Hiroshima explosion

The Hiroshima bomb was dropped on August 6, 1945, followed by the Nagasaki bomb on August 9. Six days later on August 15, 1945 the Japanese emperor announced in a radio broadcast that the war was over. Together the two bombs killed about 115,000 people instantly and an additional 95,000 within five months of the blasts .As of August 2014, the number of people recognized as having died from the effects of the two atomic bombs stood at more than 450,000: 292,325 in Hiroshima and 165,409 in Nagasaki,

The 15-kiloton Hiroshima nuclear bomb was dropped by a US B-29 bomber on the city on the morning of August 6. Between 60,000 and 80,000 people were killed instantly; in the months that followed the death toll rose to 140,000. One survivor said, “A lot of people died instantly... While trying to soothe burning skin, some died in the river when fireballs swept up the oil-slicked water. Others died years later, stricken by cancer.” Japanese were not the only ones who died. An estimated 40,000 to 50,000 Koreans killed by the atomic bombs dropped on Nagasaki and Hiroshima.

Describing the Nagasaki bomb, William T. Lawrence wrote of the New York Times on August 9, 1945: "It's a thing of beauty, this 'gadget.' Into its design went million of man-hours of what is without a doubt the most concentrated intellectual effort in history. Never before had so much brain power been focused on a single problem." [Source: “Eyewitness to History “, edited by John Carey, Avon Books, 1987]

United Nations Office of Disarmament Affairs (UNODA)

The Mushroom Club is a film by director Steven Okazaki about survivors of the bombing of Hiroshima and Nagasaki. It was nominated for an Academy Award in 2006 in the short documentary category. “White Light, Black Rain: The Destruction of Hiroshima and Nagasaki” is another documentary by Steven Okazaki. The film is very graphic. Some of the clips of bomb victims are difficult to look at.

Events Before Hiroshima

According to Columbia University’s Asia for Educators: “On April 1, 1945, the Allies invaded the southern Japanese island of Okinawa, and their victory there after bitter and bloody fighting with heavy losses on both sides proved that Japan could not win the war. It also proved, however, that invasion of the Japanese homeland would cause massive casualties on both sides. As American ground forces swept Okinawa clean of Japanese troops, the local civilians were caught in the middle. Subjected to gun fire, bombing, and infantry combat by the American advance, they were prevented from surrendering by the Japanese troops. Okinawa only served to confirm everyone's idea of how the final battle for the main islands of Japan would be fought. [Source: Asia for Educators Columbia University, Primary Sources with DBQs, ]

The surrender of Okinawa caused the Japanese cabinet to collapse and a new, pro-peace prime minister and foreign minister pressed the army to allow negotiations. The Japanese military, however, trapped in its own mystique of rigid determination and self-sacrifice in the name of the nation and emperor, insisted on strict terms.

Just at this point, the atomic bomb became a reality. The first successful test of the atomic weapon was held on July l6, 1945. The United States now had the choice of using it to try to end the war in another way. All other forms of attack, from the grim battle for Okinawa to the terrible fire bombing of Japan's cities, had failed to deter the leaders in Tôkyô. Perhaps the atomic bomb would resolve the crisis without a need for invasion. President Truman, who had already left for Potsdam to meet with Churchill and Stalin, left instructions that the bomb was not to be used against Japan until after the Allies had agreed on and issued a declaration.

Mission Map

The Potsdam Declaration of July 26, issued by the Allied powers and calling for "unconditional surrender," was not acceptable to the Japanese military, despite the declaration's threat that failure to surrender would be met by "complete destruction" of the military and the "utter devastation of the Japanese home land." Following ten days of Japanese silence, the atomic bomb was dropped on August 6, 1945, on the city of Hiroshima.

Hiroshima Bomb

On August 6, 1945, a 10½-foot-long atom bomb, code-named "Little Boy," was dropped on Hiroshima, a coastal city on Japan’s Inland Sea and the eighth largest city in Japan. Described by one crew member as "an elongated trash can with fins,” the 9,000-pound bomb was inscribed with nasty remarks about the Japanese Emperor. Of the 60 kilograms of uranium 235 used in the bomb about 1 kilogram was used for the detonation. Released from 31,600 feet, it exploded 1,890 feet above the ground with a force equal to 12,500 tons of TNT.

Joseph Kanon wrote in the Washington Post: “The detonation was a matter of nanoseconds. In one 10-millionth of a second, gamma rays escaped the core at light speed, followed by a spray of neutrons. Electrons were stripped from every atom of air and "a plasma bubble began to form, producing a thermal shock that spiked hotter than the Sun's core and glowed billions of times brighter than the surface." By the time it had slowed to biological time, 3/10 of a second later, the bomb itself was gone. People on the ground were vaporized, their bodies converted into gas and desiccated carbon. Some left thermal shadows, ghosts on bleached asphalt. Away from the hypocenter, death came minutes or hours later. Some died as "alligator people," skin burned crisp by the flash, some were ripped apart by the blast, still others sickened from radiation poisoning and bled out. A few, miraculously, survived, saved by shock cocoons or mere, capricious chance.” [Source: Joseph Kanon, Washington Post, February 7, 2010]

Up until that point Hiroshima had largely been spared from the fire-bombing raids that incinerated other Japanese cities. At 7:09am an air-raid alert had sounded when an Allied weather plane approached, followed by an all-clear signal at 7:31. When the Enola Gay, the plane carrying the bomb, approached no alarms sounded.

Little Boy was drooped from the Enola Gay at 8:15:30 and 43 seconds later, a radar antenna activated a conventional explosive that propelled a wedge of uranium-235 through a gun-barrel-like chamber into rings of uranium-235, setting off a self-sustaining nuclear chain reaction.

Choice of Hiroshima as a Target

Director of the Manhattan Project, Army General Leslie Grove, had originally wanted to drop an atomic bomb on the ancient capital of Kyoto, with it hundreds of shrines and temples, because he regarded it as the "intellectual center" of Japan and he wanted to bomb a place that "would most adversely affect the will of the Japanese people to continue the war." Secretary of War Henry Stimson, who had visited Kyoto in the 1920s, overruled Groves, arguing that destroying Japan's cultural capital was wrong. Niigata, another city that survived the firebombing raids, was another city on the shortlist of targets because it was still largely unscathed.

Hiroshima was by no means just a civilian target. It was Japan's western military capital and home of massive munitions factories and Japan's second largest military school.. There was a military headquarters in the middle of town; factories churned out large amounts of military hardware; and the Mitsubishi Heavy Industries shipyard was one of the major builders of giant warships. Hiroshima’s port on the Inland Sea was the staging area for military action in China, Korea and Southeast Asia. Before the atomic bomb was dropped Hiroshima had not been bombed at all. Some people have suggested that this was done on purpose to measure the destructive power of the bomb.

Hiroshima was home to around 250,000 people at the time the bomb was dropped. It was selected in part because it had a large industrial complex surrounded by densely populated residential areas and it was thought to have no prisoner-of-war camps. One advisor, suggested that the “the most desirable target would be a vital war plant employing a large number of workers and closely surrounded by worker’s houses.” Many of the people who worked in the factories were Chinese and Koreans forced to work in Japan.

Enola Gay

The “Enola Gay”, the plane that dropped the atomic bomb on Hiroshima, was a four-engine B-29 superfortress named after the mother of the commander of the plane (Lt. Col. Paul Tibbets Jr.). It took off at 2:45am from the tiny Pacific island of Tinian, which had been captured from the Japanese are year earlier, while more that 100 photographers, journalists and other people looked on, and reached Hiroshima in 6½ hours flying at a speed of 285 mph. Two other B-29s accompanied the Enola Gay. One carried scientific instruments; the other photographic equipment. The lumbering B-29 reached the target on time with no fighter escort and no resistance from Japanese fighters because the Japanese air force had been decimated by that point in the war.

The 12-man crew of the Enola Gay was aware of the awesome power of their payload. They carried cyanide capsules with them in case they were captured. Bombardier Tom Ferebe squeezed the trigger on his Norden bombsight that released the bomb, aiming at the T-shaped Aioi Bridge in the center of Hiroshima. Tibbets counted to 43 after the bomb was released and for a second thought the bomb was a dud before it exploded, producing a flash of light that temporarily blinded one crew member and generating a shock wave that caused the plane to lurch violently in the air.

After releasing the bomb Tibbets executed a well-rehearsed diving turn to avoid the effects of the blast. "A bright light filled the plane," Tibbets later wrote. "We turned back to look at Hiroshima. The city was hidden by the awful cloud...boiling up, mushrooming....As we turned for a heading that would take us alongside the burning, devastated city...the giant purple mushroom had already risen to a height of 45,000 feet, 3 miles above our own altitude, and was still boiling upwards like something terribly alive.” After the shock waves had subsided he told his crew, "Fellows, you have just dropped the first atomic bomb in history. I think we've won the war."

As the plane flew off Capt. Robert Lewis, the co-pilot exclaimed, "My God, what have we done?...Look at that son of a bitch go." Another crew member said the nuclear reaction produced a metallic taste in the air and said that Hiroshima looked "bubbling molasses...fires are springing up everywhere...its like a peep into hell." The Enola Gay had to travel 400 miles before the mushroom cloud was out of sight.

Tibbets died in November 2007 at the age of 92. He steadfastly defended his mission until the end. In an interview for the documentary “The Men Who Brought the Dawn” he said, “I was anxious to do it. I wanted to do everything I could to subdue Japan. I wanted to kill the bastards. That was the attitude of the United States in those years.” Referring to both American and Japanese casualties from an invasion of Japan, he said, “I have been convinced that we saved more lives than we took,” It could have been morally wrong if we’d have had the weapon and had not used it and let a million more people die.” The flight log used on the Enola Gay on the day of the bombing fetched $358, 500 at an auction.

Blinding Light, Fireballs and Intense Heat

The explosion of the atomic bomb at Hiroshima produced, in succession: a flash of light, scorching heat, a concussive shock wave, a firestorm, cyclonic winds and a twisting cloud that dropped radioactive black rain. At the moment of detonation the temperature at the center of the bomb exceeded 1 million degrees Celsius. The shock wave produced by the explosion was the equivalent of several hundred thousand atmospheres. The blast pressure 500 meters from ground zero was 19 tons per square inch, enough to send large buildings flying through the air.

The explosive produced a fireball that was remarkable small, only 110-meters in diameter, but for a split second temperatures at the center of the ball reached 300,000 degrees. The temperatures at ground zero directly below the explosion ranged between 5,400̊F and 7,200̊F. The surface of objects within a mile of ground zero rose to more than 1000̊F.

Survivor disagreed on the color of the light produced by the explosion. Some said it was yellow and blue; others described it as pink and red. Most described it as a blinding and white. The shock wave that followed blast surged forward at speed of two miles per second before slowing down to the speed of sound.

A German priest who was 4.5 kilometers north of ground zero said he spotted a B-29 in the clear sky as he was walking along reading a passage from the New Testament. While he watched the plane a huge, reddish-yellow fireball appeared that grew bigger and bigger beyond the nearest hill with tremendous speed. The flash of light, he said, was brighter than the sun and it reminded him of the Transfiguration. In the 14 seconds it took for the blast to reach him, he managed to make his way to the basement of a building, and positioned himself near a wall. He suffered only cuts as windows and window frames broke around him. Later he climbed a hill and saw the city engulfed in fire with a black dome-shaped cloud rising up and black rain started to fall.

Black Rain and Damage from the Hiroshima Bomb

After the explosion a 50,000-foot-high cloud of smoke turned the sky yellow and filled the air with "sickish, sweet, electric smell." Caused by the sudden appearance of over-heated air, the cloud rose into the stratosphere and briefly turned day into night. The tremendous heat and dust clashed with the chilly atmosphere, condensing water and forming sticky radioactive marble-size "black rain" that fell on Hiroshima and stained the skin of the survivors with red blotches.

One survivor recalled: "About half an hour after the explosion whilst the sky all around Hiroshima was cloudless a fine rain began to fall on the town and went on for about five minutes.....Then a violent wind rose and the fires extended with terrible rapidity, because most Japanese houses are built only of timber and straw."

The Hiroshima bomb flattened 3.9 square miles of the city. Of Hiroshima's 76,000 buildings, only 6,000 were undamaged and 48,000 were destroyed completely. Within a 1,000-meter radius of ground zero granite buildings melted, roof tiles boiled, birds ignited in mid-air, potatoes cooked in the ground, wood and paper homes ignited, stones glowed, steel bridges burned, and people vaporized and left "shadows' on the buildings and walls. Fire raced through the city, pushed forward by bomb-generated whirlwinds.

The bomb exploded over Shima Surgical Hospital, about 185 yards from its intended target the Aioi Bridge. Ground zero was near the Motoyasu River in the center of the city. On one side of the river is the burnt-out skeletal dome of the Industrial Exposition Hall (A-Bomb Dome), the only building near Ground Zero whose framework survived the explosion.

In some respects the damage in Hiroshima wasn’t that much worse than what had been inflicted by conventional bombs in other cities. Of the 68 cities bombed in 1945, Hiroshima was second in terms of people killed, forth in terms of square kilometers destroyed and 17th in terms of percentage of the city destroyed. The Japanese War Minister said after the war the atomic bombing of Hiroshima was no worse than the firebombing other cities suffered though earlier in the summer.

Casualties of the Hiroshima Bomb

Around 420,000 people lived in Hiroshima at the beginning of World War II. At the time of the blast about 280,000 civilians, 43,000 military personal and 20,000 forced Korean laborers and volunteer workers lived there. At the end of 1945 only 140,000 people lived there.

About 80,000 people in Hiroshima were killed instantly by the atomic bomb and an additional 60,000 died within five months of leukemia, radiation sickness and burns. Sixty-five of Hiroshima's 150 doctors died in the blast and 90 percent of the nurses were either dead or unable to work. Robert Oppenheimer had estimated that only 20,000 would die from the bomb.

About 1,000 to 1,500 feet from the hypocenter 544 middle school students at the Hiroshima Municipal Girls' High School were clearing rubble to make a firebreak. "Most died instantly. A few apparently survived the initial explosion only to die in the flames that followed. Sixteen of the 544 girl survived. Many funeral urns at the Buddhist temples that honor the dead are filled with rocks because no remains were ever found.

An estimated 3,000 U.S. citizens died at Hiroshima. Most were Nisei (second generation) U.S. citizens of Japanese descent who were in Japan when the war broke out. Of the 25 Allied prisoners of war in Hiroshima at the time of blast, only five survived. One American soldier that survived the blast that was pulled from the ruins of a detention center and butchered by a mob of angry Japanese. Two others were also killed by angry Japanese only a few hours after the blast. The other two died of radiation poisoning 11 day later.

After the bombing a captured B-29 crew was taken to Hiroshima. Before they were executed, a Japanese military police captain shouted at them, "Look what you have done. One bomb! One bomb! Look there. The blue light is women burning. It is babies burning. Is it wonderful to see the babies burning?"

Announcements of the Hiroshima Explosion and American Reaction to It

The world learned of the atomic blast at Hiroshima from a White House statement that didn't get to the point until the third paragraph. "It is an atomic bomb," it read. “It is a harnessing of the basic power of the universe. The force from which the sun draws its powers has been loosed against the those who brought war to the Far East." After returning from Potsdam on August 7, Truman told the American people, “We have spent $2 billion on the greatest scientific gamble in history and won.” Later when Truman was asked by reporters on television if he lost any sleep over his decision, he started straight at the camera and said: “A bunch of cry babies.”

Japanese radio released a report saying, "Hiroshima suffered considerable damage as the result of an attack by a few B-29s. Our enemies have apparently used a new type of bomb. The details are being investigated." For days after the explosion, Tokyo knew little about what had actually happened. General George Marshall later said, "What we did not take into consideration was that the destruction would be so complete that it would be an appreciable time before the actual facts of the case would get to Tokyo."

In the U.S. Things were different. "THANK GOD FOR THE ATOMIC BOMB" screamed a headline of the New Republic. Upon hearing news of the destruction of Hiroshima, one American soldier wrote: "We whooped and yelled like mad, we downed all the beer we'd been stashing away. We shot bullets in the air and danced between the tent rows."

Paul Fussell, a 21-year-old lieutenant in a rifle platoon later told Newsweek, "for all fake manliness of our facades, we cried with relief and joy. We were going to live. We are going to grow up to adulthood after all." "My ship erupted with whoops and shouts of joy," wrote ensign Osborn Eliiot, later editor-in-chief of Newsweek. "A few days earlier we had been bombarding the Japanese mainland, and the war seemed a long way from being over. But now all that had changed.

Nagasaki Bombing


On August 9th, 1945 the 10,000-pound Fat Man plutonium bomb was dropped on Nagasaki at 11:02am. It exploded 1,650 feet above the ground, producing a blast almost twice as powerful as the Hiroshima bomb (the equivalent of 22,000 tons of TNT). Named after Winston Churchill, a Fat Man bomb was exploded in the first nuclear test on July 16, 1945. A third was waiting to be used if necessary.

The Nagasaki bomb was dropped from a B-29 flown by Maj. Charles Sweeney. It exploded over the largest Roman Catholic cathedral in the Far East. Nagasaki’s steep hills limited the damage primarily to the Urakami valley. About 35,000 people were killed instantly and another 35,000 died over the next few months. The victims included 250 Allied prisoners of war. One survivor from Nagasaki said, "My body seemed all black; everything seemed dark...I thought, 'The world is ending.'" There were reports of blackened horses standing in instant death.

Unlike Hiroshima, which had major military installations and little of historical value, Nagasaki had few military targets but many old Christian-European monuments. Many parts of the city were spared because they were shielded from the blast by mountains and hills.

Nagasaki was originally the secondary target and the only reason it was bombed was that the primary target was covered in clouds. The plane flew over the main target, Kokura (present-day Kitakyushu) three times without finding a target before take off for Nagasaki, which was not far away. Nagasaki was also covered by clouds but a gap opened up and the Mitsubishi Arms Work was sighted and became the target. After the bomb was dropped the plane flew to Okinawa, its tanks almost empty of fuel.

Riding in plane behind the plane carrying the Nagasaki bomb, William T. Lawrence wrote of the New York Times on August 9, 1945: "The winds of destiny seemed to favor certain Japanese cities...We circled about them again and again and found no opening in the thick umbrella of clouds that covered them. Destiny chose Nagasaki as the ultimate target." [Source: “Eyewitness to History “, edited by John Carey, Avon Books, 1987]

Account from an American Plane of Nagasaki

The plane that carried the Nagasaki bomb was a B-29 bomber called Bock's Car. It took off from Tinian. "We heard the prearranged signal on our radio, put on our arc-welders glasses and watched tensely," Lawrence wrote in New York Times. "Out of the belly of The Great Ariste what looked like a black object went downward...Even though we were away in the opposite direction, and despite the fact that it was broad daylight in our cabin, all of us became aware of a giant flash that broke through the dark barrier of our arc-welders' lenses and flooded our cabin with light." [Source: “Eyewitness to History “, edited by John Carey, Avon Books, 1987]

"We removed our glasses after the first flash, but the light still lingered on, a bluish greenish light that illuminated the entire sky all around. A tremendous blast wave struck our ship and it trembled nose to tail. This was followed by four more blasts in repaid succession, each resounding like the boom of a cannon fire hitting our plane from all directions.

Observers from the back our plane saw a giant ball of fire rise as though from the bowels of the earth, belching forth enormous white smoke rings. Next they saw a giant pillar of purple fire, 10,000 feet high, shooting skywards with enormous speed...By the time our ship made another turn in the direction of the atomic explosion the pillar of purple fire had reached the level of our altitude. Only about 45 seconds had appeared. Awe-struck we watched it shoot upwards like a meteor coming from the earth instead of from outer space, becoming even more alive as it climbed skyward through the white clouds."

"Then, just when it appeared as though the thing had settled down into a state of permanence, there came shooting out of the top a giant mushroom that increased the height of the pillar to a total of 45,000 feet. The mushroom top was even more alive than the pillar, seething and boiling in a white furry of creamy foam, sizzling upward and then descending earthward, a thousand Old Faithful geysers rolled into one."


Impact of the Atomic Bombing on Japan

According to Columbia University’s Asia for Educators: The day after the Hiroshima bombing it was reported to the Japanese Army General Staff that "the whole city of Hiroshima was destroyed instantly by a single bomb." On August 8 the army was further rocked by the news that the Russians, who had remained neutral to Japan throughout the war, had attacked Japanese forces on the Asian mainland. But despite the prime minister's insistence that Japan must accept surrender, the army insisted on total, last-ditch resistance. The news, midway through this conference, that the city of Nagasaki had also been destroyed by another atomic bomb, did not sway them from their determination. Finally, the Japanese prime minister and his allies agreed that the only course was to have the emperor break the deadlock by expressing his view. The emperor's statement that Japan's suffering was unbearable to him and that he wished for surrender broke the military's opposition and began the process of ending the war in the Pacific.” [Source: Asia for Educators Columbia University, Primary Sources with DBQs, ]

Image Sources: National Archives of the United States; Wikimedia Commons; Gensuikan;

Text Sources: National Geographic, Smithsonian magazine, New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, Yomiuri Shimbun, The New Yorker, Lonely Planet Guides, Time, Newsweek, Reuters, AP, AFP, Wikipedia, BBC, “Eyewitness to History “, edited by John Carey ( Avon Books, 1987), Compton’s Encyclopedia, “History of Warfare “ by John Keegan, Vintage Books, Eyewitness to, “The Good War An Oral History of World War II” by Studs Terkel, Hamish Hamilton, 1985, BBC’s People’s War website and various books and other publications.

Last updated November 2016

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