DISASTER

Hiroshima, 64 years ago

Today, August 6th, marks 64 years since the atomic bombing of Hiroshima, Japan by the United States at the end of World War II. Targeted for military reasons and for its terrain (flat for easier assessment of the aftermath), Hiroshima was home to approximately 250,000 people at the time of the bombing. The U.S. B-29 Superfortress bomber "Enola Gay" took off from Tinian Island very early on the morning of August 6th, carrying a single 4,000 kg (8,900 lb) uranium bomb codenamed "Little Boy". At 8:15 am, Little Boy was dropped from 9,400 m (31,000 ft) above the city, freefalling for 57 seconds while a complicated series of fuse triggers looked for a target height of 600 m (2,000 ft) above the ground. At the moment of detonation, a small explosive initiated a super-critical mass in 64 kg (141 lbs) of uranium. Of that 64 kg, only .7 kg (1.5 lbs) underwent fission, and of that mass, only 600 milligrams was converted into energy - an explosive energy that seared everything within a few miles, flattened the city below with a massive shockwave, set off a raging firestorm and bathed every living thing in deadly radiation. Nearly 70,000 people are believed to have been killed immediately, with possibly another 70,000 survivors dying of injuries and radiation exposure by 1950. Today, Hiroshima houses a Hiroshima Peace Memorial Museum near ground zero, promoting a hope to end the existence of all nuclear weapons.

A Japanese soldier walks through a leveled area in Hiroshima, Japan in September of 1945, one month after the detonation of a nuclear bomb above the city. From a series of U.S. Navy photographs depicting the suffering and ruins that resulted from the blast. (U.S. Department of Navy)

An aerial view of Hiroshima, viewed some time shortly before the bomb was dropped on it in August of 1945. The scene shows a very densely built-up area of the city on the Motoyasu River looking upstream. (Hiroshima: The United States Strategic Bombing Survey Archive, International Center of Photography, Purchase, with funds provided by the ICP Acquisitions Committee, 2006) #

An early photograph of Hiroshima, before August 1945, looking upstream on the Motoyasu River toward what would become the most famous of all Hiroshima landmarks - the domed Hiroshima Prefectural Industrial Promotion Hall, immediately adjacent to ground zero. The building was originally designed by Czech architect Jan Letzel and completed in April 1915. (Hiroshima: The United States Strategic Bombing Survey Archive, International Center of Photography, Purchase, with funds provided by the ICP Acquisitions Committee, 2006)

Detail from a U.S. Air Force map of Hiroshima, pre-bombing, circles drawn at 1,000 foot intervals radiating out from ground zero, the site directly under the explosion. (U.S. National Archives and Records Administration)

Commander A.F. Birch (left), shown numbering the bomb codenamed "Little Boy" unit L-11, before loading it on trailer in Assembly Bldg. #1, prior to it being loaded aboard the B-29 Superfortress bomber "Enola Gay", on the base of the 509th Composite Group at Tinian Island in the Marianas Islands in 1945. Physicist Dr. Norman Ramsey stands at right - he would later go on to win the Nobel Prize in Physics in 1989.

"Little Boy" unit rests on a trailer cradle in a pit below the open bomb bay doors of the B-29 Superfortress bomber "Enola Gay" on the 509th Composite Group base at Tinian Island in the Marianas Islands in 1945. Little Boy was 3 m (10 ft) long, and weighed 4,000 kg (8,900 lb), but only carried contained 64 kg (141 lbs) of uranium which would be used to create a nuclear chain reaction, and resulting explosion

Shortly after 8:15 am, August 5, 1945, looking back at the growing "mushroom" cloud above Hiroshima. When a portion of the uranium in the bomb underwent fission, and was transformed instantly into an energy of about 15 kilotons of TNT (about 6.3 × 10¹³ joules), heating a massive fireball to a temperature of 3,980 C (7,200 F). The superheated air and smoke rapidly rose through the atmosphere like a giant bubble, dragging a column of smoke up with it. By the time this photo was made, smoke had billowed 20,000 feet above Hiroshima while smoke from the burst of the first atomic bomb had spread over 10,000 feet on the target at the base of the column

A view of destruction in Hiroshima, in the autumn of 1945, across one of the branches of the river that cut across the delta the city is centered on. (Hiroshima: The United States Strategic Bombing Survey Archive, International Center of Photography, Purchase, with funds provided by the ICP Acquisitions Committee, 2006)

Bomb damage to Okita Iron Works, Hiroshima, Japan. November 7th, 1945. (U.S. National Archives)

This patient (photographed by Japanese forces on October 2nd, 1945) was about 6,500 feet from ground zero when the rays struck him from the left. His cap was sufficient to protect the top of his head against flash burns

A man looks over the expanse of ruins left by the explosion of the atomic bomb on in Hiroshima, Japan. (AP Photo)

Members of the U.S. Army examine the area around ground zero in Hiroshima, Japan in the autumn of 1945.

Visitors view a panorama showing the aftermath of the atomic bomb attack, at a museum at the Hiroshima Peace Memorial Park on July 27, 2005 in Hiroshima. Japan. 

The Peace Flame has burned for the atomic bomb victims at the Memorial Cenotaph at Hiroshima Peace Memorial Park in Hiroshima, western Japan, Tuesday, Aug. 4, 2009. The flame has burned continuously since it was lit on August 1, 1964. It symbolizes the anti-nuclear resolve to burn the flame "until the day when all such weapons shall have disappeared from the earth

On the morning of 6 August 1945 an American B-29 bomber, the 'Enola Gay', dropped the first atomic bomb used in warfare on the Japanese city of Hiroshima.

The bomb was dropped by parachute and exploded 580m (1,900ft) above the ground. Between 60,000 and 80,000 people were killed instantly. The heat from the bomb was so intense that some people simply vanished in the explosion. Many more died of the long-term effects of radiation sickness. The final death toll was calculated at 135,000. As well as residents of Hiroshima, the victims included Koreans who had been forced to come to Japan as labourers, and American prisoners-of-war who were imprisoned in Hiroshima.

The blast destroyed more than ten square kilometres (six square miles) of the city. And the intense heat of the explosion then created many fires, which consumed Hiroshima and lasted for three days, trapping and killing many of the survivors of the initial blast. Thousands of people were made homeless and fled the devastated city.

Hiroshima was chosen because it had not been targeted during the US Air Force's conventional bombing raids on Japan, and was therefore regarded as being a suitable place to test the effects of an atomic bomb. It was also an important military base. The Allies feared that any conventional attempt to invade the Japanese home islands would result in enormous casualties, and the bomb was seen as a way of bringing the war against Japan to a swift conclusion. In addition, it may also have been a way of demonstrating American military superiority over the Soviet Union.

On the morning of 9 August, the Americans dropped a second, bigger atomic bomb. The original target was Kokura, but this was obscured by cloud so the bomb was dropped on nearby Nagasaki, an important port. About 40,000 people were killed instantly and a third of the city was destroyed. The final death toll was calculated as at least 50,000.

Among those in the plane that dropped the bomb on Nagasaki was the British pilot Leonard Cheshire. He later recalled the cloud caused by the atomic blast in Martin Gilbert's Second World War:

'Obscene in its greedy clawing at the earth, swelling as if with its regurgitation of all the life that it had consumed.'

On 14 August, Japan agreed to the Allies' terms of surrender. At midday on the following day, Emperor Hirohito broadcast the news to the Japanese people. It was the first time his voice had been heard on the radio.

After the war, Hiroshima was rebuilt as a peace memorial city and the closest surviving building to the epicentre was designated the Hiroshima Peace Memorial.

At 2:45 in the morning of August 6, 1945, an American B-29 bomber flew north from Tinian Island in the Marianas toward Japan. Three and a half hours later, over the city of Hiroshima, the Enola Gay dropped an 8,900-pound atomic weapon from its specially modified bomb bay. Two thousand feet above the ground, the bomb, dubbed "Little Boy" by its makers, detonated, leveling almost 90% of the city.

On August 9, another B-29, Bockscar, set out for the Kokura Arsenal on the southwest Japanese island of Kyushu. Foul weather, however, persuaded the pilot to proceed instead toward Nagasaki, the home of a Mitsubishi torpedo factory. Over this secondary target Bockscar dropped a larger device, code-named "Fat Man." Local geography spared Nagasaki from the near total devastation suffered by Hiroshima; only one third of the city was destroyed.

Fat Man and Little Boy

Fat Man and Little Boy, both weapons of unparalleled destructive power, were actually quite different. Little Boy, fueled by highly enriched uranium-235, was triggered by a simple "gun" mechanism; a small, slug-shaped piece of uranium was fired down a barrel into a larger, cup-shaped piece. This elementary design generated a destructive force of about 15 kilotons—the equivalent of 15,000 tons of TNT.

A much more complex implosion-type device triggered Fat Man. It consisted of a plutonium core surrounded by high explosives wired to explode simultaneously. The shock waves from these conventional explosions triggered the fission of the plutonium, which yielded a 22 kiloton explosion.

The attacks on Hiroshima and Nagasaki had a devastating psychological impact on the already weakened Japanese. Emperor Hirohito accepted the U.S.' terms of surrender on August 14. On September 2, Japan signed an official declaration of surrender aboard the U.S.S. Missouri.

The Controversy

U.S. military officials believed that such a massive demonstration of U.S. military power was the only reasonable way to force an unconditional Japanese surrender. Though the islands' supply lines had been cut, the Japanese air force was a shambles, and Tokyo was nearly in ruins, it was still widely believed that no conventional military action short of an invasion could make Japan surrender. In her entire history, Japan had never been invaded or defeated. Even after the destruction of Hiroshima, she refused to capitulate.

The decision to bomb Hiroshima and Nagasaki—the first and last use of atomic weapons in combat—remains one of the most controversial in military history. Altogether, the two bombings killed an estimated 110,000 Japanese citizens and injured another 130,000. By 1950, another 230,000 Japanese had died from injuries or radiation. Though the two cities were nominally military targets, the overwhelming majority of the casualties were civilian.

Needless Tragedy or Prudent Military Decision?

Because of robust Japanese defenses and the topography of the islands themselves, an amphibious assault would have taken a heavy toll on U.S. forces. Military officials estimated that such an invasion might have incurred up to a million U.S. casualties, with corresponding Japanese military and civilian losses. Two fire bombing raids on Tokyo earlier in 1945 had already killed 140,000 citizens and injured a million more. The bombings of Hiroshima and Nagasaki, then, might actually have spared hundreds of thousands of Japanese and American lives.

This justification, however, is not universally accepted. Some sources' estimates of U.S. casualties are significantly lower—perhaps as low as 50,000 men. It is also not entirely clear that an unconditional Japanese surrender was impossible, especially if Russia had entered the war before the bombing (Russia officially declared war on Japan on August 8, two days after the destruction of Hiroshima).

Some suggest that Truman, fearing a Soviet attempt to dominate the postwar Asian order as it had the Eastern European, ordered the bombing to force Japan's surrender before Russia had the chance to enter the fray (and thus earn the right to affect the peace settlement). Truman may also have wanted to intimidate his potential rival Stalin with the United States' new destructive capability.

Whether the bombings of Hiroshima and Nagasaki constituted a needless tragedy or a prudent military decision will never be certain. Those who made the decision, as well as most of the survivors, are long gone. The effects, though—the lingering scourge of radiation, the memory of the ghastly civilian casualties, the psychological impact of simply knowing that such a destructive force exists—remain. One can only hope that those who now wield the tools of armageddon will remember the lessons of Hiroshima and Nagasaki for a long time to come.

Originally found from:
http://www.boston.com/bigpicture/2009/08/hiroshima_64_years_ago.html