over the city. Tibbets immediately dove away to avoid the anticipated shock wave. Forty-three seconds later, a huge explosion lit the morning sky as Little Boy detonated directly over a parade field where soldiers of the Japanese Second Army were doing calisthenics. The bomb's detonation point was only approximately 550 feet from the aiming point, the Aioi Bridge, an easily identifiable location near the center of the city. The bomb detonated at an altitude of 1800 feet. The yield of the bomb was 12.5 KT (kilotons, the equivalent of 12,500 tons of TNT).

Though already eleven and a half miles away, the Enola Gay was rocked by the blast. At first, Tibbets thought he was taking flak. After a second shock wave (reflected from the ground) hit the plane, the crew looked back at Hiroshima. "The city was hidden by that awful cloud . . . boiling up, mushrooming, terrible and incredibly tall," Tibbets recalled.

On the ground moments before the blast it was a calm and sunny Monday morning. By 8:15 the city was alive with activity -- soldiers doing their morning calisthenics, commuters on foot or on bicycles, groups of women and children working outside to clear firebreaks. Those closest to the explosion died instantly, their bodies turned to black char. Nearby birds burst into flames in mid-air, and dry, combustible materials such as paper instantly ignited as far away as 6,400 feet from ground zero.

Pika Don

Those who survived called the A-bomb "pika don". "Pika" referred to the flash of light, and "Don" was an onomatopoeic reference to the tremendous sound. Survivors close to the hypocenter, the point directly beneath the detonation, heard no sound, and called it meerely "pika".

The detonation formed a high-temperature, high-pressure fireball which rapidely expanded to a diameter of about 400 meters in the first second. The fireball emitted intense heat for three seconds, and glowed brightly for about ten seconds. The temperature on the ground near the hypocenter reached thousands of degrees Celsius. On the ground near the hypocenter the overpressure reached tons per square meter. The fireball created a supersonic shockwave, which was followed by winds blowing hundreds of meters per second. The shock wave traveled eleven kilometers in 30 seconds.

The white light acted as a giant flashbulb, burning the dark patterns of clothing onto skin (right) and the shadows of bodies onto walls. Survivors outdoors close to the blast generally describe a literally blinding light combined with a sudden and overwhelming wave of heat. (The effects of radiation are usually not immediately apparent.) The blast wave followed almost instantly for those close-in, often knocking them from their feet.

Those that were indoors were usually spared the flash burns, but flying glass from broken windows filled most rooms, and all but the very strongest structures collapsed. One boy was blown through the windows of his house and across the street as the house collapsed behind him. Within minutes 9 out of 10 people half a mile or less from ground zero were dead.

People farther from the point of detonation experienced first the flash and heat, followed seconds later by a deafening boom and the blast wave. Nearly every structure within one mile of ground zero was destroyed, and almost every building within three miles was damaged.

In the case of wooden houses, those which were within one kilometer of the hypocenter were smashed at the moment of the explopsion. In the case of reinforced concrete buildings, the roofs of those near the center of the explosion collapsed. Some of the buildings were flattened and became piles of rubble. A fierce fire followed destruction by the violent blast caused by the explosion. Every building within one kilometer of the hypocenter was totally destroyed by the fire whether it was wooden or reinforced concrete.

Wooden houses in the area between one kilometer and two kilometers from the hypocenter were completely destroyed. The buildings located one to two kilometers from the center were mostly destroyed by the fire. Wooden houses in the area two to three kilometers away were severely damaged. Even houses three to four kilometers from the center of the explosion were badly damaged. The buildings two to three kilometers from the center were partially destroyed.

Less than 10 percent of the buildings in the city survived without any damage, and the blast wave shattered glass in suburbs twelve miles away. The most common first reaction of those that were indoors even miles from ground zero was that their building had just suffered a direct hit by a bomb.

The firestorm eventually engulfed 4.4 square miles of the city, killing anyone who had not escaped in the first minutes after the attack. One postwar study of the victims of Hiroshima found that less than 4.5 percent of survivors suffered leg fractures. Such injuries were not uncommon; it was just that most who could not walk were engulfed by the firestorm.

The Day After

The A-bomb destroyed all levels of administration, transportation facilities, including railroads, the communication system, journalism, offices, factories of private and public corporations, and all other facilities. The total destruction of these facilities caused such great confusion that it was utterly impossible to grasp the number of dead and wounded.

On the evening of August 6, Vice Inspector General Hattori of the Chugoku District Superintendent's Office, Director of Hiroshima Prefectural Police Ishihara, and Governor Genshin Takano, who had returned from a business trip, gathered at Tamon-in Temple at the entrance to Hijiyama Park. They formed both a temporary prefectural government office and a temporary air-defence headquarters. Thirteen hours later they reported the disastrous situation and asked for help from the central government and other related organizations. Therefore relief activities on the day of the explosion were almost limited to the Akatsuki Corps sent from Ujina, naval personnel sent from the naval base at Kure, and a few small hospitals which survived the disaster.

Small ad hoc rescue parties soon began to operate, but roughly half of the city's population was dead or injured. In those areas most seriously affected virtually no one escaped serious injury. The numerous small fires that erupted simultaneously all around the city soon merged into one large firestorm, creating extremely strong winds that blew towards the center of the fire.

Even after the flames had subsided, relief from the outside was slow in coming. For hours after the attack the Japanese government did not even know for sure what had happened. Radio and telegraph communications with Hiroshima had suddenly ended at 8:16 a.m., and vague reports of some sort of large explosion had begun to filter in, but the Japanese high command knew that no large-scale air raid had taken place over the city and that there were no large stores of explosives there.

Eventually a Japanese staff officer was dispatched by plane to survey the city from overhead, and while he was still nearly 100 miles away from the city he began to report on a huge cloud of smoke that hung over it. The first confirmation of exactly what had happened came only sixteen hours later with the announcement of the bombing by the United States. Relief workers from outside the city eventually began to arrive and the situation stabilized somewhat. Power in undamaged areas of the city was even restored on August 7th, with limited rail service resuming the following day.

Several days after the blast, however, medical staff began to recognize the first symptoms of radiation sickness among the survivors. Soon the death rate actually began to climb again as patients who had appeared to be recovering began suffering from this strange new illness. Deaths from radiation sickness did not peak until three to four weeks after the attacks and did not taper off until seven to eight weeks after the attack. Long-range health dangers associated with radiation exposure, such as an increased danger of cancer, would linger for the rest of the victims' lives, as would the psychological effects of the attack.

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Page last modified: 24-07-2011 04:33:30 ZULU