This index almost left Hiroshima out, on the reasoning that strategic bombing was a policy rather than an incident. That was the wrong call. It has a date, a time, an aircraft, an aiming point and a decision, and it produced the largest death toll any single weapon has ever caused.
What happened
At 08:15 on 6 August 1945, a US B-29 released a uranium gun-type bomb over Hiroshima. It detonated roughly 600 metres above the city with a yield of about 15 kilotons.
The city was flattened across a radius of a mile or more. Fires merged into a firestorm. People near the hypocentre were killed instantly; further out, deaths came from burns, blast injuries, collapsed buildings and, over the following weeks and months, radiation sickness.
Why the time of day matters
It was a weekday morning. People were travelling to work and school, and thousands of schoolchildren were outdoors in the city centre on firebreak demolition work. The hour maximised the number of people in the open.
The toll, and why the range is so wide
Four things make a precise count impossible. The city's records were destroyed along with the offices holding them. The wartime population was uncertain, including conscripted workers and Korean forced labourers. Deaths continued for years from radiation-related illness, so any total depends on where you stop counting. And whole families died together, leaving nobody to report them.
A range with its reasons attached is the honest presentation, as it is for every casualty figure in this archive.
The same counting problems recur at a smaller scale throughout this archive, from the 156 identified at Minab to the twelve to eighteen killed in the 2007 Baghdad airstrike, most of whom were never named at all.
Was Hiroshima a military target?
This is the question the category depends on, and both answers have real content.
| The case that it was | The case that the city was the target |
|---|---|
| Hiroshima held an army headquarters and was a military port | The aiming point was a bridge near the commercial centre, not the port or the barracks |
| It had industry supporting the war | A 15-kiloton weapon cannot be aimed at a factory within a city |
| It had been deliberately left unbombed, so effects could be measured | Which means the intact civilian population was part of what was being assessed |
The honest finding is that the distinction the modern rules rest on does not survive contact with this weapon. You cannot separate a military objective from the civilians around it when the effect radius is the city.
Why this index needed a third category
Neither collateral nor massacre
My Lai was soldiers killing people they could see were unarmed. Kunduz was a mistaken target. Hiroshima is neither. The city was the target, and the deaths of its inhabitants were the expected and accepted result, not an error and not an intimate act of killing.
Calling it collateral damage misuses the term, because civilians were not incidental. Calling it a massacre in the My Lai sense misses that it was a policy decision taken at the highest level. It belongs in its own column, alongside the Tokyo firebombing and Nagasaki.
The people who lived, and what happened to them
A count of the dead misses the group Hiroshima is most distinctive for. Survivors of both bombings became a recognised category in Japan, with health records maintained over decades.
Their experience produced something no other case in this index has: a long-running medical study of what a single weapon does to a population over a lifetime. Elevated rates of leukaemia appeared within a few years, other cancers over decades, and children exposed in the womb showed developmental effects.
Survivors also faced discrimination at home, in employment and in marriage, on fears about inherited effects that the research did not bear out. That is a form of harm no casualty figure records, and it is the same gap described in the page on the wider cost of war to civilians.
What Hiroshima set in place
Every rule this archive measures other incidents against was written afterwards and partly because of it. The Geneva Conventions of 1949 and the 1977 protocols that codified distinction, proportionality and precaution were drafted by people who had seen what area attacks on cities produced.
So the largest entry in this index is also the one that is hardest to judge by the index's own standards: the standards did not exist yet, and they exist now partly because of this. The rules are set out here, and the full index is here.
Questions people ask about this
How many people died at Hiroshima?
Was Hiroshima a military target?
Why is it not classed as collateral damage?
Where this comes from
- Atomic bombings of Hiroshima and Nagasaki — Wikipedia
- Counting the dead at Hiroshima and Nagasaki — Bulletin of the Atomic Scientists
- Atomic bombings of Hiroshima and Nagasaki — Encyclopaedia Britannica
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