The Facts of the A-bombing

The population of Hiroshima City then is said around 350,000 including about 40,000 military-related people, but there is also another estimation. The 6th House Demolition Order, that had been implemented in July, 1945, had brought about 10,000 people of Volunteer corps from the surrounding towns and villages as well as mobilized students to the City. Adding more, who had been in the City for business, to them, the daytime population of Hiroshima was as many as 400,000. Of those, about 140,000 including 20,000 soldiers died by the end of December that year. (from the “Petition to the UN”, 1976) This figure tells us that about one out of the three in Hiroshima died for the following 5 months after the A-bombing. And those who survived the bombing had to suffer tremendously for years to come: physically, because of the aftereffects, mentally and financially because they lost their family, property and everything.


HIROSHIMA SPEAKS OUT The facts of the A-bombingA watch stopped at 8:15
Contributed by Kazuo Futakawa, exposed to the A-bomb 1.6km from the hypocenter

On August 6, 1945, at 8:15 in the morning an atomic bomb was dropped for the first time in human history. The B-29, Enola Gay, targeting at the T-shaped Aioi Bridge which was located in the middle of the city, released the bomb 31,600 feet (9,600meters) above the ground.

The atomic bomb, which is equivalent to 20 kilotons of TNT explosive power, exploded in the air 580 meters above Shima Hospital. Due to the intense flash and roaring sound at that moment, many A-bomb survivors later came to express the A-bombing as “pika-don”, meaning flash and boom. The moment the bomb blasted, a fireball 100 meters in diameter was formed and disappeared in 10 seconds.

Mushroom Cloud

Five minutes after the explosion, a gigantic cloud, about 3 miles (5 kilometers) in diameter, hung over the city of Hiroshima. Almost all the survivors say in their testimonies, “It became pitch dark and nothing could be seen”. That cloud was the reason. From the center of the cloud a pillar of white smoke rose, and reached to an altitude of 35,000 feet (17,000 meters). Then it spread out at the top, forming a shape of mushroom. So, people call it “mushroom cloud”.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
The mushroom cloud, about an hour after the explosion, shot by US Army from the Seto Inland Sea, 80 km in distance

The Power of the Atomic Bomb

It is said that 35% of the atomic bomb energy is thermal rays, 50%, blast wind and 15%, radiant heat rays.

1. Heat Rays

The atomic bomb exploded in the air 580 meters above the city. Right after the blast, a fireball was formed, and its immediate temperature reached approximately 1,000,000 degrees Celsius. The fireball swelled rapidly and disappeared in 10 seconds. Around the ground zero, it is estimated that heat rays of 6,000 degrees Celsius irradiated. One survivor who witnessed this fireball from a little distance expressed what he saw as follows, “I wondered if the sun fell on the city of Hiroshima”. The extremely high temperature of the bomb’s heat rays, comparable to the surface temperature of the sun, caused enormous damage on all the living things within 3 kilometers radius.

About 90 to 100 percent of people who were outside the building within 1 kilometer radius of the hypocenter died. The number of the instant deaths is not known. Near the ground zero, there was a case in which somebody melted or evaporated, leaving nothing but the shadow behind. Because of the instant flash of the heat rays, everything but the shadow was wiped out in the abnormal heat, so, it looked as if the shadow was printed on the road. Of those within 2 kilometers radius who were outside and had nothing to screen them, 83% of them died within a week.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
The shadow of the rail of the Yorozu bridge, 890 meters from the hypocenter, Photo taken by US Army

As for structures, wooden buildings within 3 kilometers are considered to have ignited automatically due to the heat rays before the blast wind of explosion. The fires raged like a “storm” and spread all over the city by the late afternoon. During the following three days the fires continued to smolder everywhere in the city.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
A man burned over his entire body; exposed within 1 km of the hypocenter,Photo by Masami Onuka (August 7, 1945)

2. Blast Wind

The fireball that was formed at the explosion of the atomic bomb created super high pressure, hundreds of thousands of atmospheric pressure. The gap between the abnormal high pressure and the atmospheric pressure caused blast wind. That blast wind was strong enough to destroy completely even concrete buildings within 800meters radius that were not earthquake-proof structures. In Hiroshima in those days most of the houses were wooden made, and within 2 kilometers radius all the wooden structures were destroyed.

Damages on the various structures caused by the blast wind.
(from Outline of the Counter measure Programs against the A-bomb victims)

distance from the hypocenter(m)maximum velocitydegree of damage
within 800m200-330m/secondentirely destroyed except earthquake proof structures
1,800m and less72-200m/secondall,badly destroyed
2,600m and less36-72m/secondwooden houses,no good at all for use
3,200m and less28-36m/secondpartly broken,usable if repaired

The damages caused by the blast wind and heat rays can be hard to distinguish clearly. These two and the fires that followed combined and interrelated in complexity, which contributed to the gigantic scale of devastation. All the structures except earthquake-proof concrete buildings within 2 kilometers radius from the hypocenter were entirely destroyed and burnt out. Even within 3 kilometers, more than 90% of the structures were broken and burnt down.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
City of Hiroshima soon after the A-bombing, Photo taken by US Army in October, 1945


When we talk about the damage by the atomic bombing, we never can miss “radiation”, a substance that had not been used before in human history, and should never have. In a Hiroshima-type of bomb, the percentage of its destructive power may be just 15%, but the terror initiated right after the A-bombing never disappears generations to come. Simply because some of its substances take tens of thousands of years even to halve its radioactivity. Also, it transforms the crimson of those who are exposed to it.

1. Acute A-bomb Disease

The physical disturbances caused by radiation, that were seen from the immediate after the A-bombing to around the end of that year, is called acute A-bomb disease. Within two weeks starting right after the bombing, nausea, diarrhea, high fever, general malaise, etc. were observed, which were followed by hair epilation, hemorrhage from the gum, purple spots and so on. Those who did not have any visible injuries by the A-bombing and looked well died one after another.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
Soldier who was exposed to the bomb about 1km from the hypocenter, and showing the acute symptoms such as hair loss, bleeding from the gum and purple spots by hypodermic bleeding. He died shortly after. Photo taken by Kenichi Kimura in the end of August, 1945 (from Hiroshima Peace Site)

2. After effects

The damage by the A-bomb in clear distinction from that of other weapons is, perhaps, that nobody knows when and what sort of disturbances will occur. The major aftereffects known so far are A-bomb cataract, leukemia and malignant tumor. As for genetic effects, nothing clear is confirmed to this day and continuous observation is needed for generations to come.

Occurrence of the A-bomb aftereffects

keloidOne year later
LeukemiaFive year later
Thyroid gland cancer10 years later
Breast cancer,Lung cancer20 years later
Stomach cancer,Colon cancer,Marrow cancer30 years later

3. Black rain

The monstrous black cloud after the explosion moved north-north west from the central part of the city for 20 to 30 minutes. From 9 o’clock in the morning to about 4 o’clock in the afternoon it brought rain showers in the areas, north and west of Hiroshima. The first one or two hours, the raindrops were muddy, sticky and pitch-black. Because they contained muddy dirt that had been whirled up at the explosion as well as soot from the fires that followed the blast. Also contained in the rain were radioactive substances, therefore those who were directly caught by this “black rain” had to suffer later the same symptoms as those who were directly exposed to the A-bombing.

Rescue Operations

At the time the atomic bomb exploded, those people near the hypocenter were instantly killed. Immediately after the explosion the fires were started and spread. Many people who were trapped under the buildings collapsed by the blast failed to escape and were burned alive. People, who narrowly survived though suffering from bad burns, ran all around to find safe refuges to lay themselves. Their dresses were tattered and torn. They were almost naked. Their skin was burned and hanging. Losing the energy to speak and walk, they were just staggering and tottering in a long line. As many eyewitnesses said, it was“just like a parade of the ghosts”.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
Badly burned victims fleeing from a sea of fire in the city. Around 8:45 on August 6, 1945 About 2.200 meters from the hypocenter. Drawn by Terumasa Hirata

On the other hand, there were people who went into the burning city to seek for their families and relatives. They searched around day after day, being often blocked by the flames of the fires. Army Marine Regiment Headquarters (commonly known as the Akatsuki Corps), which was located 4 kilometers away from the hypocenter, was damaged only slightly. The corps immediately went into the central part of the city and started the rescue operations, using ships and trucks.

Besides, many people came into the city from the nearby towns and villages, being told that a serious thing had happened in the city of Hiroshima. These people who were involved in the rescue activities were exposed to the residual radiation. Later they were found to be suffering from the A-bomb distance. They are called entry survivors. People were not told that the bomb dropped on Hiroshima was the atomic bomb.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
Injured people lying on the straw mats in the classroom at school About 3.100 meters from the hypocenter. Shot by Army Marine Regiment Headquarters

Heavily injured victims, who were carried out of the city, were sent to Ninoshima Island where there was Army Quarantine Station, or other first aid stations which were set up at more than 50 places in the city. However there were very few doctors and nurses in the city because it had been severely destroyed. Soon all the medicines were used up. There were no other ways to treat the victims except for changing the bandages, or applying oil or mercurochrome. It was the hottest time in summer, so the injuries easily suppurated and were infested with maggots, which annoyed the victims. The charred bodies were collected and cremated here and there in the city. These operations continued day in and day out.

HIROSHIMA SPEAKS OUT The facts of the A-bombing
Cremating the bodies collected by trucks, at the riverbank August 17, 1945 About 2.000 meters from the hypocenter, Drawn by Shigeo Fuji

Reference Literature

  • “War damage history of Hiroshima A-bombing, Volume 1 Comprehensive Account” August 6, 1971 published by Hiroshima City Office
  • “Outline of the Assistance Measures for the A-bomb Victims” July, 1998 published by the Hiroshima City Social Affairs Bureau, A-bomb Victims Assistance Measures Section
  • “A-bomb Radiation Effects on Human Bodies, Precis 1992” March 31, 1993, the first copy, compiled by International Medical Cooperation Promoting Council for the Radiation Victims. Published by Bunkodo Co.
  • “The Spirit of Hiroshima” 1999, the first copy, published by the Hiroshima Peace Memorial Museum
  • “Hiroshima Peace Reader” July 20, 1978, the first edition, published by the Hiroshima Peace Culture Foundation. Written by Yoshiteru Kosakai

Photos and Pictures provided by

  • Hiroshima Peace Memorial Museum
  • Hiroshima Council for Counter-measures against Atomic-bomb distance
  • Yoshito Matsushige
  • Talking Hiroshima with Youth of Today

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