The United States detonated two nuclear weapons over the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945, respectively, with the consent of the United Kingdom, as required by the Quebec Agreement. The two bombings killed between 129,000 and 226,000 people, most of whom were civilians, and remain the only uses of nuclear weapons in armed conflict ever.
In the final year of World War II, the Allies prepared for a very costly invasion of the Japanese mainland. This undertaking was preceded by a conventional and firebombing campaign which devastated 67 Japanese cities. The war in Europe had concluded when Germany signed its instrument of surrender on May 8, 1945, and the Allies turned their full attention to the Pacific theater. The Allies called for the unconditional surrender of the Imperial Japanese armed forces in the Potsdam Declaration on July 26, 1945, the alternative being “prompt and utter destruction.” Japan ignored the ultimatum and the war continued.
By August 1945, the Allies’ Manhattan Project had produced two types of atomic bombs, and the 509th Composite Group of the United States Army Air Forces (USAAF) was equipped with the specialized Silver-plate version of the Boeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. The Allies issued orders for atomic bombs to be used on four Japanese cities on July 25. On August 6, one of the modified B-29s dropped a uranium gun-type bomb (“Little Boy”) on Hiroshima. Another B-29 dropped a plutonium implosion bomb (“Fat Man”) on Nagasaki three days later. The bombs immediately devastated their targets. Over the next two to four months, the acute effects of the atomic bombings killed between 90,000 and 146,000 people in Hiroshima and 39,000 and 80,000 people in Nagasaki; roughly half of the deaths in each city occurred on the first day. Large numbers of people continued to die for months afterward from the effects of burns, radiation sickness, and other injuries, compounded by illness and malnutrition. In both cities, most of the dead were civilians, although Hiroshima had a sizable military garrison.
Japan surrendered to the Allies on August 15, six days after the Soviet Union’s declaration of war and the bombing of Nagasaki. The Japanese government signed the instrument of surrender on September 2 in Tokyo Bay, which effectively ended World War II. The effects of the bombings on the social and political character of subsequent world history and ethical and legal justification for the bombings is still debated after 75 years.
Allies Vs Japan – Pacific War (1945)
In 1945, the Pacific War between Japan and the Allies was in the fourth year. Japanese continued to fight fiercely, at great cost to the Allies. The United States incurred nearly 1.25 million battle casualties in WW II, both military personnel killed or wounded in action. Nearly one million of these occurred during the last year of the war, from June 1944 to June 1945. America’s reserves of manpower were running out. Also the public was becoming war-weary, and demanding that long-serving servicemen be sent home.
In April 1945, American forces landed on Okinawa, where heavy fighting continued until June. Along the way, the ratio of Japanese to American casualties dropped from 5:1 in the Philippines to 2:1 on Okinawa. Although some Japanese soldiers were taken prisoner, most fought until they were killed or committed suicide. As the Allies advanced towards Japan, conditions became steadily worse for the Japanese people. Lack of raw materials forced the Japanese war economy into a steep decline after the middle of 1944. By 1943, the U.S. produced almost 100,000 aircraft a year, compared to Japan’s production of 70,000 for the entire war. By the middle of 1944, the U.S. had almost a hundred aircraft carriers in the Pacific, far more than Japan’s twenty-five for the entire war. In February 1945, Prince Fumimaro Konoe advised Emperor Hirohito that defeat was inevitable, and urged him to abdicate.
Nazi Germany Surrenders – Japan Holds On
Even before the surrender of Nazi Germany on May 8, 1945, plans were underway for the largest operation of the Pacific War, Operation Downfall, the Allied invasion of Japan. Set to begin in October 1945, it involved a series of landings by the U.S. Sixth Army intended to capture the southern third of the southernmost main Japanese island, Kyūshū. The dates were chosen to allow for troops to be redeployed from Europe.
Japan’s geography made this invasion plan obvious to the Japanese; they were able to predict the Allied invasion plans accurately and thus adjust their defensive plan, Operation Ketsugō, accordingly. The Japanese planned an all-out defense of Kyūshū, with little left in reserve for any subsequent defense operations. Four veteran divisions were withdrawn from Manchuria in March 1945 to strengthen the forces in Japan, and 45 new divisions were activated between February and May 1945. Most were immobile formations for coastal defense, but 16 were high quality mobile divisions. In all, there were 2.3 million Japanese Army troops prepared to defend the home islands, backed by a civilian militia of 28 million men and women. The Vice Chief of the Imperial Japanese Navy General Staff, Vice Admiral Takijirō Ōnishi, predicted up to 20 million Japanese deaths.
US Plan For Operation Downfall – High Casualty Estimates
On June 15, 1945, a study by the US Joint War Plans Committee, informed the Joint Chiefs of Staff, estimated that the US Operation would result in 130,000 to 220,000 U.S. casualties, with U.S. dead in the range from 25,000 to 46,000. The Chief of Staff of the United States Army, General of the Army George Marshall, and the Army Commander in Chief in the Pacific, General of the Army Douglas MacArthur, signed documents agreeing with the Joint War Plans Committee estimate.
Plan to Use Chemical and Biological Weapons
The Americans were alarmed by the Japanese buildup, and the estimates of the US casualties. Marshall began contemplating the use of a weapon that was “readily available and which assuredly can decrease the cost in American lives”: poison gas. Quantities of phosgene, mustard gas, tear gas and cyanogen chloride were moved to Luzon from stockpiles in Australia and New Guinea. MacArthur ensured that Chemical Warfare Service units were trained in their use. Consideration was also given to using biological weapons against Japan.
Air raids on Japan – Lack of Success
Operation Matterhorn involved India-based B-29s staging through bases around Chengdu in China to make a series of raids on strategic targets in Japan. This effort failed to achieve the strategic objectives that its planners had intended, largely because of logistical problems, the bomber’s mechanical difficulties, the vulnerability of Chinese staging bases, and the extreme range required to reach key Japanese cities. It was decided to use Guam, Tinian, and Saipan in the Mariana Islands would better serve as B-29 bases, but they were in Japanese hands. Strategies were shifted to accommodate the air war, and the islands were captured between June and August 1944. Air bases were developed, and B-29 operations commenced from the Marianas in October 1944. The XXI Bomber Command began missions against Japan on November 18, 1944. The early attempts to bomb Japan from the Marianas proved just as ineffective as the China-based B-29s had been.
Bombardment with Incendiaries
Washington, changed tactics and decided that low-level incendiary raids against Japanese cities were the only way to destroy their production capabilities, shifting from precision bombing to area bombardment with incendiaries. Like most strategic bombing during World War II, the aim of the air offensive against Japan was to destroy the enemy’s war industries, kill or disable civilian employees of these industries, and undermine civilian morale. Over the next six months, the Bomber Command firebombed 67 Japanese cities. The firebombing of Tokyo, codenamed Operation Meetinghouse, on March 9–10 killed an estimated 100,000 people and destroyed 16 square miles (41 km2) of the city and 267,000 buildings in a single night. It was the deadliest bombing raid of the war, at a cost of 20 B-29s shot down by flak and fighters. By May, 75% of bombs dropped were incendiaries designed to burn down Japan’s “paper cities”. By mid-June, Japan’s six largest cities had been devastated. The end of the fighting on Okinawa that month provided airfields even closer to the Japanese mainland, allowing the bombing campaign to be further escalated. Aircraft flying from Allied aircraft carriers and the Ryukyu Islands also regularly struck targets in Japan during 1945 in preparation for Operation Downfall. Firebombing switched to smaller cities, with populations ranging from 60,000 to 350,000. The Japanese military was unable to stop the Allied attacks and the country’s civil defense preparations proved inadequate. By mid-1945 the Japanese only occasionally scrambled aircraft to intercept individual B-29s conducting reconnaissance sorties over the country, to conserve both aircraft and fuel.
Atomic Bomb Development – Project Manhattan
The discovery of nuclear fission by German chemists Otto Hahn and Fritz Strassmann in 1938, and its theoretical explanation by Lise Meitner and Otto Frisch, made the development of an atomic bomb a theoretical possibility. There were fears that a German atomic bomb project would develop atomic weapons first, especially among scientists who were refugees from Nazi Germany. This prompted preliminary research in the United States in late 1939. The 1943 Quebec Agreement merged the nuclear weapons projects of the United Kingdom and Canada, Tube Alloys and the Montreal Laboratory, with the Manhattan Project, under the direction of Major General Leslie R. Groves, Jr., of the U.S. Army Corps of Engineers. Groves appointed J. Robert Oppenheimer to organize and head the project’s Los Alamos Laboratory in New Mexico, where bomb design work was carried out. Two types of bombs were eventually developed, both named by Robert Serber. Little Boy was a gun-type fission weapon that used uranium-235, a rare isotope of uranium. The other, known as a Fat Man device, was a more powerful and efficient, but more complicated, implosion-type nuclear weapon that used plutonium created in nuclear reactors. There was a Japanese nuclear weapon program, but it lacked the human, mineral and financial resources of the Manhattan Project, and never made much progress towards developing an atomic bomb.
Preparations For Delivery
The 509th Composite Group was constituted on December 9, 1944, and activated on December 17, 1944, at Wendover Army Air Field, Utah, commanded by Colonel Paul Tibbets. Tibbets was assigned to organize and command a combat group to develop the means of delivering an atomic weapon against targets in Germany and Japan. Because the flying squadrons of the group consisted of both bomber and transport aircraft, the group was designated as a “composite” rather than a “bombardment” unit. Working with the Manhattan Project at Los Alamos, Tibbets selected Wendover for his training base because of its remoteness. Each bombardier completed at least 50 practice drops of inert or conventional explosive pumpkin bombs and Tibbets declared his group combat-ready. On April 5, 1945, the code name Operation Centerboard was assigned. The officer responsible for its allocation in the War Department’s Operations Division was not cleared to know any details of it. The first bombing was later codenamed Operation Centerboard I, and the second, Operation Centerboard II.
509th Composite Group Moves To Launch Base
The 509th Composite Group had an authorized strength of 225 officers and 1,542 enlisted men, almost all of whom eventually deployed to Tinian. They also had 51 civilian and military personnel from Project Alberta, known as the 1st Technical Detachment. Group’s 393d Bombardment Squadron was equipped with 15 Silverplate B-29s. These aircraft were specially adapted to carry nuclear weapons, and were equipped with fuel-injected engines, Curtiss Electric reversible-pitch propellers, pneumatic actuators for rapid opening and closing of bomb bay doors and other improvements. The ground support echelon of the Group moved by rail on April 26, 1945, to its port of embarkation at Seattle, Washington. On May 6 the support elements sailed on the SS Cape Victory for the Marianas, while group materiel was shipped on the SS Emile Berliner.
An advance party of the air echelon, consisting of 29 officers and 61 enlisted men flew by C-54 to North Field on Tinian, between May 15 and May 22. There were also two representatives from Washington, D.C., who were on hand to decide higher policy matters on the spot. Along with Captain William S. Parsons, the commander of Project Alberta, they became known as the “Tinian Joint Chiefs“.
The Targets Selection
In April 1945, Marshall asked Groves to nominate specific targets for bombing for final approval by himself and Stimson. Groves formed and chaired a “Target Committee” that met in Washington on April 27; at Los Alamos on May 10, where it was able to talk to the scientists and technicians there; and finally in Washington on May 28, where it was briefed by Tibbets and Commander 509th Composite Group Frederick Ashworth from Project Alberta, and the Manhattan Project’s scientific advisor, Richard C. Tolman. The Target Committee nominated five targets: Kokura (now Kitakyushu), the site of one of Japan’s largest munitions plants; Hiroshima, an embarkation port and industrial center that was the site of a major military headquarters; Yokohama, an urban center for aircraft manufacture, machine tools, docks, electrical equipment and oil refineries; Niigata, a port with industrial facilities including steel and aluminum plants and an oil refinery; and Kyoto, a major industrial center. The target selection criteria was that the target be larger than 3 mi (4.8 km) in diameter and was an important target in a large city. The blast would create effective damage. The target was unlikely to be attacked by August 1945. Nagasaki Came up Later.
These cities were largely untouched during the nightly bombing raids, and the Army Air Forces agreed to leave them off the target list so accurate assessment of the damage caused by the atomic bombs could be made. Hiroshima was described as “an important army depot and port of embarkation in the middle of an urban industrial area. It is a good radar target and it is such a size that a large part of the city could be extensively damaged. There are adjacent hills which are likely to produce a focusing effect which would considerably increase the blast damage. Due to rivers it is not a good incendiary target.”
The Target Committee stated that “It was agreed that psychological factors in the target selection were of great importance. Two aspects of this are (1) obtaining the greatest psychological effect against Japan and (2) making the initial use sufficiently spectacular for the importance of the weapon to be internationally recognized when publicity on it is released. Kyoto had the advantage of the people being more highly intelligent and hence better able to appreciate the significance of the weapon. Hiroshima had the advantage of being such a size and with possible focusing from nearby mountains that a large fraction of the city may be destroyed. The Emperor’s palace in Tokyo had a greater fame than any other target but is of least strategic value.”
On May 30, Stimson asked Groves to remove Kyoto from the target list due to its historical, religious and cultural significance, but Groves pointed to its military and industrial significance. Stimson then approached President Harry S. Truman about the matter. Truman agreed with Stimson, and Kyoto was temporarily removed from the target list. Groves attempted to restore Kyoto to the target list in July, but Stimson remained adamant. On July 25, Nagasaki was put on the target list in place of Kyoto. It was a major military port, one of Japan’s largest shipbuilding and repair centers, and an important producer of naval ordnance.
Proposed Non-Combat Demonstration
During the meetings on May 31 and June 1, it was suggested giving the Japanese a non-combat demonstration. But views against it were significant. If a bomb were exploded in Japan with previous notice, the Japanese air power was still adequate to give serious interference. An atomic bomb was an intricate device, still in the developmental stage. Its operation would be far from routine. If during the final adjustments of the bomb the Japanese defenders should attack, a faulty move might easily result in some kind of failure. Such an end to an advertised demonstration of power would be much worse than if the attempt had not been made. US could not afford the chance that one of them might be a dud. If the test were made on some neutral territory, it was hard to believe that Japan’s determined and fanatical military men would be impressed. If such an open test were made first and failed to bring surrender, the chance would be gone to give the shock of surprise that proved so effective. On the contrary, it would make the Japanese ready to interfere with an atomic attack if they could. Though the possibility of a demonstration that would not destroy human lives was attractive, no one could suggest a way in which it could be made so convincing that it would be likely to stop the war.
Warning Leaflets – Psychological Warfare
For several months, the U.S. had warned civilians of potential air raids by dropping more than 63 million leaflets across Japan. Many Japanese cities suffered terrible damage from aerial bombings; some were as much as 97% destroyed. It was thought that leaflets would increase the psychological impact of bombing, and reduce the international stigma of area-bombing cities. Many Japanese regarded the leaflet messages as truthful, and some chose to leave major cities. The leaflets caused such concern that the government ordered the arrest of anyone caught in possession of a leaflet. Leaflet texts were prepared by recent Japanese prisoners of war because they were thought to be the best choice “to appeal to their compatriots”. In final preparation for dropping an atomic bomb on Hiroshima, it was decided against any special leaflet warning. There was uncertainty of a successful detonation and also because of the wish to maximize shock on the leadership. No warning was given to Hiroshima that a new and much more destructive bomb was going to be dropped. Various sources gave conflicting information about when the last leaflets were dropped on Hiroshima prior to the atomic bomb. The USAAF history notes that eleven cities were targeted with leaflets on July 27, but Hiroshima was not one of them, and there were no leaflet sorties on July 30. Leaflet sorties were undertaken on August 1 and August 4. Leaflets listed up to a total of 33 cities. Hiroshima was not listed.
Final Consultation with Britain and Canada
In 1943, The United States and the United Kingdom signed the Quebec Agreement, which stipulated that nuclear weapons would not be used against another country without mutual consent. Stimson therefore had to obtain British permission. A meeting of the Combined Policy Committee, which included one Canadian representative, was held at the Pentagon on July 4, 1945. The British government concurred with the use of nuclear weapons against Japan, which would be officially recorded as a decision of the Combined Policy Committee. As the release of information to third parties was also controlled by the Quebec Agreement, discussion then turned to what scientific details would be revealed in the press announcement of the bombing. The meeting also considered what Truman could reveal to Joseph Stalin, the leader of the Soviet Union, at the upcoming Potsdam Conference, as this also required British concurrence.
Final Orders For the Atomic Attack
Orders for the attack were issued to General Carl Spaatz on July 25 under the signature of General Thomas T. Handy, the acting Chief of Staff, since Marshall was at the Potsdam Conference with Truman. It read:
The 509th Composite Group, 20th Air Force will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August 1945 on one of the targets: Hiroshima, Kokura, Niigata and Nagasaki. To carry military and civilian scientific personnel from the War Department to observe and record the effects of the explosion of the bomb, additional aircraft will accompany the airplane carrying the bomb. The observing planes will stay several miles distant from the point of impact of the bomb. Additional bombs will be delivered on the above targets as soon as made ready by the project staff. Further instructions will be issued concerning targets other than those listed above.
That day, Truman noted in his diary that: This weapon is to be used against Japan between now and August 10th. I have told the Sec. of War, Mr. Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless and fanatic, we as the leader of the world for the common welfare cannot drop that terrible bomb on the old capital [Kyoto] or the new [Tokyo]. He and I are in accord. The target will be a purely military one.
Potsdam Declaration – Ultimatum to Japan
The July 16 success of the Trinity Test in the New Mexico desert exceeded expectations. On July 26, Allied leaders issued the Potsdam Declaration, which outlined the terms of surrender for Japan. The declaration was presented as an ultimatum and stated that without a surrender, the Allies would attack Japan, resulting in “the inevitable and complete destruction of the Japanese armed forces and just as inevitably the utter devastation of the Japanese homeland”. The atomic bomb was not mentioned in the communiqué.
Japanese Ignore Ultimatum
On July 28, Japanese papers reported that the declaration had been rejected by the Japanese government. That afternoon, Prime Minister Suzuki Kantarō declared at a press conference that the Potsdam Declaration was no more than a rehash (yakinaoshi) of the Cairo Declaration and that the government intended to ignore it (mokusatsu, “kill by silence”). The statement was taken by both Japanese and foreign papers as a clear rejection of the declaration. Emperor Hirohito, who was waiting for a Soviet reply to non-committal Japanese peace feelers, made no move to change the government position. Japan’s willingness to surrender remained conditional on the preservation of the kokutai (Imperial institution and national polity), assumption by the Imperial Headquarters of responsibility for disarmament and demobilization, no occupation of the Japanese Home Islands, Korea or Formosa, and delegation of the punishment of war criminals to the Japanese government.
British Request Representation in Mission
At Potsdam, Truman agreed to a request from Winston Churchill that Britain be represented when the atomic bomb was dropped. William Penney and Group Captain Leonard Cheshire were sent to Tinian, but found that LeMay would not let them accompany the mission. All they could do was send a strongly worded signal to Wilson.
Bombs and Safeties
The Little Boy bomb, except for the uranium payload, was ready at the beginning of May 1945. There were two uranium-235 components, a hollow cylindrical projectile and a cylindrical target insert. The projectile was completed on June 15, and the target insert on July 24. The projectile and eight bomb pre-assemblies (partly assembled bombs without the powder charge and fissile components) left Hunters Point Naval Shipyard, California, on July 16 aboard the cruiser USS Indianapolis, and arrived on Tinian on July 26. The target insert followed by air on July 30, accompanied by Commander Francis Birch from Project Alberta. Responding to concerns expressed by the 509th Composite Group about the possibility of a B-29 crashing on takeoff, Birch had modified the Little Boy design to incorporate a removable breech plug that would permit the bomb to be armed in flight.
The first plutonium core, along with its polonium-beryllium urchin initiator, was transported in the custody of Project Alberta courier Raemer Schreiber in a magnesium field carrying case designed for the purpose. Magnesium was chosen because it does not act as a tamper. The core departed from Kirtland Army Air Field on a C-54 transport aircraft of the 509th Composite Group’s 320th Troop Carrier Squadron on July 26, and arrived at North Field July 28. Three Fat Man high-explosive pre-assemblies, designated F31, F32, and F33, were picked up at Kirtland on July 28 by three B-29s, two from the 393d Bombardment Squadron plus one from the 216th Army Air Force Base Unit, and transported to North Field, arriving on August 2.
Hiroshima City and Significance and Defences
At the time of its bombing, Hiroshima was a city of industrial and military significance. A number of military units were located nearby, the most important of which was the headquarters of Field Marshal Shunroku Hata’s Second General Army, which commanded the defense of all of southern Japan, and was located in Hiroshima Castle. Hata’s command consisted of some 400,000 men, most of whom were on Kyushu where an Allied invasion was correctly anticipated. Also present in Hiroshima were the headquarters of the 59th Army, the 5th Division and the 224th Division, a recently formed mobile unit. The city was defended by five batteries of 7-cm and 8-cm (2.8 and 3.1 inch) anti-aircraft guns of the 3rd Anti-Aircraft Division, including units from the 121st and 122nd Anti-Aircraft Regiments and the 22nd and 45th Separate Anti-Aircraft Battalions. In total, an estimated 40,000 Japanese military personnel were stationed in the city.
Hiroshima was a supply and logistics base for the Japanese military. The city was a communications center, a key port for shipping, and an assembly area for troops. It was a beehive of war industry, manufacturing parts for planes and boats, for bombs, rifles, and handguns. A few larger industrial plants lay near the outskirts of the city. The houses were constructed of timber with tile roofs, and many of the industrial buildings were also built around timber frames. The city as a whole was highly susceptible to fire damage. It was the second largest city in Japan after Kyoto that was still undamaged by air raids, primarily because it lacked the aircraft manufacturing industry that was the XXI Bomber Command’s priority target. On July 3, the Joint Chiefs of Staff placed it off limits to bombers, along with Kokura, Niigata and Kyoto. 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. Residents wondered why Hiroshima had been spared destruction by firebombing. Some speculated that the city was to be saved for U.S. occupation headquarters, others thought perhaps their relatives in Hawaii and California had petitioned the U.S. government to avoid bombing Hiroshima. More realistic city officials had ordered buildings torn down to create long, straight firebreaks. These continued to be expanded and extended up to the morning of August 6, 1945.
Bombing of Hiroshima – The Mission Details
Hiroshima was the primary target of the first atomic bombing mission on August 6, with Kokura and Nagasaki as alternative targets. The 393d Bombardment Squadron B-29 Enola Gay, named after Tibbets’ mother and piloted by Tibbets, took off from North Field, Tinian, about six hours’ flight time from Japan. Enola Gay was accompanied by two other B-29s: The Great Artiste, commanded by Major Charles Sweeney, which carried instrumentation, and a then-nameless aircraft later called Necessary Evil, commanded by Captain George Marquardt, which served as the photography aircraft.
|Special Mission 13, Primary target Hiroshima, August 6, 1945|
|Aircraft||Pilot||Call Sign||Mission role|
|Straight Flush||Major Claude R. Eatherly||Dimples 85||Weather reconnaissance (Hiroshima)|
|Jabit III||Major John A. Wilson||Dimples 71||Weather reconnaissance (Kokura)|
|Full House||Major Ralph R. Taylor||Dimples 83||Weather reconnaissance (Nagasaki)|
|Enola Gay||Colonel Paul W. Tibbets||Dimples 82||Weapon delivery|
|The Great Artiste||Major Charles W. Sweeney||Dimples 89||Blast measurement instrumentation|
|Necessary Evil||Captain George W. Marquardt||Dimples 91||Strike observation and photography|
|Top Secret||Captain Charles F. McKnight||Dimples 72||Strike spare – did not complete mission|
Take-Off and Set Course
After leaving Tinian, the aircraft made their way separately to Iwo Jima to rendezvous with Sweeney and Marquardt at 05:55 at 9,200 feet (2,800 m), and set course for Japan. The aircraft arrived over the target in clear visibility at 31,060 feet (9,470 m). Parsons, who was in command of the mission, armed the bomb in flight to minimize the risks during takeoff. He had witnessed four B-29s crash and burn at takeoff, and feared that a nuclear explosion would occur if a B-29 crashed with an armed Little Boy on board. His assistant, Second Lieutenant Morris R. Jeppson, removed the safety devices 30 minutes before reaching the target area.
Air Raid Warnings at Hiroshima
During the night of August 5–6, Japanese early warning radar detected the approach of numerous American aircraft headed for the southern part of Japan. Radar detected 65 bombers headed for Saga, 102 bound for Maebashi, 261 en route to Nishinomiya, 111 headed for Ube and 66 bound for Imabari. An alert was given and radio broadcasting stopped in many cities, among them Hiroshima. The all-clear was sounded in Hiroshima at 00:05. About an hour before the bombing, the air raid alert was sounded again, as Straight Flush flew over the city. It broadcast a short message which was picked up by Enola Gay. It read: “Cloud cover less than 3/10th at all altitudes. Advice: bomb primary.” The all-clear was sounded over Hiroshima again at 07:09.
Bomb Drop Over Hiroshima
At 08:09, Tibbets started his bomb run and handed control over to his bombardier, Major Thomas Ferebee. The release at 08:15 (Hiroshima time) went as planned, and the Little Boy containing about 64 kg (141 lb) of uranium-235 took 44.4 seconds to fall from the aircraft flying at about 31,000 feet (9,400 m) to a detonation height of about 1,900 feet (580 m) above the city. Enola Gay traveled 11.5 mi (18.5 km) before it felt the shock waves from the blast.
Due to crosswind, the bomb missed the aiming point, the Aioi Bridge, by approximately 800 ft (240 m) and detonated directly over Shima Surgical Clinic. It released the equivalent energy of 16 kilotons of TNT (67 TJ), ± 2 kt. The weapon was considered very inefficient, with only 1.7% of its material fissioning. The radius of total destruction was about 1 mile (1.6 km), with resulting fires across 4.4 square miles (11 km2). Enola Gay stayed over the target area for two minutes and was ten miles away when the bomb detonated. Only Tibbets, Parsons, and Ferebee knew of the nature of the weapon; the others on the bomber were only told to expect a blinding flash and given black goggles. “It was hard to believe what we saw”, Tibbets told reporters, while Parsons said “the whole thing was tremendous and awe-inspiring … the men aboard with me gasped ‘My God'”. He and Tibbets compared the shockwave to “a close burst of ack-ack fire”.
Events on the Ground
People on the ground reported a a brilliant flash of light, followed by a loud booming sound. Some 70,000–80,000 people, around 30% of the population of Hiroshima at the time, were killed by the blast and resultant firestorm, and another 70,000 were injured. It is estimated that as many as 20,000 Japanese military personnel were killed. U.S. surveys 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.
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. 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 (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 United States and China, which expressed reservations on the grounds that other Asian nations were the ones who suffered the greatest loss of life and property, and a focus on Japan lacked historical perspective. The bombing started intense fires that spread rapidly through timber and paper homes, burning everything in a radius of 2 kilometers (1.2 mi). As in other Japanese cities, the firebreaks proved ineffective.
The air raid warning had been cleared at 07:31, and many people were outside, going about their activities. Eizō Nomura was the closest known survivor, being in the basement of a reinforced concrete building (it remained as the Rest House after the war) only 170 meters (560 ft) from ground zero at the time of the attack. He died in 1982, aged 84. Akiko Takakura was among the closest survivors to the hypocenter of the blast. She was in the solidly-built Bank of Hiroshima only 300 meters (980 ft) from ground-zero at the time of the attack. 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. The hospitals were destroyed or heavily damaged. Nonetheless, by early afternoon the police and volunteers had established evacuation centres at hospitals, schools and tram stations, and a morgue was established in the Asano library.
“Attacked By a New Type of Bomb”
Most elements of the Japanese Second General Army headquarters were undergoing physical training on the grounds of Hiroshima Castle, barely 900 yards (820 m) from the hypocenter. The attack killed 3,243 troops on the parade ground. The communications room of Chugoku Military District Headquarters that was responsible for issuing and lifting air raid warnings was located in a semi-basement in the castle. Yoshie Oka, a Hijiyama Girls High School student who had been mobilized to serve as a communications officer, had just sent a message that the alarm had been issued for Hiroshima and neighboring Yamaguchi, when the bomb exploded. She used a special phone to inform Fukuyama Headquarters (some 100 kilometers (62 mi) away) that “Hiroshima has been attacked by a new type of bomb. The city is in a state of near-total destruction.”
Japanese Immediate Reaction
The Tokyo control operator of the Japan 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 km (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 General Staff; they knew that no large enemy raid had occurred and that no sizable store of explosives was in Hiroshima at that time. A young officer was instructed to fly immediately to Hiroshima, to land, survey the damage, and return to Tokyo with reliable information for the staff. It was felt 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 160 km (100 mi) from Hiroshima, he and his pilot saw a great cloud of smoke from the bomb. After circling the city to survey the damage they landed south of the city, where the staff officer, after reporting to Tokyo, began to organize relief measures. Tokyo’s first indication that the city had been destroyed by a new type of bomb came from President Truman’s announcement of the strike, sixteen hours later.
US President’s Statement – Implicit Warning
After the Hiroshima bombing, Truman issued a statement announcing the use of the new weapon. He stated, “We may be grateful to Providence” that the German atomic bomb project had failed, and that the United States and its allies had “spent two billion dollars on the greatest scientific gamble in history—and won”. Truman then warned Japan: “If they do not now accept our terms, they may expect a rain of ruin from the air, the like of which has never been seen on this earth. Behind this air attack will follow sea and land forces in such numbers and power as they have not yet seen and with the fighting skill of which they are already well aware.” This was a widely broadcast speech picked up by Japanese news agencies.
Japanese Decide to Fight On
The 50,000-watt standard wave station on Saipan, the OWI radio station, broadcast a similar message to Japan every 15 minutes about Hiroshima, stating that more Japanese cities would face a similar fate in the absence of immediate acceptance of the terms of the Potsdam Declaration and emphatically urged civilians to evacuate major cities. Radio Japan, which continued to extoll victory for Japan by never surrendering, had informed the Japanese of the destruction of Hiroshima by a single bomb. Prime Minister Suzuki felt compelled to meet the Japanese press, to whom he reiterated his government’s commitment to ignore the Allies’ demands and fight on.
Soviet Foreign Minister Vyacheslav Molotov had informed Tokyo of the Soviet Union’s unilateral abrogation of the Soviet–Japanese Neutrality Pact on April 5. At two minutes past midnight on August 9, Tokyo time, Soviet infantry, armor, and air forces had launched the Manchurian Strategic Offensive Operation. Four hours later, word reached Tokyo of the Soviet Union’s official declaration of war. The senior leadership of the Japanese Army began preparations to impose martial law on the nation, with the support of Minister of War Korechika Anami, to stop anyone attempting to make peace.
The War Will Go On
On August 7, a day after Hiroshima was destroyed, Dr. Yoshio Nishina and other atomic physicists arrived at the city, and carefully examined the damage. They then went back to Tokyo and told the cabinet that Hiroshima was indeed destroyed by a nuclear weapon. Admiral Soemu Toyoda, the Chief of the Naval General Staff, estimated that no more than one or two additional bombs could be readied, so they decided to endure the remaining attacks, acknowledging “there would be more destruction but the war would go on”. American Magic code-breakers intercepted the cabinet’s messages.
Decision For Second Bomb – Nagaski
Purnell, Parsons, Tibbets, Spaatz, and LeMay met on Guam that same day to discuss what should be done next. Since there was no indication of Japan surrendering, they decided to proceed with dropping another bomb. Parsons said that Project Alberta would have it ready by August 11, but Tibbets pointed to weather reports indicating poor flying conditions on that day due to a storm, and asked if the bomb could be readied by August 9. Parsons agreed to try to do so
City Status – Nagasaki
Nagasaki had been one of the largest seaports 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. The four largest companies in the city were Mitsubishi Shipyards, Electrical Shipyards, Arms Plant, and Steel and Arms Works, which employed about 90% of the city’s labor force, and accounted for 90% of the city’s industry. Although an important industrial city, Nagasaki had been spared from firebombing because its geography made it difficult to locate at night with AN/APQ-13 radar. Unlike the other target cities, Nagasaki had not been placed off limits to bombers by the Joint Chiefs of Staff’s July 3 directive, and was bombed on a small scale five times. During one of these raids on August 1, a number of conventional high-explosive bombs were dropped on the city. A few hit the shipyards and dock areas in the southwest portion of the city, and several hit the Mitsubishi Steel and Arms Works. By early August, the city was defended by the 134th Anti-Aircraft Regiment of the 4th Anti-Aircraft Division with four batteries of 7 cm (2.8 in) anti-aircraft guns and two searchlight batteries.
In contrast to Hiroshima, almost all of the buildings were of old-fashioned Japanese construction, consisting of timber or timber-framed buildings with timber walls (with or without plaster) and tile roofs. Many of the smaller industries and business establishments were also situated in buildings of timber 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. On the day of the bombing, an estimated 263,000 people were in Nagasaki, including 240,000 Japanese residents, 10,000 Korean residents, 2,500 conscripted Korean workers, 9,000 Japanese soldiers, 600 conscripted Chinese workers, and 400 Allied prisoners of war in a camp to the north of Nagasaki.
Mission Details Nagasaki
Responsibility for the timing of the second bombing was delegated to Tibbets. Scheduled for August 11 against Kokura, the raid was moved earlier by two days to avoid a five-day period of bad weather forecast to begin on August 10. Three bomb pre-assemblies had been transported to Tinian, labeled F-31, F-32, and F-33 on their exteriors. On August 8, a dress rehearsal was conducted off Tinian by Sweeney using Bockscar as the drop airplane. Assembly F-33 was expended testing the components and F-31 was designated for the August 9 mission.
|Special Mission 16, Secondary target Nagasaki, August 9, 1945|
|Aircraft||Pilot||Call Sign||Mission role|
|Enola Gay||Captain George W. Marquardt||Dimples 82||Weather reconnaissance (Kokura)|
|Laggin’ Dragon||Captain Charles F. McKnight||Dimples 95||Weather reconnaissance (Nagasaki)|
|Bockscar||Major Charles W. Sweeney||Dimples 77||Weapon delivery|
|The Great Artiste||Captain Frederick C. Bock||Dimples 89||Blast measurement instrumentation|
|Big Stink||Major James I. Hopkins, Jr.||Dimples 90||Strike observation and photography|
|Full House||Major Ralph R. Taylor||Dimples 83||Strike spare – did not complete mission|
At 03:49 on the morning of August 9, 1945, Bockscar, flown by Sweeney’s crew, carried 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.
Last Minute Hitch
During pre-flight inspection of Bockscar, the flight engineer notified Sweeney that an inoperative fuel transfer pump made it impossible to use 640 US gallons (2,400 l; 530 imp gal) of fuel carried in a reserve tank. This fuel would still have to be carried all the way to Japan and back, consuming still more fuel. Replacing the pump would take hours; moving the Fat Man to another aircraft might take just as long and was dangerous as well, as the bomb was live. Tibbets and Sweeney therefore elected to have Bockscar continue the mission.
Serious RV Problems
This time Penney and Cheshire were allowed to accompany the mission, flying as observers on the third plane, Big Stink, flown by the group’s operations officer, Major James I. Hopkins, Jr. 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, Big Stink failed to make the rendezvous. According to Cheshire, Hopkins was at varying heights including 9,000 feet (2,700 m) higher than he should have been, and was not flying tight circles over Yakushima as previously agreed with Sweeney and Captain Frederick C. Bock, who was piloting the support B-29 The Great Artiste. Instead, Hopkins was flying 40-mile (64 km) dogleg patterns. Though ordered not to circle longer than fifteen minutes, Sweeney continued to wait for Big Stink for forty minutes. Before leaving the rendezvous point, Sweeney consulted Ashworth, who was in charge of the bomb. As commander of the aircraft, Sweeney made the decision to proceed to the primary, the city of Kokura.
Proceed to Kokura
After exceeding the original departure time limit by nearly a half-hour, Bockscar, accompanied by The Great Artiste, proceeded to Kokura, thirty minutes away. The delay at the rendezvous had resulted in clouds and drifting smoke over Kokura from fires started by a major firebombing raid by 224 B-29s on nearby Yahata the previous day. Additionally, the Yahata Steel Works intentionally burned coal tar, to produce black smoke. The clouds and smoke resulted in 70% of the area over Kokura being covered, obscuring the aiming point. Three bomb runs were made over the next 50 minutes, burning fuel and exposing the aircraft repeatedly to the heavy defenses around Kokura, but the bombardier was unable to drop visually. By the time of the third bomb run, Japanese anti-aircraft fire was getting close, and Second Lieutenant Jacob Beser, who was monitoring Japanese communications, reported activity on the Japanese fighter direction radio bands.
Low on Fuel – Head For Secondary Target Nagaski
With fuel running low because of the failed fuel pump, Bockscar and The Great Artiste 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, which had become entirely Allied-occupied territory only six weeks earlier. 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, Ashworth agreed with Sweeney’s suggestion 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 dropped instruments attached to three parachutes. These instruments also contained an unsigned letter to Professor Ryokichi Sagane, a 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 letter.
At 11:01, a last-minute break in the clouds over Nagasaki allowed Bockscar‘s bombardier, Captain Kermit Beahan, to visually sight the target as ordered. The Fat Man weapon, containing a core of about 5 kg (11 lb) of plutonium, was dropped over the city’s industrial valley. It exploded 47 seconds later at 1,650 ± 33 ft (503 ± 10 m), above a tennis court, halfway between the Mitsubishi Steel and Arms Works in the south and the Nagasaki Arsenal in the north. This was nearly 3 km (1.9 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 released the equivalent energy of 21 ± 2 kt (87.9 ± 8.4 TJ). Big Stink spotted the explosion from a hundred miles away, and flew over to observe.
Low Fuel Return to Base – By Bockscar
Bockscar flew on to Okinawa, arriving with only sufficient fuel for a single approach. Sweeney tried repeatedly to contact the control tower for landing clearance, but received no answer. He could see heavy air traffic landing and taking off from Yontan Airfield. Firing off every flare on board to alert the field to his emergency landing, the Bockscar came in fast, landing at 140 miles per hour (230 km/h) instead of the normal 120 miles per hour (190 km/h). The number two engine died from fuel starvation as he began the final approach. Touching down on only three engines midway down the landing strip, Bockscar bounced up into the air again for about 25 feet (7.6 m) before slamming back down hard. The heavy B-29 slewed left and towards a row of parked B-24 bombers before the pilots managed to regain control. Its reversible propellers were insufficient to slow the aircraft adequately, and with both pilots standing on the brakes, Bockscar made a swerving 90-degree turn at the end of the runway to avoid running off it. A second engine died from fuel exhaustion before the plane came to a stop.
Nagaski – Events on the ground
Although the bomb was more powerful than the one used on Hiroshima, its effects were confined by hillsides to the narrow Urakami Valley. Of 7,500 Japanese employees who worked inside the Mitsubishi Munitions plant, including “mobilized” students and regular workers, 6,200 were killed. Some 17,000–22,000 others who worked in other war plants and factories in the city died as well. Casualty estimates for immediate deaths vary widely, ranging from 22,000 to 75,000. At least 35,000–40,000 people were killed and 60,000 others injured. In the days and months following the explosion, more people died from their injuries. Estimates of total deaths by the end of 1945 ranged from 39,000 to 80,000.
The radius of total destruction was about 1 mi (1.6 km), followed by fires across the northern portion of the city to 2 mi (3.2 km) south of the bomb. About 58% of the Mitsubishi Arms Plant was damaged, and about 78% of the Mitsubishi Steel Works. The Mitsubishi Electric Works suffered only 10% structural damage as it was on the border of the main destruction zone. The Nagasaki Arsenal was destroyed in the blast. Although many fires likewise burnt following the bombing, in contrast to Hiroshima where sufficient fuel density was available, no firestorm developed in Nagasaki as the damaged areas did not furnish enough fuel to generate the phenomenon. Instead, the ambient wind at the time pushed the fire spread along the valley.
Preparations for More Atomic Attacks on Japan
Groves expected to have another “Fat Man” atomic bomb ready for use on August 19, with three more in September and a further three in October; a second Little Boy bomb (using U-235) would not be available until December 1945. On August 10, he sent a memorandum to Marshall in which he wrote that “the next bomb … should be ready for delivery on the first suitable weather after 17 or 18 August.” Marshall endorsed the memo with the hand-written comment, “It is not to be released over Japan without express authority from the President”, something Truman had requested that day. This modified the previous order that the target cities were to be attacked with atomic bombs “as made ready”. There was already discussion in the War Department about conserving the bombs then in production for Operation Downfall, and Marshall suggested to Stimson that the remaining cities on the target list be spared attack with atomic bombs. Two more Fat Man assemblies were readied, and scheduled to leave Kirtland Field for Tinian on August 11 and 14, and Tibbets was ordered by LeMay to return to Albuquerque, New Mexico, to collect them. At Los Alamos, technicians worked 24 hours straight to cast another plutonium core. Although cast, it still needed to be pressed and coated, which would take until August 16. Therefore, it could have been ready for use on August 19. Unable to reach Marshall, Groves ordered on his own authority on August 13 that the core should not be shipped.
Reluctant Surrender By Japan
Until August 9, Japan’s war council still insisted on its four conditions for surrender. The full cabinet met on 14:30 on August 9, and spent most of the day debating surrender. Anami conceded that victory was unlikely, but argued in favour of continuing the war nonetheless. The meeting ended at 17:30, with no decision having been reached. Suzuki went to the palace to report on the outcome of meeting, where he met with Kōichi Kido, the Lord Keeper of the Privy Seal of Japan. Kido informed him that the emperor had agreed to hold an imperial conference, and gave a strong indication that the emperor would consent to surrender on condition that kokutai be preserved. A second cabinet meeting was held at 18:00. Only four ministers supported Anami’s position of adhering to the four conditions, but since cabinet decisions had to be unanimous, no decision was reached before it ended at 22:00.
Japan Offers Conditional Surrender
Calling an imperial conference required the signatures of the prime minister and the two service chiefs, but the Chief Cabinet Secretary Hisatsune Sakomizu had already obtained signatures from Toyoda and General Yoshijirō Umezu in advance, and he reneged on his promise to inform them if a meeting was to be held. The meeting commenced at 23:50. No consensus had emerged by 02:00 on August 10, but the emperor gave his “sacred decision”, authorizing the Foreign Minister, Shigenori Tōgō, to notify the Allies that Japan would accept their terms on one condition, that the declaration “does not comprise any demand which prejudices the prerogatives of His Majesty as a Sovereign ruler.”
On August 12, the Emperor informed the imperial family of his decision to surrender. One of his uncles, Prince Asaka, then asked whether the war would be continued if the kokutai could not be preserved. Hirohito simply replied, “Of course.” As the Allied terms seemed to leave intact the principle of the preservation of the Throne, Hirohito recorded on August 14 his capitulation announcement which was broadcast to the Japanese nation the next day despite a short rebellion by militarists opposed to the surrender. In his declaration, Hirohito referred to the atomic bombings, and did not explicitly mention the Soviets as a factor for surrender.