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Atomic Bombing of Hiroshima

the Atomic Bombing of Hiroshima

At 8:15 on the morning of August 6, 1945, the United States Army Air Forces dropped the nuclear weapon "Little Boy" on the city of Hiroshima, followed three days later by the detonation of the "Fat Man" bomb over Nagasaki, Japan. In his 1999 book Downfall, historian Richard Frank analyzed the many widely varying estimates of casualties caused by the bombings. He concluded "The best approximation is that the number is huge and falls between 100,000 and 200,000." Most of the casualties were civilians.

The role of the bombings in Japan's surrender, as well as the effects and justification of them, have been subject to much debate. In the U.S., the prevailing view is that the bombings ended the war months sooner than would otherwise have been the case, saving many lives that would have been lost on both sides if the planned invasion of Japan had taken place. In Japan, the general public tends to think that the bombings were needless as the preparation for the surrender was in progress in Tokyo.

Prelude to the bombings

The United States, with assistance from the United Kingdom and Canada, designed and built the bombs under the codename Manhattan Project; initially for use against Nazi Germany and inspired by the correct assumption that Germany would also conduct an atomic bomb project, and incorrect assumption that the Nazis held a lead in atomic weapons research. The first nuclear device, called "Gadget," was tested near Alamogordo, New Mexico on July 16, 1945. The Hiroshima and Nagasaki bombs were the second and third to be detonated and the only ones ever employed as weapons.

Hiroshima and Nagasaki weren't the first times that the Allies had bombed Axis cities without specifically targeting military installations, nor the first time that such bombings had caused huge numbers of civilian casualties, nor the first time that such bombings were (or came to be) controversial. In Germany, the Allied firebombing of Dresden resulted in roughly 30,000 deaths. The March 1945 firebombing of Tokyo may have killed as many as 100,000 people. By August, about 60 Japanese cities had been destroyed through a massive aerial campaign, including large firebombing raids on the cities of Tokyo and Kobe.

Over 3½ years of direct U.S. involvement in World War II, approximately 400,000 American lives had been lost, roughly half of them incurred in the war against Japan. In the months prior to the bombings, the Battle of Okinawa resulted in an estimated 50–150,000 civilian deaths, 100–125,000 Japanese or Okinawan military or conscript deaths and over 72,000 American casualties. An invasion of Japan was expected to result in casualties many times greater than in Okinawa.

U.S. President Harry S. Truman, who was unaware of the Manhattan Project until Franklin Roosevelt's death, made the decision to drop the bombs on Japan. His stated intention in ordering the bombings was to bring about a quick resolution of the war by inflicting destruction, and instilling fear of further destruction, that was sufficient to cause Japan to surrender. On July 26 Truman and other allied leaders issued The Potsdam Declaration outlining terms of surrender for Japan:

"...The might that now converges on Japan is immeasurably greater than that which, when applied to the resisting Nazis, necessarily laid waste to the lands, the industry and the method of life of the whole German people. The full application of our military power, backed by our resolve, will mean the inevitable and complete destruction of the Japanese armed forces and just as inevitably the utter devastation of the Japanese homeland..."

"...We call upon the government of Japan to proclaim now the unconditional surrender of all Japanese armed forces, and to provide proper and adequate assurances of their good faith in such action. The alternative for Japan is prompt and utter destruction."

The next day, Japanese papers reported that the declaration, the text of which had been broadcast and dropped on leaflets into Japan, had been rejected. The atomic bomb was still a highly guarded secret and not mentioned in the declaration.

Choice of targets

Secretary of War Henry L. Stimson struck Kyoto from the list because of its cultural significance, over the objections of Gen. Leslie Groves, head of the Manhattan Project. According to Professor Edwin O. Reischauer, Stimson "had known and admired Kyoto ever since his honeymoon there several decades earlier." On July 25 General Carl Spaatz was ordered to bomb one of the targets: Hiroshima, Kokura, Niigata or Nagasaki as soon after August 3 as weather permitted, and the remaining cities as additional weapons became available.


At the time of its bombing, Hiroshima was a city of considerable industrial and military significance. Even some military camps were located nearby, such as the headquarters of the Fifth Division and Field Marshal Shunroku Hata's 2nd General Army Headquarters, which commanded the defence of all of southern Japan. Hiroshima was a minor supply and logistics base for the Japanese military. The city was a communications centre, a storage point, and an assembly area for troops. It was one of several Japanese cities left deliberately untouched by American bombing, allowing an ideal environment to measure the damage caused by the atomic bomb. Another account stresses that after General Spaatz reported that Hiroshima was the only targeted city without POW-camps, Washington decided to assign it highest priority.

The centre of the city contained a number of reinforced concrete buildings and lighter structures. Outside the centre, the area was congested by a dense collection of small wooden workshops set among Japanese houses. A few larger industrial plants lay near the outskirts of the city. The houses were of wooden construction with tile roofs, and many of the industrial buildings also were of wood frame construction. The city as a whole was highly susceptible to fire damage.

The population of Hiroshima had reached a peak of over 381,000 earlier in the war, but prior to the atomic bombing the population had steadily decreased because of a systematic evacuation ordered by the Japanese government. At the time of the attack the population was approximately 255,000. This figure is based on the registered population used by the Japanese in computing ration quantities, and the estimates of additional workers and troops who were brought into the city may be inaccurate.

The bombing

A postwar "Little Boy" casing mockup

Hiroshima was the primary target of the first U.S. nuclear attack mission, on August 6, 1945. The B-29 Enola Gay, piloted and commanded by Colonel Paul Tibbets, was launched from Tinian airbase in the West Pacific, approximately 6 hours' flight time away from Japan. The drop date of the 6th was chosen because there had previously been a cloud formation over the target. At the time of launch, the weather was good, and the crew and equipment functioned properly. Navy Captain William Parsons armed the bomb during the flight, since it had been left unarmed to minimize the risks during takeoff. In every detail, the attack was carried out exactly as planned, and the gravity bomb, a gun-type fission weapon, with 60 kg (130 pounds) of uranium-235, performed precisely as expected.

About an hour before the bombing, the Japanese early warning radar net detected the approach of some American aircraft headed for the southern part of Japan. The alert had been given and radio broadcasting stopped in many cities, among them Hiroshima. The planes approached the coast at a very high altitude. At nearly 08:00, the radar operator in Hiroshima determined that the number of planes coming in was very small—probably not more than three—and the air raid alert was lifted. (To save gasoline, the Japanese had decided not to intercept small formations, which were assumed to be weather planes.) The three planes present were the Enola Gay (named after Colonel Tibbets' mother), The Great Artiste (a recording and surveying craft), and a then-nameless plane later called Necessary Evil (the photographing plane). The normal radio broadcast warning was given to the people that it might be advisable to go to air-raid shelters if B-29s were actually sighted, but no raid was expected beyond some sort of reconnaissance. At 08:15, the Enola Gay dropped the nuclear bomb called "Little Boy" over the centre of Hiroshima. It exploded about 600 meters (2,000 feet) above the city with a blast equivalent to 13 kilotons of TNT, killing an estimated 70–80,000 people. At least 11 U.S. POWs also died.[6] Infrastructure damage was estimated at 90% of Hiroshima's buildings being either damaged or completely destroyed.

Japanese realization of the bombing

The Tokyo control operator of the Japanese Broadcasting Corporation noticed that the Hiroshima station had gone off the air. He tried to re-establish his program by using another telephone line, but it too had failed. About twenty minutes later the Tokyo railroad telegraph centre realized that the main line telegraph had stopped working just north of Hiroshima. From some small railway stops within ten miles (16 km) of the city came unofficial and confused reports of a terrible explosion in Hiroshima. All these reports were transmitted to the Headquarters of the Japanese General Staff.

Military bases repeatedly tried to call the Army Control Station in Hiroshima. The complete silence from that city puzzled the men at Headquarters; they knew that no large enemy raid had occurred and that no sizeable store of explosives was in Hiroshima at that time. A young officer of the Japanese General Staff was instructed to fly immediately to Hiroshima, to land, survey the damage, and return to Tokyo with reliable information for the staff. It was generally felt at Headquarters that nothing serious had taken place, that it was all a terrible rumour starting from a few sparks of truth.

The staff officer went to the airport and took off for the southwest. After flying for about three hours, while still nearly 100 miles (160 km) from Hiroshima, he and his pilot saw a great cloud of smoke from the bomb. In the bright afternoon, the remains of Hiroshima were burning. Their plane soon reached the city, around which they circled in disbelief. A great scar on the land still burning, and covered by a heavy cloud of smoke, was all that was left. They landed south of the city, and the staff officer, after reporting to Tokyo, immediately began to organize relief measures.

The burns on this victim look like the kimono patterns; the lighter areas of the cloth reflected the intense light from the bomb, causing less damage

Tokyo's first knowledge of what had really caused the disaster came from the White House public announcement in Washington, sixteen hours after the nuclear attack on Hiroshima.

Radiation poisoning and/or necrosis caused illness and death after the bombing in about 1% of those who survived the initial explosion. By the end of 1945, thousands more people died due to radiation poisoning, bringing the total killed in Hiroshima in 1945 to about 90,000. Since then about a thousand more people have died of radiation-related causes. (According to the city of Hiroshima, as of August 6, 2005, the cumulative death toll among Hiroshima's atomic-bomb victims was 242,437. That figure includes everyone who was in the city when the bomb exploded, or was later exposed to fallout, who has since died.)

Survival of some structures

Some of the reinforced concrete buildings in Hiroshima were very strongly constructed because of the earthquake danger in Japan, and their framework did not collapse even though they were fairly close to the centre of damage in the city. As the bomb detonated in the air, the blast was more downward than sideways, which was largely responsible for the survival of the Prefectural Industrial Promotional Hall, now commonly known as the Genbaku, or A-bomb Dome designed and built by the Czech architect Jan Letzel, which was only a few meters from ground zero. (The ruin was named Hiroshima Peace Memorial and made a UNESCO World Heritage site in 1996 over the objections of the U.S. and China.)

Events of August 7-9

After the Hiroshima bombing, President Truman announced, "If they do not now accept our terms, they may expect a rain of ruin from the air the likes of which has never been seen on this earth." On August 8, 1945, leaflets were dropped and warnings were given to Japan by Radio Saipan. (The area of Nagasaki did not receive warning leaflets until August 10, though the leaflet campaign covering the whole country was over a month into its operations.) An English translation of that leaflet is available at PBS.

At one minute past midnight on August 9, Tokyo time, Russian infantry, armour, and air forces launched an invasion of Manchuria. Four hours later, word reached Tokyo that the Soviet Union had broken the neutrality pact and declared war on Japan. The senior leadership of the Japanese Army took the news in stride, grossly underestimating the scale of the attack. They did start preparations to impose martial law on the nation, with the support of Minister of War Anami, in order to stop anyone attempting to make peace.

Responsibility for the timing of the second bombing was delegated to Colonel Tibbets as commander of the 509th Composite Group on Tinian. Scheduled for August 11 against Kokura, the raid was moved forward to avoid a five day period of bad weather forecast to begin on the 10th.


Urakami Tenshudo (Catholic Church in Nagasaki) destroyed by the atomic bomb, the dome of the church having toppled off.

The city of Nagasaki had been one of the largest sea ports in southern Japan and was of great wartime importance because of its wide-ranging industrial activity, including the production of ordnance, ships, military equipment, and other war materials.

In contrast to many modern aspects of Nagasaki, the bulk of the residences were of old-fashioned Japanese construction, consisting of wood or wood-frame buildings, with wood walls (with or without plaster), and tile roofs. Many of the smaller industries and business establishments were also housed in buildings of wood or other materials not designed to withstand explosions. Nagasaki had been permitted to grow for many years without conforming to any definite city zoning plan; residences were erected adjacent to factory buildings and to each other almost as closely as possible throughout the entire industrial valley.

Nagasaki had never been subjected to large-scale bombing prior to the explosion of a nuclear weapon there. On August 1, 1945, however, a number of conventional high-explosive bombs were dropped on the city. A few hit in the shipyards and dock areas in the southwest portion of the city, several hit the Mitsubishi Steel and Arms Works and six bombs landed at the Nagasaki Medical School and Hospital, with three direct hits on buildings there. While the damage from these bombs was relatively small, it created considerable concern in Nagasaki and a number of people—principally school children—were evacuated to rural areas for safety, thus reducing the population in the city at the time of the nuclear attack.

To the north of Nagasaki there was a camp holding British prisoners of war. They were working in the coal mines so consequently only found out about the bombing when they came to the surface. For them, it was the bomb that saved their lives. However at least eight known POWs were causalities.

The bombing

A Japanese report on the bombing characterized Nagasaki as "like a graveyard with not a tombstone standing."

On the morning of August 9, 1945, the crew of the American B-29 Superfortress Bock's Car, flown by Major Charles W. Sweeney and carrying the nuclear bomb code-named "Fat Man," found their primary target, Kokura, to be obscured by clouds. After three runs over the city and having fuel running low due to a fuel-transfer problem, they headed for their secondary target, Nagasaki. At about 07:50 Japanese time, an air raid alert was sounded in Nagasaki, but the "all clear" signal was given at 08:30. When only two B-29 Superfortresses were sighted at 10:53 the Japanese apparently assumed that the planes were only on reconnaissance and no further alarm was given.

A few minutes later, at 11:00, the observation B-29 (The Great Artiste flown by Captain Frederick C. Bock) dropped instruments attached to three parachutes. These instruments also contained messages to Prof. Ryokichi Sagane, a nuclear physicist at the University of Tokyo who studied with three of the scientists responsible for the atomic bomb at the University of California, Berkeley, urging him to tell the public about the danger involved with these weapons of mass destruction. The messages were found by military authorities, but not turned over to Sagane.

A post-war "Fat Man" model

The hibakusha

The survivors of the bombings are called hibakusha (被爆者), a Japanese word that literally translates to "people exposed to the bomb". The suffering of the bombing is the root of Japan's postwar pacifism, and the nation has sought the abolition of nuclear weapons from the world ever since. As of 2006, there are about 266,000 hibakusha still living in Japan.