Visualising Hiroshima and Nagasaki casualties, the world’s first atomic attacks

Eighty years ago, on August 6 and 9 in 1945, the Japanese cities of Hiroshima and Nagasaki experienced the destructive force of the world’s first atomic bomb attacks. Two American bombs caused the deaths of tens of thousands and unleashed widespread devastation. These events occurred in the final throes of World War II, following a long and brutal campaign by Japan in China and across Asia that resulted in millions of civilian deaths, injuries, and widespread atrocities. In Hong Kong alone, at least 10,000 civilians were killed.
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The US decision to bomb Japan twice was made against a backdrop of a Japanese military government that, despite the war’s clear conclusion, was determined to keep fighting. This refusal to accept an unconditional surrender was a key factor in the US strategy to force a swift end to the conflict and avoid a costly ground invasion. In the wake of the two bombings, Japan’s Emperor Hirohito announced his nation’s surrender on August 15, 1945, ending the Pacific War. This came after Germany had surrendered in Europe on May 7.

This infographic utilises the symbolic origami crane , a Japanese symbol associated with peace and remembrance, to depict the human cost of the atomic bombings.

Each stamp features 100 crane silhouettes, with each silhouette representing one casualty.

Hiroshima August 6, 1945 8.15am

The US B-29 bomber Enola Gay dropped a uranium-based bomb nicknamed “Little Boy” over Hiroshima. This was the first atomic bomb ever used against a civilian target.

The city's population was approximately 350,000.

Within a 1.2km radius of the hypocenter, an estimated 70,000 people were killed or missing and presumed dead on that day.

Hiroshima’s prefectural health department estimated causes of death at:

Nagasaki August 9, 1945 11.02am

Three days after Hiroshima, the US B-29 bomber Bockscar dropped a plutonium bomb dubbed “Fat Man” over Nagasaki, a city of 240,000 people.

An estimated 40,000 people were killed instantly.

Throughout the rest of 1945 and subsequent years, casualties continued to mount, with radiation exposure leading to widespread cancer cases and chronic diseases among survivors.

Approximately 93% of doctors and nurses (1,834) were killed in the explosion.

Only three out of 45 civilian hospitals remained operational, critically limiting first-aid and rescue efforts in the immediate hours. This lack of medical infrastructure exacerbated casualties.

Over 80% of Nagasaki's hospital capacity was destroyed.

At the Nagasaki Medical College (0.6km from the hypocenter), almost 30% of medical staff and 600 out of 850 medical students perished.

An estimated 7,200 students , mobilised for wartime demolition work, were killed in Hiroshima.

About 200 Hiroshima railroad employees also died.

112 out of 115 streetcar company employees also died; no streetcars operated in Nagasaki until mid-November 1945.

In total, more than 38,000 children died in both cities.

During World War II, many Korean nationals in Japan were subjected to forced labour. While the exact figures remain unknown for those killed in the atomic attacks: An estimated 20,000 died in Hiroshima. An estimated 10,000 died in Nagasaki.

By the end of 1945, nearly 140,000 people had died in Hiroshima. And around 74,000 people had died in Nagasaki.

The precise number of atomic bombing casualties in both cities remains impossible to ascertain.

This is due to the massive destruction of civilian infrastructure and immediate post-explosion confusion. Japanese censuses before 1945 were not considered complete.

In destroyed buildings, bodies were burned beyond recognition.

Corpses and body parts were disposed of through mass cremations during the first week of recovery.

Those who survived the initial blast were driven out of cities to die or recover.

Even years after the bombings, radiation exposure caused long-term health effects and additional casualties among survivors.

Leukaemia cases began to rise approximately two years after the attacks, peaking between four and six years later. For other cancers, the increased risk linked to radiation began to emerge about a decade post-exposure.

One notable survivor was Sadako Sasaki.

The two-year-old was having breakfast with her family approximately 1.7km from the hypocenter, when the Hiroshima bomb detonated.

Ten years later, she began to show symptoms of leukaemia.

During her time in the hospital, Sadako was inspired by the Japanese legend that a wish would be granted if a person folded 1,000 paper cranes.

Sadako died in 1955 at the age of 12, surrounded by family with 1,300 origami cranes hanging overhead in her room.

Civilian casualties by country in World War II