Atomic Bombing of Hiroshima (1945): The First Nuclear Attack

The atomic bombing of Hiroshima on 6 August 1945 was the first use of a nuclear weapon in war. An American B-29 bomber, the Enola Gay, dropped a uranium bomb known as Little Boy on the Japanese city of Hiroshima, destroying most of it in an instant and killing tens of thousands of people outright.

By the end of 1945 the bombing had killed an estimated 90,000 to 140,000 people. Three days later a second bomb was dropped on Nagasaki, and on 15 August Japan announced its surrender. The decision to use the bomb has been debated ever since, and Hiroshima has become a worldwide symbol of the dangers of nuclear weapons.

Background

The atomic bomb was the product of the Manhattan Project, the secret American programme launched with British and Canadian participation in 1942, after scientists warned that Nazi Germany might build such a weapon. By the summer of 1945 Germany had surrendered, but the war against Japan continued.

American forces had suffered heavy losses at Iwo Jima and Okinawa, and the conventional bombing of Japanese cities had already killed hundreds of thousands of civilians, most terribly in the firebombing of Tokyo in March 1945. Military planners were preparing an invasion of the home islands, scheduled to begin on Kyushu in November 1945.

The first atomic device was tested successfully in the New Mexico desert on 16 July 1945, the Trinity test. At the Potsdam Conference, President Harry S. Truman told Stalin, without details, that the United States had a powerful new weapon. On 26 July the United States, Britain and China issued the Potsdam Declaration, demanding Japan’s unconditional surrender and warning of “prompt and utter destruction” if it refused. The Japanese government did not accept it.

Choosing the target

A Target Committee of military officers and scientists had recommended cities that were large, militarily significant and not yet badly damaged by conventional raids, so that the bomb’s effect could be measured. Kyoto was removed from the list at the insistence of Secretary of War Henry L. Stimson because of its cultural and historical importance.

Hiroshima, a city of roughly 340,000–350,000 people, was the headquarters of the Second General Army, which commanded the defence of southern Japan, and an important port and supply base. Thousands of soldiers were stationed there. It had been spared major air raids. On 25 July the US Army issued a written order to the commander of its strategic air forces in the Pacific to drop the first bomb on one of the selected targets as soon as weather permitted after about 3 August.

The mission

The bombing was carried out by the 509th Composite Group, a specially trained unit of the US Army Air Forces commanded by Colonel Paul Tibbets. It was based on North Field on the island of Tinian in the Mariana Islands.

In the early hours of 6 August 1945 Tibbets took off in a B-29 he had named Enola Gay after his mother. Two other B-29s accompanied it, one carrying scientific instruments and one equipped for photography, while weather aircraft had gone ahead. Navy Captain William S. Parsons, the weaponeer, completed the arming of the bomb in flight, to avoid the risk of a nuclear explosion if the aircraft crashed on take-off.

The weather over Hiroshima was clear. The bomb was released at about 31,000 feet and fell for some 43 seconds. The aiming point was the T-shaped Aioi Bridge in the city centre. Little Boy exploded at 8:15 am at a height of about 580–600 metres, close to the Shima Hospital, a few hundred metres from the bridge.

The destruction

The explosion released energy equivalent to an estimated 15 kilotons of TNT, with a margin of a few kilotons either way. A fireball hundreds of metres wide formed in a fraction of a second, with temperatures at the ground directly beneath reaching several thousand degrees Celsius. People near the hypocentre were killed instantly; some left only shadows on stone.

The blast wave flattened most buildings within about 2 km, and fires then swept the city. About 12 square kilometres (4.7 square miles) of the city was destroyed, and roughly two-thirds of its buildings were destroyed or badly damaged. Most of Hiroshima’s doctors and nurses were killed or injured, and nearly all its hospitals were destroyed, leaving survivors with almost no medical help.

Later that day, “black rain” containing radioactive fallout and soot fell on parts of the city and surrounding areas. In the weeks that followed, many people who had seemed uninjured fell ill and died from radiation sickness, with symptoms such as hair loss, bleeding and fever.

The victims

The victims included Japanese civilians of all ages, soldiers, and thousands of schoolchildren who had been mobilised to clear firebreaks in the city centre. Among the dead were many Koreans, a large number of them labourers brought to Japan during the colonial period, as well as Chinese and Southeast Asian students and a small number of American prisoners of war held in the city.

Survivors, known in Japanese as hibakusha, faced long-term consequences. Studies by the Atomic Bomb Casualty Commission and its successor, the Radiation Effects Research Foundation, found increased rates of leukaemia and other cancers. Many hibakusha also faced discrimination in employment and marriage because of fears about radiation.

The response and the surrender

Sixteen hours after the attack, the White House released a statement by Truman announcing that an atomic bomb had been dropped and warning Japan’s leaders that if they did not accept American terms they could expect “a rain of ruin from the air”. The Japanese government and military were slow to accept that a single bomb had caused such destruction.

On 8 August the Soviet Union declared war on Japan, and early on 9 August Soviet forces invaded Manchuria. Later that morning the atomic bombing of Nagasaki took place. After a deadlocked government and an imperial conference, Emperor Hirohito intervened in favour of accepting the Potsdam terms, leading to the surrender of Japan announced on 15 August and signed on 2 September 1945.

The debate over the decision

The decision to use the bomb was popular in the United States at the time, when it was seen as having ended the war and spared American lives. In 1947 Stimson published an article defending it, arguing that an invasion could have cost a million American casualties, a figure that later historians have questioned.

Critics, including some historians and several senior American officers after the war, have argued that Japan was already near defeat, that a modification of surrender terms to protect the emperor or the shock of Soviet entry into the war might have ended it, and that a demonstration of the bomb on an uninhabited area could have been tried. Others respond that Japan’s military leaders were still determined to fight on, and that the bombs, together with the Soviet declaration of war, gave the emperor and the peace faction the opportunity to impose surrender.

The debate has also involved moral questions about the deliberate targeting of a city full of civilians. In 1995 a planned exhibition at the Smithsonian Institution’s National Air and Space Museum in Washington, featuring the Enola Gay, was scaled back after a major public controversy.

Public understanding of what had happened on the ground came slowly. During the Allied occupation of Japan, censorship restricted the publication of reports and images of the bombings’ effects. In the United States, John Hersey’s long article Hiroshima, published in The New Yorker in August 1946 and soon afterwards as a book, told the stories of six survivors and brought the human cost of the bomb to a mass audience for the first time.

Legacy

Hiroshima was rebuilt after the war and declared a “Peace Memorial City” by law in 1949. The Peace Memorial Park, designed by the architect Kenzo Tange, stands near the hypocentre. The ruined Prefectural Industrial Promotion Hall, now known as the Atomic Bomb Dome or Genbaku Dome, was preserved and became a UNESCO World Heritage Site in 1996.

The story of Sadako Sasaki, a girl exposed to the bomb at the age of two who died of leukaemia in 1955 and folded paper cranes during her illness, made the paper crane an international symbol of peace. Every year on 6 August a memorial ceremony is held in the city at 8:15 am. In 2016 Barack Obama became the first sitting US president to visit Hiroshima.

Timeline

• 1945, 16 July: The Trinity test in New Mexico proves the atomic bomb works.
• 1945, 26 July: The Potsdam Declaration calls on Japan to surrender unconditionally.
• 1945, 6 August, 2:45 am: Enola Gay takes off from Tinian.
• 1945, 6 August, 8:15 am: Little Boy explodes over Hiroshima.
• 1945, 6 August (Washington time): Truman announces the bombing.
• 1945, 9 August: A second atomic bomb destroys much of Nagasaki.
• 1945, 15 August: Emperor Hirohito broadcasts Japan’s acceptance of surrender.
• 1996, December: The Atomic Bomb Dome is inscribed as a UNESCO World Heritage Site.

Why it matters

Hiroshima marked the beginning of the nuclear age. The bombing helped bring the Second World War to an end, but it also revealed the power of weapons capable of destroying entire cities, shaped the Cold War arms race and continues to inform debates about nuclear deterrence, disarmament and the ethics of war.