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| The scene of destruction after the atomic bomb was dropped on Hiroshima, Japan, in 1945. Universal History Archive/Universal Images Group via Getty Images |
In May 1945, as World War II neared its conclusion, Germany surrendered to the Allied forces, but Japan refused to yield.
To bring the war to a swift end, President Harry Truman's administration made the decision to deploy an atomic bomb on the city of Hiroshima.
On August 6, 1945, the uranium-based atomic bomb known as "Little Boy" was dropped, instantly killing an estimated 80,000 people.
That morning, the 10-foot-long, 9,788-pound bomb detonated above Hiroshima, obliterating five square miles of the city and destroying more than 62,000 buildings.
The explosion's intensity was such that many victims were vaporized, leaving behind only eerie outlines known as “nuclear shadows.”
The attack remains one of the deadliest single days in Japan’s history and marked the dawn of the nuclear age. In the decades since, historians and scholars have debated the necessity and morality of the bombings as a means to end the war.
Eighty years later, here's a chronological account of why the US decided to drop the bomb, how the mission was carried out, and the devastating aftermath in Hiroshima.
1. On May 7, 1945, after nearly six years of war, Germany surrendered but Japan held out.
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| There were celebrations in New York on May 7, 1945, after Germany announced its surrender towards the end of World War II. Bettmann/Getty |
Germany's formal surrender ended the conflict in Europe. However, Japan, despite pressure from Allied nations including the US, Britain, China, and the Soviet Union, continued to fight and showed no signs of surrendering.
2. Meanwhile, Allied casualties were mounting rapidly.
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| A photo of the fallout after a kamikaze plane strike in May 1945 near Okinawa. MPI/Getty |
Between April and July 1945, Japan inflicted nearly half of the total Allied casualties it had caused throughout the previous three years, according to History.com.
3. President Truman took office in April and learned about the top-secret Manhattan Project.
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| President Harry Truman in 1945. MPI/Getty |
The new president was briefed on the project led by J. Robert Oppenheimer to develop atomic weapons. With Japan showing no willingness to surrender, Truman began to consider using this powerful new weapon.
Some military leaders proposed a full invasion of Japan, but projections warned it could lead to over 1 million American casualties.
Truman, unwilling to risk more US lives, leaned toward the atomic option, as reported by Al Jazeera.
Many commanders believed Japan was already on the verge of surrender and that atomic bombs were unnecessary.
Yet a committee led by Secretary of War Henry Stimson argued there was strong consensus in favor of deploying the bomb to force Japan’s hand.
4. A test detonation was successfully conducted on July 16 in New Mexico, and Truman soon issued a stern warning.
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| President Harry Truman with Soviet leader Josef Stalin and British Prime Minister Winston Churchill at the Potsdam Conference on July 17, 1945. AP Photo |
On July 26, Truman issued the Potsdam Declaration, demanding Japan’s unconditional surrender under threat of “prompt and utter destruction.”
Japan dismissed the ultimatum.
Intelligence reports revealed that Japan had prepared over 2.5 million troops and thousands of suicide planes for a potential US invasion. Plans were also uncovered to execute all US prisoners upon American arrival, according to the National WWII Museum.
5. Preparations for the bombing mission moved forward.
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| Enola Gay, the B-29 plane from which the first atom bomb was dropped, taken in April 1946. Art Edger/NY Daily News Archive/Getty |
A 12-man crew was assembled at a US airbase on the Pacific island of Tinian. Colonel Paul Tibbets was named the mission's pilot, with Captain Robert Lewis as co-pilot, according to The New York Times.
Captain William Parsons served as the weaponeer, and Second Lieutenant Morris Jeppson was the electronic test officer, according to the Atomic Heritage Foundation.
6. On August 5, the crew was briefed about their target: Hiroshima.
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A briefing held on August 5 led by Captain William Parsons and Colonel Paul Tibbets. PhotoQuest/Getty
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With a population of around 350,000 and a military base, Hiroshima was selected.
Tibbets informed his crew that they’d be bombing the city but did not initially tell them it would be an atomic bomb.
7. The bomb they were carrying was code-named "Little Boy."
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| A 1946 postwar replica of the "Little Boy" nuclear weapon dropped on Hiroshima, Japan, in August 1945. MPI/Getty Images |
It was a uranium-based weapon, 10 feet long and weighing nearly 10,000 pounds.
8. That same day, Little Boy was loaded into a B-29 bomber named "Enola Gay," after Tibbets’ mother.
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| Men around the Little Boy bomb the day before it was dropped in 1945. Bettmann/Getty |
The mission was officially confirmed for the following morning.
9. At 12:15 a.m. on August 6, the crew listened to a solemn prayer written for the occasion.
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| Colonel Paul Tibbets waved from his cockpit before takeoff from Tinian Island, on August 6, 1945. AP Photo |
At that point, they did not know whether they would survive the mission.
10. At 2:45 a.m., Enola Gay and two observation bombers took off from Tinian.
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| The Enola Gay in August 1945. Corbis/Getty |
Due to the weight of its cargo, the Enola Gay required the full two-mile runway.
Three additional weather planes were dispatched to scout conditions over potential target cities: Hiroshima, Kokura, and Nagasaki.
11. By 3 a.m., the bomb was being armed mid-flight.
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| Two men inspected Little Boy in August 1945. Universal History Archive/Universal Images Group/Getty |
Parsons and Jeppson began inserting the explosive components.
By 7:15 a.m., they had activated the arming devices, making Little Boy ready.
At 7:30 a.m., Tibbets announced to his crew, “We are carrying the world’s first atomic bomb.”
12. At 8:24 a.m., a weather report confirmed Hiroshima was a go.
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| A photo-diagram of Hiroshima issued by the US army on August 9, showing Hiroshima and the levels of damage caused by the atomic bomb. AP Photo |
Tibbets acknowledged the target, saying simply, “It’s Hiroshima.”
Their objective was the Aioi Bridge, described by Tibbets as “the most perfect aiming point I’ve seen in this whole damn war.”
13. At 8:15 a.m. local time, Little Boy was released from 31,060 feet above Hiroshima.
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| The atomic bomb explosion on Hiroshima in 1945. Roger Viollet/Getty Images |
It took 43 seconds to fall nearly six miles before detonating 1,900 feet above ground, according to the BBC.
Witnesses reported an intense white flash and then a massive mushroom cloud.
The fireball reached 900 feet in diameter, with an explosive force equal to 12,000 to 15,000 tons of TNT.
Tibbets immediately executed a 155-degree turn to escape.
By the time the bomb exploded, Enola Gay was already over 11 miles away.
14. The mushroom cloud rose nearly 2,500 feet into the sky.
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| An aerial view of Hiroshima on August 7, 1945. Hulton Archive/ Getty |
At the center of the fireball, temperatures soared to 300,000 degrees Celsius, while the surface heat reached around 7,000 degrees.
In his memoir, Tibbets later described the mushroom cloud as “boiling upward like something terribly alive,” The New York Times noted.
15. It became the most destructive bomb used in warfare at the time, flattening five square miles of the city.
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| Two victims of the atomic bombing sit in a converted hospital in October 1945. AP Photo |
Over 62,000 buildings were destroyed. Around 80,000 people died instantly.
Another 55,000 would perish by the end of 1945 from radiation and burn-related injuries.
According to the US Department of Energy, nearly 200,000 people had died within five years.
16. The intense heat vaporized some people, leaving only their "nuclear shadows."
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| Human shadow on bank steps, in Hiroshima after the explosion of the atom bomb in August 1945, Japan. Universal History Archive/Universal Image Group/Getty |
These eerie silhouettes were preserved outlines on surfaces shielded from the thermal blast, contrasting with areas bleached by the atomic heat, according to LiveScience.
17. Roof tiles melted together, and metal statues liquefied.
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| Hiroshima shown eight months after the atomic bomb was dropped. Galerie Bilderwelt/Getty |
Fires broke out across Hiroshima, spreading destruction even further.
18. After the bombing, the Enola Gay circled Hiroshima three times before heading back.
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| An aerial view of the mushroom cloud from the atomic bomb dropped on Hiroshima on August 6, 1945. US Army Air Corps/PhotoQuest/Getty |
It wasn't until the plane was 368 miles away that the crew lost sight of the towering mushroom cloud, per AHF.
19. At 2:58 p.m., the Enola Gay landed safely back at its base on Tinian. The round-trip mission lasted about 12 hours.
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| The Enola Gay lands back on Tinian after dropping an atomic bomb on Hiroshima. Bettmann/Getty |
Although the bombing did not end the war immediately, it ushered in a new era.
20. Hours later, President Truman delivered an ultimatum to Japan.
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| Survivors of the atomic bomb in hospital in 1945. Universal History Archive/Getty |
“If they do not accept our terms, they may expect a rain of ruin from the air the likes of which has never been seen on this Earth,” he said.
He vowed to destroy every above-ground Japanese industry if surrender was not forthcoming.
21. Three days later, the US dropped a second, more powerful bomb “Fat Man” on Nagasaki.
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| The explosion over Nagasaki in 1945. Prisma Bildagentur/Universal Images Group/Getty |
The blast killed approximately 70,000 people, including those who later died from radiation exposure, as reported by PBS.
22. On August 14, 1945, Japan surrendered, bringing World War II to a close.
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| Japanese prisoners of war in Guam bow their heads after hearing Emperor Hirohito's announcement of Japan's unconditional surrender. US Navy/Getty Images |
Emperor Hirohito announced the surrender in a recorded radio broadcast to the Japanese people.
Sources: AHF, National WWII Museum, BBC, History.com, Al Jazeera, LiveScience, The New York Times, PBS, and The History Press.
