Geo436 Featured Report: During the final stages of World War II in 1945, the United States conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan.
After six months of intense strategic fire-bombing of 67 Japanese cities the Japanese government ignored an ultimatum given by the Potsdam Declaration. By executive order of President Harry S. Truman the U.S. dropped the nuclear weapon “Little Boy” on the city of Hiroshima on Monday, August 6, 1945,followed by the detonation of “Fat Man” over Nagasaki on August 9. These two events are the only active deployments of nuclear weapons in war. The target of Hiroshima was a city of considerable military importance, containing Japan’s Second Army Headquarters, as well as being a communications center and storage depot.
Within the first two to four months of the bombings, the acute effects killed 90,000–166,000 people in Hiroshima and 60,000–80,000 in Nagasaki, with roughly half of the deaths in each city occurring on the first day. The Hiroshima prefectural health department estimates that, of the people who died on the day of the explosion, 60% died from flash or flame burns, 30% from falling debris and 10% from other causes. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness. In a more plausible estimate of the total immediate and short term cause of death, 15–20% died from radiation sickness, 20–30% from flash burns, and 50–60% from other injuries, compounded by illness. In both cities, most of the dead were civilians.
Six days after the detonation over Nagasaki, on August 15, Japan announced its surrender to the Allied Powers, signing the Instrument of Surrender on September 2, officially ending the Pacific War and therefore World War II. Germany had signed its Instrument of Surrender on May 7, ending the war in Europe. The bombings led, in part, to post-war Japan adopting Three Non-Nuclear Principles, forbidding the nation from nuclear armament. The role of the bombings in Japan’s surrender and the U.S.’s ethical justification for them, as well as their strategical importance, is still debated.
Hiroshima
Hiroshima during World War II
At the time of its bombing, Hiroshima was a city of some industrial and military significance. A number of military camps were located nearby, including the headquarters of the Fifth Division and Field Marshal Shunroku Hata’s 2nd General Army Headquarters, which commanded the defense of all of southern Japan. Hiroshima was a minor supply and logistics base for the Japanese military. The city was a communications center, a storage point, and an assembly area for troops. It was one of several Japanese cities left deliberately untouched by American bombing, allowing a pristine environment to measure the damage caused by the atomic bomb.
The center of the city contained several reinforced concrete buildings and lighter structures. Outside the center, 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 constructed of wood with tile roofs, and many of the industrial buildings were also built around wood frames. 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 340,000–350,000. Because official documents were burned, the exact population is uncertain.
The bombing
For the composition of the USAAF mission, see 509th Operations Group#Components.
Hiroshima was the primary target of the first nuclear bombing mission on August 6, with Kokura and Nagasaki being alternative targets. August 6 was chosen because clouds had previously obscured the target. The 393d Bombardment Squadron B-29 Enola Gay, piloted and commanded by 509th Composite Group commander Colonel Paul Tibbets, was launched from North Field airbase on Tinian in the West Pacific, about six hours flight time from Japan. The Enola Gay(named after Colonel Tibbets’ mother) was accompanied by two other B29s. The Great Artiste, commanded by Major Charles W. Sweeney, carried instrumentation; and a then-nameless aircraft later called Necessary Evil (the photography aircraft) was commanded by Captain George Marquardt.
After leaving Tinian the aircraft made their way separately to Iwo Jima where they rendezvoused at 2,440 meters (8,010 ft) and set course for Japan. The aircraft arrived over the target in clear visibility at 9,855 meters (32,333 ft). During the journey, Navy Captain William Parsons had armed the bomb, which had been left unarmed to minimize the risks during takeoff. His assistant, 2nd Lt. Morris Jeppson, removed the safety devices 30 minutes before reaching the target area.
About an hour before the bombing, Japanese early warning radar detected the approach of some American aircraft headed for the southern part of Japan. An alert was given and radio broadcasting stopped in many cities, among them Hiroshima. 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 conserve fuel and aircraft, the Japanese had decided not to intercept small formations. 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.
The release at 08:15 (Hiroshima time) went as planned, and the gravity bomb known as “Little Boy”, agun-type fission weapon with 60 kilograms (130 lb) of uranium-235, took 43 seconds to fall from the aircraft to the predetermined detonation height about 1,900 feet (580 m) above the city. The site also states that the aircraft had traveled 11.5 miles away before it felt the shock waves from the blast.
Due to crosswind, it missed the aiming point, the Aioi Bridge, by almost 800 feet (240 m) and detonated directly over Shima Surgical Clinic. It created a blast equivalent to about 13 kilotons of TNT (54 TJ). (The U-235 weapon was considered very inefficient, with only 1.38% of its material fissioning.) The radius of total destruction was about one mile (1.6 km), with resulting fires across 4.4 square miles (11 km2). Americans estimated that 4.7 square miles (12 km2) of the city were destroyed. Japanese officials determined that 69% of Hiroshima’s buildings were destroyed and another 6–7% damaged.
70,000–80,000 people, or some 30% of the population of Hiroshima were killed immediately, and another 70,000 injured. Over 90% of the doctors and 93% of the nurses in Hiroshima were killed or injured—most had been in the downtown area which received the greatest damage.
Although the U.S. had previously dropped leaflets warning civilians of air raids on 35 Japanese cities, including Hiroshima and Nagasaki, the residents of Hiroshima were given no notice of the atomic bomb.
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 20 minutes later the Tokyo railroad telegraph center realized that the main line telegraph had stopped working just north of Hiroshima. From some small railway stops within 16 kilometers (10 mi) of the city came unofficial and confused reports of a terrible explosion in Hiroshima. All these reports were transmitted to the headquarters of the Imperial Japanese Army 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 and that the explosion was just a rumor.
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.
By August 8, 1945, newspapers in the U.S. were reporting that broadcasts from Radio Tokyo had described the destruction observed in Hiroshima. “Practically all living things, human and animal, were literally seared to death,” Japanese radio announcers said in a broadcast received by Allied sources.
Post-attack casualties
According to the US Department of Energy the immediate effects of the blast killed approximately 70,000 people in Hiroshima and 40,000 in Nagasaki. Estimates of total deaths by the end of 1945 from burns, radiation and related disease, the effects of which were aggravated by lack of medical resources, range from 90,000 to 166,000. Some estimates state up to 200,000 had died by 1950, due to cancer and other long-term effects. Another study states that from 1950 to 1990, roughly 9% of the cancer and leukemia deaths among bomb survivors was due to radiation from the bombs, the statistical excess being estimated to 89 leukemia and 339 solid cancers. At least eleven known prisoners of war died from the bombing.
Survival of some structures
Some of the reinforced concrete buildings in Hiroshima had been very strongly constructed because of the earthquake danger in Japan, and their framework did not collapse even though they were fairly close to the blast center. Eizo Nomura (野村 英三 Nomura Eizō) was the closest known survivor, who was in the basement of a reinforced concrete building (it remained as the “Rest House” after the war) only 100 m (330 ft) from ground-zero at the time of the attack. Akiko Takakura (高蔵 信子 Takakura Akiko) was among the closest survivors to the hypocenter of the blast. She had been in the solidly built Bank of Hiroshima only 300 meters (980 ft) from ground-zero at the time of the attack. Since the bomb detonated in the air, the blast was directed 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. This building was designed and built by the Czech architect Jan Letzel, and was only 150 m (490 ft) from ground zero (the hypocenter). The ruin was named Hiroshima Peace Memorial and was made a UNESCO World Heritage site in 1996 over the objections of the U.S. and China. The Memorial monument for Hiroshima was built in Hiroshima for bombing victims.
Nagasaki
Nagasaki during World War II
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 Hiroshima, almost all of the buildings 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 situated 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 theNagasaki 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 many 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 Commonwealth prisoners of war, some of whom were working in the coal mines and only found out about the bombing when they came to the surface.
The bombing
For the composition of the USAAF mission, see 509th Operations Group#Components.
On the morning of August 9, 1945, the U.S. B-29 Superfortress Bockscar, flown by the crew of 393rd Squadron commander Major Charles W. Sweeney, carried the nuclear bomb code-named “Fat Man”, with Kokura as the primary target and Nagasaki the secondary target. The mission plan for the second attack was nearly identical to that of the Hiroshima mission, with two B-29s flying an hour ahead as weather scouts and two additional B-29s in Sweeney’s flight for instrumentation and photographic support of the mission. Sweeney took off with his weapon already armed but with the electrical safety plugs still engaged.
Observers aboard the weather planes reported both targets clear. When Sweeney’s aircraft arrived at the assembly point for his flight off the coast of Japan, the third plane, Big Stink, flown by the group’s Operations Officer, Lt. Col. James I. Hopkins, Jr. failed to make the rendezvous. Bockscar and the instrumentation plane circled for 40 minutes without locating Hopkins. Already 30 minutes behind schedule, Sweeney decided to fly on without Hopkins.
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By the time they reached Kokura a half hour later, a 70% cloud cover had obscured the city, prohibiting the visual attack required by orders. After three runs over the city, and with fuel running low because a transfer pump on a reserve tank had failed before take-off, they headed for their secondary target, Nagasaki. Fuel consumption calculations made en route indicated that Bockscar had insufficient fuel to reach Iwo Jima and would be forced to divert to Okinawa. After initially deciding that if Nagasaki were obscured on their arrival the crew would carry the bomb to Okinawa and dispose of it in the ocean if necessary, the weaponeer Navy Commander Frederick Ashworth decided that a radar approach would be used if the target was obscured.
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 Great Artiste, the support B-29 flown by Captain Frederick C. Bock, dropped instruments attached to three parachutes. These instruments also contained an unsigned letter to Professor 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 until a month later. In 1949, one of the authors of the letter, Luis Alvarez, met with Sagane and signed the document.
At 11:01, a last minute break in the clouds over Nagasaki allowed Bockscar’s bombardier, CaptainKermit Beahan, to visually sight the target as ordered. The “Fat Man” weapon, containing a core of ~6.4 kg (14.1 lbs.) of plutonium-239, was dropped over the city’s industrial valley. It exploded 43 seconds later at 469 meters (1,540 ft) above the ground exactly halfway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works (Torpedo Works) in the north. This was nearly 3 kilometers (2 mi) northwest of the planned hypocenter; the blast was confined to the Urakami Valley and a major portion of the city was protected by the intervening hills. The resulting explosion had a blast yield equivalent to 21 kilotons of TNT (88 TJ). The explosion generated heat estimated at 3,900 degrees Celsius (4,200 K, 7,000 °F) and winds that were estimated at 1005 km/h (624 mph).
Casualty estimates for immediate deaths range from 40,000 to 75,000. Total deaths by the end of 1945 may have reached 80,000. At least eight known POWs died from the bombing and as many as 13 POWs may have died:
- One British Commonwealth citizen died in the bombing.
- Seven Dutch POWs (two names known) died in the bombing.
- At least two POWs reportedly died postwar from cancer thought to have been caused by the atomic bomb.
The radius of total destruction was about a mile (1–2 km), followed by fires across the northern portion of the city to two miles (3 km) south of the bomb.
One American POW, Joe Kieyoomia, was in Nagasaki at the time of the bombing but survived, reportedly having been shielded from the effects of the bomb by the concrete walls of his cell.
An unknown number of survivors from the Hiroshima bombing had made their way to Nagasaki, where they were bombed again.
The Mitsubishi-Urakami Ordnance Works, the factory that manufactured the type 91 torpedoes released in Pearl Harbor, was subsequently destroyed in the blast.
There is also a peace monument and Bell of Nagasaki in the Kokura.
Plans for more atomic attacks on Japan
The U.S. expected to have another atomic bomb ready for use in the third week of August, with three more in September and a further three in October. On August 10, Major General Leslie Groves, military director of the Manhattan Project, sent a memorandum to General of the Army George Marshall, Army Chief of Staff, in which he wrote that “the next bomb . . should be ready for delivery on the first suitable weather after 17 or August 18.” On the same day, Marshall endorsed the memo with the comment, “It is not to be released over Japan without express authority from the President.” There was already discussion in the War Department about conserving the bombs in production until Operation Downfall, the projected invasion of Japan, had begun. “The problem now [August 13] is whether or not, assuming the Japanese do not capitulate, to continue dropping them every time one is made and shipped out there or whether to hold them . . . and then pour them all on in a reasonably short time. Not all in one day, but over a short period. And that also takes into consideration the target that we are after. In other words, should we not concentrate on targets that will be of the greatest assistance to an invasion rather than industry, morale, psychology, and the like? Nearer the tactical use rather than other use.”
Depiction and Public response
During the war “annihilationist and exterminationalist rhetoric” was tolerated at all levels of U.S. society; according to the UK embassy in Washington the Americans regarded the Japanese as “a nameless mass of vermin”. Caricatures depicting Japanese as less than human, e.g. monkeys, were common. A 1944 opinion poll that asked what should be done with Japan found that 13% of the U.S. public were in favor of the extermination of all Japanese, men women and children.
News of the atomic bombing were greeted enthusiastically in the U.S.; a poll in Fortune magazine in late 1945 showed a significant minority of Americans wishing that more atomic bombs could have been dropped on Japan. The initial positive response was supported by the imagery presented to the public, (mainly the powerful mushroom cloud) and the absence of evidence of the human effects—photographs showing corpses and maimed survivors—were suppressed, and reports were censored. As an example, a member of the U.S. Strategic Bombing Survey, Lieutenant Daniel McGovern, used a film crew to document the results. The film crew’s work resulted in a three-hour documentary entitled The Effects of the Atomic Bombs Against Hiroshima and Nagasaki. The documentary included images from hospitals showing the human effects of the bomb; it showed burned out buildings and cars, and rows of skulls and bones on the ground. When sent to the U.S., it was mentioned widely in the U.S. press, then quietly suppressed and never shown. It was classified “top secret” for the next 22 years.
Imagery of the atomic bombings was suppressed in Japan during the occupation although some Japanese magazines had managed to publish images before the Allied occupation troops took control. The Allied occupation forces enforced censorship on anything “that might, directly or by inference, disturb public tranquility”, and pictures of the effects of the people on the ground were deemed inflammatory. A likely reason for the banning was that the images depicting burn victims and funeral pyres evoked similarities to the widely circulated images taken in liberated Nazi concentration camps.
Atomic Bomb Casualty Commission
In the spring of 1948, the Atomic Bomb Casualty Commission (ABCC) was established in accordance with a presidential directive from Harry S. Truman to the National Academy of Sciences-National Research Council to conduct investigations of the late effects of radiation among the survivors in Hiroshima and Nagasaki.
Among the casualties were found many unintended victims, including Allied POWs, Korean and Chinese laborers, students from Malaya on scholarships, and some 3,200 Japanese American citizens.
One of the early studies conducted by the ABCC was on the outcome of pregnancies occurring in Hiroshima and Nagasaki, and in a controlcity, Kure located 18 miles (29 km) south from Hiroshima, in order to discern the conditions and outcomes related to radiation exposure. One author has claimed that the ABCC refused to provide medical treatment to the survivors for better research results. In 1975, the Radiation Effects Research Foundation was created to assume the responsibilities of ABCC
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