The cost

The toll

No one knows exactly how many people the bombs killed. Different bodies counted at different times, over different periods, and their figures are set out side by side here.

The exact number of dead will never be known. Records were destroyed, and in some families no one was left to report a death. Soldiers, conscripted workers and people in the city for the day were on no list of residents. The first American counts used lower population figures and shorter periods. ^{Sources: 10, 13}

Most of the people killed were civilians. The dead included thousands of Koreans and a small number of Allied prisoners of war. ^{Sources: 1, 10, 11, 15, 16, 17}

In Hiroshima, a city survey in 1946 counted 76,327 buildings. Of these, 51,787 were destroyed or burnt out and 6,180 were partly destroyed: nine in ten were damaged. Fire swept about 13 square kilometres. ^{Sources: 1, 13, 18, 19}

Nagasaki lies in steep valleys, and the hills held in the worst of the damage. Even so, 18,409 houses were damaged, about 36 per cent of the houses in the city. ^{Sources: 12, 13}

How people died

The bombs killed in three ways: heat, blast and radiation. Fires then spread through the wreckage. ^{Sources: 18}

Near the hypocentre in Hiroshima the ground reached 3,000 to 4,000 degrees Celsius. Bare skin was burned as far as 3.5 kilometres away. Within 2 kilometres, most wooden houses fell and the area burned. ^{Sources: 18}

Within 1.2 kilometres of the hypocentre, about half the people died that day. ^{Sources: 11}

Many people who seemed unhurt fell ill within days or weeks, and many of them died. Radiation also harmed people who came into the city afterwards, to search for family or to help. ^{Sources: 18}

In 1946 American investigators estimated that burns caused 20 to 30 per cent of deaths, other injuries 50 to 60 per cent, and radiation sickness 15 to 20 per cent. These were estimates made from incomplete records. ^{Sources: 13}

After the bombing a black rain fell on areas around Hiroshima. For decades people caught in it outside an officially drawn zone were not recognised as survivors. After a court ruling in July 2021, people exposed to the black rain who have one of 11 listed illnesses can be certified, since April 2022. ^{Sources: 20, 21}

The survivors

The survivors are called hibakusha, which means atomic bomb affected people. ^{Sources: 22}

Japan’s first law for survivors came into force in April 1957, giving them health checks and medical care. A second law followed in 1968. The present Atomic Bomb Survivors’ Support Law came into force in July 1995. ^{Sources: 7}

Four groups can hold a survivor’s health certificate: ^{Sources: 21}

• people who were in or near the cities when the bombs fell
• people who went within about 2 kilometres of a hypocentre in the two weeks after
• people exposed in other ways, such as those who cared for the injured and the dead
• babies who were then in the womb of someone in these groups

At the end of March 2026, 91,105 people held a certificate. Their average age was 86.66. ^{Sources: 9} The number peaked at 372,264 at the end of the 1980 financial year. ^{Sources: 23}

Many survivors met prejudice. Some were turned down for jobs or for marriage, out of fear of illness or of harm to their children. ^{Sources: 22, 24}

Tens of thousands of Koreans were in Hiroshima, many brought to Japan as labourers. No reliable count of Korean deaths exists. A memorial to the Korean victims was moved into the Peace Park in 1999. ^{Sources: 25}

For years the support laws did not reach survivors who lived abroad. Since December 2008 they can apply from overseas. In March 2026 about 2,061 certificate holders lived outside Japan, most of them in Korea and the Americas. ^{Sources: 7, 24, 26}

Long-term health

Since 1950 the Life Span Study has followed about 120,000 people: about 94,000 survivors and 27,000 people who were not in the cities. It is run by the Radiation Effects Research Foundation, a Japanese and American body. ^{Sources: 10, 27}

Leukaemia came first. Among study members with a measurable dose, 204 died of leukaemia between 1950 and 2000. RERF estimates that 94 of those deaths, 46 per cent, were caused by the bombs’ radiation. The excess peaked after six to eight years. ^{Sources: 28}

Other cancers came later. From 1958 to 1998, 7,851 solid cancers were found among 44,635 study members with a measurable dose. RERF puts 848 of them, 10.7 per cent, down to radiation. ^{Sources: 29} The extra leukaemia has now virtually disappeared, but the extra risk of other cancers remains. ^{Sources: 10}

Babies exposed in the womb, especially 8 to 15 weeks after conception, were more likely to have a severe mental disability and to be shorter as adults. ^{Sources: 30}

RERF has studied tens of thousands of survivors’ children. It has found no evidence of clinical or subclinical effects so far. It adds that this does not necessarily mean that no effects exist. ^{Sources: 10, 31}

How the war ended

The bombs fell in the last weeks of the war. These are the steps by which Japan surrendered, in local time.

1. 26 July

   The Potsdam Declaration

   The leaders of the United States, Britain and China call on Japan’s armed forces to surrender without conditions, or face “prompt and utter destruction”. The declaration says nothing about the Emperor.^{Sources: 32, 33, 34}

2. 28 July

   Japan’s answer

   Prime Minister Suzuki tells the press that Japan will ignore the declaration. The Allies take his word, mokusatsu, as a rejection.^{Sources: 35, 36}

3. 6 August

   Hiroshima

   Little Boy is dropped on Hiroshima.^{Sources: 1, 2}

4. 8 August

   The Soviet Union declares war

   Soviet forces invade Manchuria the next day.^{Sources: 2, 34, 36}

5. 9 August

   Nagasaki, and a divided council

   Japan’s war council learns of Nagasaki during the meeting and cannot agree. At an Imperial conference that night the council is still split three to three, and the Emperor backs accepting with one condition.^{Sources: 2, 3, 34, 37, 38}

6. 10 August

   The offer

   Japan offers to accept, provided the declaration does not prejudice “the prerogatives of His Majesty as a sovereign ruler”.^{Sources: 34, 36}

7. 11 August

   The reply

   The American reply, for the Allies, says the Emperor’s authority will be “subject to the Supreme Commander”, and Japan’s government will be set by “the freely expressed will of the Japanese people”.^{Sources: 2, 34}

8. 14 August

   The decision

   At a second Imperial conference the Emperor tells his ministers to accept, and that night he records a message to the nation. Army officers led by Major Kenji Hatanaka try to stop it. They fail, and the War Minister, Korechika Anami, takes his own life the next morning. At 19:00 Washington time, Truman announces that Japan has accepted.^{Sources: 5, 34, 36, 37, 38, 39, 40}

9. 15 August

   The broadcast

   At noon Tokyo time the Emperor’s recorded voice is broadcast to the nation. He speaks of “a new and most cruel bomb”, and does not use the word surrender.^{Sources: 4, 5, 37}

10. 2 September

    The signing

    Aboard USS Missouri in Tokyo Bay, Mamoru Shigemitsu and Yoshijiro Umezu sign for Japan. MacArthur accepts for the Allies, and Nimitz signs for the United States.^{Sources: 6, 41}

The debate

Whether the bombs were needed to end the war is still debated by historians. This page sets out the main positions in brief, and The decision and the debate sets them out in full, with the papers behind them. Neither takes a side. ^{Sources: 42, 43}

The traditional view was set out by the former Secretary of War, Henry Stimson, in 1947. It holds that the bombs ended the war quickly and spared the far greater loss of life an invasion would have caused. ^{Sources: 34, 44}

Revisionist historians, led by Gar Alperovitz, argue that Japan was close to surrender and that other paths were open, such as waiting for the Soviet Union to join the war, or assuring Japan it could keep its Emperor. ^{Sources: 34, 44}

Many historians sit between the two. Barton Bernstein judged it “very likely, though certainly not definite” that the war would have ended before an invasion without the bomb. ^{Sources: 34, 44}

Remembering

Each year on 6 August Hiroshima holds its Peace Memorial Ceremony, with a minute’s silence from 8:15, the moment of the bombing. On 9 August Nagasaki falls silent at 11:02. ^{Sources: 47, 48}

In Japan, 15 August is the Day to Commemorate the War Dead and Pray for Peace. A national ceremony remembers more than three million Japanese war dead, with a silence at noon. ^{Sources: 49}

Hiroshima’s cenotaph was designed by Kenzo Tange and completed on 6 August 1952. Its stone chest holds the register of the dead, of any nationality. The inscription reads: “Let all the souls here rest in peace; for we shall not repeat the evil.” ^{Sources: 50}

In August 2026 the Hiroshima register held 353,639 names, and Nagasaki’s held 204,708. Both list survivors who died at any time since, so they are not counts of the people the bombs killed. ^{Sources: 51, 52}

Sadako Sasaki was two when the bomb fell on Hiroshima. Ten years later she was found to have leukaemia. In hospital she folded paper cranes, hoping to live, and by the end of August 1955 she had folded more than 1,000. She died on 25 October 1955, aged 12. ^{Sources: 53}

Her classmates raised money across Japan for a monument to all the children who died. The Children’s Peace Monument was unveiled on 5 May 1958. About 10 million paper cranes are sent to it each year. ^{Sources: 54, 55}

On 11 October 2024 the Norwegian Nobel Committee awarded the Peace Prize to Nihon Hidankyo, the national organisation of hibakusha founded in 1956. It honoured the survivors’ work for a world free of nuclear weapons, and their witness that such weapons must never be used again. ^{Sources: 8}