Atomic bombings of Hiroshima and Nagasaki

• 1. Introduction

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  The atomic bombings of Hiroshima and Nagasaki killed between 150,000 and 246,000 people, most of them civilians. On the 6th of August 1945, the United States dropped a bomb on Hiroshima. Three days later, on the 9th of August, a second bomb fell on Nagasaki. These remain the first and only uses of nuclear weapons in an armed conflict. Roughly half the deaths occurred on the first day in each city. The rest came over weeks and months, from burns, radiation sickness, illness, and malnutrition.

  In the final year of World War II, the Allies were preparing to invade the Japanese mainland. They expected it to be costly. A conventional bombing and firebombing campaign had already devastated 64 Japanese cities. Germany had surrendered on the 8th of May 1945, freeing the Allies to turn their full attention to the Pacific. How did the choice fall on these two cities? Who decided which targets would burn, and which would be spared? And why, decades later, are scholars still arguing over whether any of it was necessary? Japan announced its surrender on the 15th of August, six days after Nagasaki and the Soviet declaration of war.

• 2. The Race For The Bomb

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  The discovery of nuclear fission in 1938 turned an atomic bomb from fantasy into a theoretical possibility. Scientists who had fled Nazi Germany and other fascist countries feared a German project would build such a weapon first. That fear reached President Roosevelt through the Einstein-Szilard letter in 1939, prompting preliminary American research late that year. Progress was slow at first.

  The British MAUD Committee report, arriving in late 1941, changed the math. It indicated that only 5 to 10 kilograms of isotopically pure uranium-235 were needed for a bomb, rather than tons of natural uranium and a neutron moderator like heavy water. Work accelerated. Roosevelt agreed to hand the effort to the U.S. Army Corps of Engineers to build the facilities for producing uranium-235 and plutonium-239. The work was consolidated into the Manhattan Engineer District, better known as the Manhattan Project, under Major General Leslie R. Groves, Jr.

  The project sprawled across dozens of sites in the United States and even some beyond its borders. It cost over two billion dollars and at its peak employed more than 125,000 people at once. Groves appointed J. Robert Oppenheimer to head the Los Alamos Laboratory in New Mexico, where bomb design took place. Two designs emerged. Little Boy was a gun-type fission weapon using uranium-235. Fat Man was a more complex implosion-type weapon using plutonium-239. Japan had a nuclear program of its own, but it lacked the human, mineral, and financial resources of the Manhattan Project and never made much progress.

• 3. A War Measured In Casualties

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  By 1945 the Pacific War had entered its fourth year, and most Japanese units fought to the death. The United States suffered 1.25 million battle casualties across the whole of World War II, and nearly a million of those came in the war's last year, from June 1944 to June 1945. American manpower reserves were running low. Deferments for groups such as agricultural workers were tightened, and drafting women was even considered. The public was war-weary and wanted long-serving men sent home.

  Nearly 99 percent of the 21,000 defenders of Iwo Jima were killed. Of the 117,000 Okinawan and Japanese troops on Okinawa from April to June 1945-94 percent died. The 7,401 Japanese soldiers who surrendered there were an unprecedentedly large number. Along the way, the ratio of Japanese to American casualties fell from five to one in the Philippines to two to one on Okinawa.

  Japan's merchant fleet shrank from 5,250,000 gross register tons in 1941 to 557,000 tons by August 1945. The 1945 fishing catch was only 22 percent of the 1941 figure, and the rice harvest was the worst since 1909. Hunger and malnutrition spread. American industrial power dwarfed Japan's. By 1943 the United States built nearly 100,000 aircraft a year, against Japan's 70,000 for the entire war. In February 1945, Prince Fumimaro Konoe told Emperor Hirohito that defeat was inevitable and urged him to abdicate.

• 4. Operation Downfall

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  Operation Downfall was the planned Allied invasion of Japan, and it would have been the largest operation of the Pacific War. It came in two parts. Operation Olympic, set for October 1945, called for the U.S. Sixth Army to land and capture the southern third of Kyushu. Operation Coronet would follow in March 1946, taking the Kanto Plain near Tokyo on Honshu with the U.S. First, Eighth, and Tenth Armies plus a Commonwealth Corps of Australian, British, and Canadian divisions.

  Japan's geography made the plan obvious, and the Japanese predicted it accurately, adjusting their own defensive plan, Operation Ketsugo. They prepared an all-out defense of Kyushu with little held in reserve. In all, 2.3 million Japanese Army troops stood ready to defend the home islands, backed by a civilian militia of 28 million. Vice Admiral Takijiro Onishi predicted up to 20 million Japanese deaths.

  Casualty predictions varied wildly. A Joint War Plans Committee study on the 15th of June 1945 estimated Downfall would cause 132,500 to 220,000 U.S. casualties, with 27,500 to 50,000 dead and missing. A separate study commissioned by Secretary of War Henry L. Stimson, by Quincy Wright and William Shockley, estimated between 1.7 and 4 million Allied casualties and Japanese deaths of around 5 to 10 million. General George C. Marshall even contemplated using poison gas, and quantities of phosgene, mustard gas, tear gas, and cyanogen chloride were moved to Luzon. Consideration was also given to biological weapons.

• 5. Burning The Paper Cities

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  The firebombing of Tokyo, codenamed Operation Meetinghouse, killed an estimated 100,000 people in a single night on the 9th to the 10th of March. It destroyed 16 square miles of the city and 267,000 buildings, at a cost of 20 B-29s shot down. It was the deadliest bombing raid of the war. This was the work of the long-ranged Boeing B-29 Superfortress, which only became ready for combat in mid-1944.

  An early effort, Operation Matterhorn, sent India-based B-29s through bases near Chengdu in China to strike Japan, but logistics, mechanical trouble, and extreme range made it fail. The campaign found firmer ground in the Mariana Islands. Guam, Tinian, and Saipan were captured between June and August 1944, and B-29 operations began from there in October. The XXI Bomber Command flew its first mission against Japan on the 18th of November 1944.

  Major General Curtis LeMay took command in January 1945. High-altitude precision bombing kept failing, partly because much Japanese manufacturing happened in small workshops and private homes. LeMay switched to low-level incendiary raids against cities. Over six months his command firebombed 64 Japanese cities. By May, 75 percent of bombs dropped were incendiaries meant to burn down Japan's paper cities. By mid-June, Japan's six largest cities had been devastated. Japanese fighters and anti-aircraft guns struggled to reach bombers at high altitude, and from April 1945 they also faced American fighter escorts from Iwo Jima and Okinawa.

• 6. The 509th Composite Group

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  Colonel Paul Tibbets was assigned to build a unit that could deliver an atomic weapon against targets in Germany and Japan. The 509th Composite Group was constituted on the 9th of December 1944 and activated days later at Wendover Army Air Field, Utah. Because its squadrons mixed bomber and transport aircraft, it was called a composite rather than a bombardment unit. Tibbets chose Wendover for its remoteness over Great Bend, Kansas and Mountain Home, Idaho.

  Each bombardier completed at least 50 practice drops of inert or conventional pumpkin bombs, targeting islands around Tinian and later the Japanese home islands, some as late as the 14th of August 1945. Some missions over Japan were flown by single unescorted bombers carrying a single payload, deliberately accustoming the Japanese to that pattern. Tibbets himself was barred from most missions over Japan, for fear he might be captured and interrogated.

  The 509th had an authorized strength of 225 officers and 1,542 enlisted men. Attached to it on Tinian were 51 personnel from Project Alberta, known as the 1st Technical Detachment. The 393rd Bombardment Squadron was equipped with 15 Silverplate B-29s, specially adapted with fuel-injected engines, reversible-pitch propellers, and pneumatic actuators for rapid bomb bay doors. The ground echelon sailed from Seattle on the SS Cape Victory on the 6th of May 1945. On Tinian, Brigadier General Thomas Farrell, Rear Admiral William R. Purnell, and Captain William S. Parsons became known as the Tinian Joint Chiefs.

• 7. Choosing The Targets

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  The Target Committee, chaired by Groves, met first in Washington on the 27th of April, then at Los Alamos on the 10th of May, then in Washington again on the 28th of May. Its members included scientists John von Neumann, Robert R. Wilson, and William Penney. They nominated five targets: Kokura, site of one of Japan's largest munitions plants; Hiroshima, an embarkation port and industrial center with a major military headquarters; Yokohama; Niigata; and Kyoto. A target had to be larger than three miles across, capable of effective blast damage, and unlikely to be attacked by August 1945.

  These cities were largely spared the nightly raids so the atomic damage could be measured cleanly. The committee wrote that psychological factors were of great importance, both for the effect on Japan and for making the first use spectacular enough to be internationally recognized. Hiroshima, it noted, had nearby mountains that might focus and increase the blast.

  Kyoto's fate turned on one man. Stimson, who admired the city, asked Groves on the 30th of May to remove it for its historical, religious, and cultural significance. Groves pointed to its military and industrial value, so Stimson took the matter to President Harry S. Truman, who agreed. Groves tried to restore Kyoto in July, but Stimson held firm. On the 25th of July, Nagasaki was placed on the list in its stead, a major military port and one of Japan's largest shipbuilding centers. In his diary that day, Truman wrote that the target would be a purely military one, and that he had told Stimson to spare women and children and the old capital.

• 8. Demonstration Or Surprise

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  Scientist Ernest Lawrence suggested a non-combat demonstration during meetings on the 31st of May and the 1st of June. The idea was to show the Japanese the bomb's power without dropping it on a city. Arthur Compton later recalled why the idea was rejected. An atomic bomb was an intricate device still in the developmental stage. If it failed during an advertised demonstration, the result would be worse than not trying at all. At the start of August only one bomb would be available, with others to follow at long intervals, so no one could risk a dud.

  The possibility returned in the Franck Report, issued by physicist James Franck on the 11th of June. The Scientific Advisory Panel rejected it on the 16th of June, saying it could propose no technical demonstration likely to end the war and saw no acceptable alternative to direct military use. The Interim Committee met again on the 21st of June and reaffirmed that conclusion.

  There were further worries. Allied prisoners of war might be moved to a demonstration site and killed. The bomb might fail, since the Trinity test had used a stationary device rather than an air-dropped one. The Oppenheimer-led Scientific Panel ultimately decided against both a demonstration bomb and a special leaflet warning for Hiroshima, citing the uncertainty of detonation and the wish to maximize shock in the leadership. No warning was given to Hiroshima that a new and far more destructive bomb was coming.

  The Quebec Agreement of 1943 required that nuclear weapons not be used against another country without mutual consent, so Stimson had to obtain British permission. The Combined Policy Committee met at the Pentagon on the 4th of July 1945. Field Marshal Sir Henry Maitland Wilson announced that the British government concurred with using nuclear weapons against Japan. The meeting also weighed what scientific details could be revealed in the press, and what Truman could tell Joseph Stalin at the upcoming Potsdam Conference.

  The Trinity Test in the New Mexico desert succeeded on the 16th of July, exceeding expectations. On the 26th of July, Allied leaders issued the Potsdam Declaration, an ultimatum outlining surrender terms and threatening the utter devastation of the Japanese homeland. The atomic bomb was not mentioned. The alternative to surrender was described as prompt and utter destruction.

  On the 28th of July, Prime Minister Kantaro Suzuki told a press conference that the declaration was no more than a rehash of the Cairo Declaration, using the word mokusatsu, to kill by silence. Both Japanese and foreign papers took this as a clear rejection. Japan's willingness to surrender remained conditional on preserving the kokutai, the Imperial institution and national polity. Orders for the attack were issued to General Carl Spaatz on the 25th of July under the signature of General Thomas T. Handy, the acting chief of staff, since Marshall was at Potsdam. The order named Hiroshima, Kokura, Niigata, and Nagasaki, with the first bomb to be delivered as soon as weather permitted visual bombing after about the 3rd of August.

  At 02:45 local time on the 6th of August, the B-29 Enola Gay took off from North Field on Tinian, about six hours from Japan. Tibbets had named the aircraft after his mother and piloted it himself. Two other B-29s came along: The Great Artiste, commanded by Major Charles Sweeney, carrying instrumentation, and a then-nameless aircraft later called Necessary Evil, the photography plane. Parsons armed the bomb in flight to reduce the risk during takeoff, having watched four B-29s crash and burn on takeoff. His assistant, Second Lieutenant Morris R. Jeppson, removed the safety devices 30 minutes before the target.

  The city had an all-clear at 07:31, and many people were outdoors. At 08:09 Tibbets began his bomb run and handed control to his bombardier, Major Thomas Ferebee. The release came at 08:15 Hiroshima time. The Little Boy, holding about 64 kilograms of uranium-235, fell for 44.4 seconds from about 31,000 feet to a detonation height of around 1,900 feet. A crosswind carried it about 800 feet from the aiming point, the Aioi Bridge, and it burst directly over the Shima Surgical Clinic.

  The weapon released energy equivalent to 16 kilotons of TNT, four times the tonnage of conventional bombs that had destroyed Dresden. It was very inefficient, with only 1.7 percent of its material fissioning. The radius of total destruction was about a mile, with fires across 4.4 square miles. Enola Gay was about 11.5 miles away when the shock waves reached it. Only Tibbets, Parsons, and Ferebee knew the weapon's true nature. When Tibbets stepped from the aircraft on Tinian, the Distinguished Service Cross was pinned to his chest while he still held his pipe.

  Survivors on the ground reported a brilliant flash of light followed by a loud booming sound. A common thread in their accounts was the sense that an ordinary weapon had gone off right beside them, throwing people across rooms and crushing buildings. Only later, emerging from the ruins, did they grasp that the whole city had been struck in the same instant. People walked through the wreckage without a clear sense of where to go, hearing the cries of those trapped in collapsed structures. Many jumped into Hiroshima's rivers seeking refuge from the firestorm, and many of them drowned.

  The photographer Yoshito Matsushige took the only photographs of Hiroshima immediately after the bombing, just five before he could not continue. He said it was like something out of hell. Some survivors looked uninjured yet died within hours or days from what was later identified as radiation sickness. Over 90 percent of the doctors and 93 percent of the nurses in the city were killed or injured. Only one doctor, Terufumi Sasaki, remained on duty at the Red Cross Hospital.

  Eizo Nomura was the closest known survivor, in the basement of a reinforced concrete building only 170 meters from ground zero; he died in 1982, aged 84. Akiko Takakura survived inside the Bank of Hiroshima, only 300 meters from ground zero. The bomb killed 3,243 troops doing physical training on the grounds of Hiroshima Castle. Mayor Senkichi Awaya was killed, so Field Marshal Shunroku Hata, only slightly wounded, took over the city's administration. One to two hours after the blast, a black rain fell, a tarry mix of ash, radioactive fallout, and water that caused severe radiation burns. The Prefectural Industrial Promotional Hall, only 150 meters from the hypocenter, survived and is now the Genbaku dome, made a UNESCO World Heritage Site in 1996.

  The Japan Broadcasting Corporation's Tokyo control operator noticed that the Hiroshima station had gone off the air. He tried another telephone line, and it too had failed. About 20 minutes later, the Tokyo railroad telegraph center realized the main line had stopped just north of Hiroshima. Small railway stops within sixteen kilometers sent confused reports of a terrible explosion. The Imperial Japanese Army General Staff was puzzled by the complete silence, knowing no large raid had occurred and no sizable store of explosives sat in the city.

  A young staff officer was ordered to fly to Hiroshima, land, survey the damage, and return. Many on the staff felt nothing serious had happened and the explosion was just a rumor. After flying for about three hours, while still nearly 160 kilometers away, he and his pilot saw a great cloud of smoke from the firestorm. They circled, landed south of the city, and the officer began to organize relief.

  The first report from Hiroshima was sent by Yoshie Okawa, a fourteen-year-old female student volunteer communications officer, from a bunker at the Chugoku Military District Headquarters about half a mile from the epicenter. She was not believed at Fukuyama. So she found a soldier above ground, who told her that Hiroshima had been attacked by a new type of bomb and the city was in a state of near-total destruction. Tokyo learned the full truth from President Truman's announcement of the strike, sixteen hours later.

  Sixteen hours after Hiroshima, a statement issued in Truman's name said the United States and its allies had spent two billion dollars on the greatest scientific gamble in history, and won. It warned Japan to expect a rain of ruin from the air the like of which had never been seen on this earth. A 50,000-watt station on Saipan broadcast a similar message to Japan every 15 minutes, urging civilians to evacuate major cities.

  The Soviet Union had already abrogated the Soviet-Japanese Neutrality Pact. At two minutes past midnight on the 9th of August, Tokyo time, Soviet infantry, armor, and air forces launched the Manchurian Strategic Offensive Operation. Four hours later, word of the Soviet declaration of war reached Tokyo. The senior Japanese Army leadership began preparing to impose martial law, with the support of Minister of War Korechika Anami, to stop anyone seeking peace.

  On the 7th of August, the atomic physicist Yoshio Nishina and others reached Hiroshima, examined the damage, and told the cabinet that a nuclear weapon had indeed destroyed the city. Admiral Soemu Toyoda, Chief of the Naval General Staff, estimated that no more than one or two further bombs could be readied, so the leadership decided to endure the remaining attacks. American Magic codebreakers intercepted the cabinet's messages. Purnell, Parsons, Tibbets, Spaatz, and LeMay met on Guam to decide what came next. With no sign of surrender, they chose to drop another bomb, and Tibbets asked whether it could be ready by the 9th of August rather than the 11th.

  Nagasaki had been one of the largest seaports in southern Japan, vital for its wide-ranging industry, including ordnance, ships, and military equipment. Its four largest companies, the Mitsubishi Shipyards, Electrical Shipyards, Arms Plant, and Steel and Arms Works, employed about 90 percent of the city's labor force. The city had largely been spared firebombing because its geography made it hard to find at night by radar. It had been bombed on a small scale five times, including a conventional raid on the 1st of August. On the day of the atomic bombing, an estimated 263,000 people were in Nagasaki, among them 10,000 Korean residents, 2,500 conscripted Korean workers, 600 conscripted Chinese workers, and 400 Allied prisoners of war.

  According to one crew member, Hiroshima had been the perfect mission where everything went right, whereas on the Nagasaki mission almost everything would go wrong. The raid was moved earlier by two days to avoid a forecast spell of bad weather. At 02:47 Japanese time on the 9th of August, Bockscar, flown by Sweeney's crew, lifted off from Tinian with the Fat Man. Kokura was the primary target and Nagasaki the secondary. An inoperative fuel transfer pump left 640 US gallons of reserve fuel unusable, yet Tibbets and Sweeney chose to fly the mission anyway. This time Penney and Cheshire were allowed along as observers, on the third plane, Big Stink.

  Big Stink failed to make the rendezvous off the coast of Japan. According to Cheshire, its pilot, Major James I. Hopkins, Jr., flew at varying heights and in 40-mile dogleg patterns instead of tight circles over Yakushima. Though ordered not to circle longer than fifteen minutes, Sweeney waited forty. By the time Bockscar reached Kokura, drifting smoke from a firebombing raid by 224 B-29s on nearby Yahata the day before, plus coal tar deliberately burned at the Yahata Steel Works, covered 70 percent of the area. Three bomb runs over fifty minutes failed to find the aiming point visually, while Japanese anti-aircraft fire crept closer and Second Lieutenant Jacob Beser reported activity on the fighter direction radio bands.