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World War II Coroner's Fact Sheet About the After Effects of the Bombs

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World War II Coroner's Fact Sheet About the After Effects of the Bombs

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On August 6, 1945, during World War II (1939-45), an American B-29 bomber dropped the world's first deployed atomic bomb over the Japanese city of Hiroshima. The explosion immediately killed an estimated 80,000 people; tens of thousands more would later die of radiation exposure. Three days later, a second B-29 dropped another A-bomb on Nagasaki, killing an estimated 40,000 people. Japan's Emperor Hirohito announced his country's unconditional surrender in World War II in a radio address on August 15, citing the devastating power of "a new and most cruel bomb."

The Manhattan Project

Even before the outbreak of war in 1939, a group of American scientists-many of them refugees from fascist regimes in Europe-became concerned with nuclear weapons research being conducted in Nazi Germany. In 1940, the U.S. government began funding its own atomic weapons development program, which came under the joint responsibility of the Office of Scientific Research and Development and the War Department after the U.S. entry into World War II. The U.S. Army Corps of Engineers was tasked with spearheading the construction of the vast facilities necessary for the top-secret program, codenamed "The Manhattan Project " (for the engineering corps' Manhattan district).

Over the next several years, the program's scientists worked on producing the key materials for nuclear fission-uranium-235 and plutonium (Pu-239). They sent them to Los Alamos, New Mexico, where a team led by J. Robert Oppenheimer worked to turn these materials into a workable atomic bomb. Early on the morning of July 16, 1945, the Manhattan Project held its first successful test of an atomic device -a plutonium bomb-at the Trinity test site at Alamogordo, New Mexico.

No Surrender for the Japanese

By the time of the Trinity test, the Allied powers had already defeated Germany in Europe. Japan, however, vowed to fight to the bitter end in the Pacific, despite clear indications (as early as 1944) that they had little chance of winning. In fact, between mid-April 1945 (when President Harry Truman took office) and mid-July, Japanese forces inflicted Allied casualties totaling nearly half those suffered in three full years of war in the Pacific, proving that Japan had become even more deadly when faced with defeat. In late July, Japan's militarist government rejected the Allied demand for surrender put forth in the Potsdam Declaration, which threatened the Japanese with "prompt and utter destruction" if they refused.

General Douglas MacArthur and other top military commanders favored continuing the conventional bombing of Japan already in effect and following up with a massive invasion, codenamed "Operation Downfall." They advised Truman that such an invasion would result in U.S. casualties of up to 1 million. In order to avoid such a high casualty rate, Truman decided-over the moral reservations of Secretary of War Henry Stimson, General Dwight Eisenhower and a number of the Manhattan Project scientists-to use the atomic bomb in the hopes of bringing the war to a quick end. Proponents of the A-bomb-such as James Byrnes, Truman's secretary of state-believed that its devastating power would not only end the war, but also put the U.S. in a dominant position to determine the course of the postwar world.

'Little Boy' and 'Fat Man' Are Dropped

Hiroshima, a manufacturing center of some 350,000 people located about 500 miles from Tokyo, was selected as the first target. After arriving at the U.S. base on the Pacific island of Tinian, the more than 9,000-pound uranium-235 bomb was loaded aboard a modified B-29 bomber christened Enola Gay (after the mother of its pilot, Colonel Paul Tibbets). The plane dropped the bomb-known as "Little Boy"-by parachute at 8:15 in the morning, and it exploded 2,000 feet above Hiroshima in a blast equal to 12-15,000 tons of TNT, destroying five square miles of the city.

Hiroshima's devastation failed to elicit immediate Japanese surrender, however, and on August 9 Major Charles Sweeney flew another B-29 bomber, Bockscar, from Tinian. Thick clouds over the primary target, the city of Kokura, drove Sweeney to a secondary target, Nagasaki, where the plutonium bomb "Fat Man" was dropped at 11:02 that morning. More powerful than the one used at Hiroshima, the bomb weighed nearly 10,000 pounds and was built to produce a 22-kiloton blast. The topography of Nagasaki, which was nestled in narrow valleys between mountains, reduced the bomb's effect, limiting the destruction to 2.6 square miles.

Aftermath of the Bombing

At noon on August 15, 1945 (Japanese time), Emperor Hirohito announced his country's surrender in a radio broadcast. The news spread quickly, and "Victory in Japan" or "V-J Day" celebrations broke out across the United States and other Allied nations. The formal surrender agreement was signed on September 2, aboard the U.S. battleship Missouri, anchored in Tokyo Bay.

Because of the extent of the devastation and chaos-including the fact that much of the two cities' infrastructure was wiped out-exact death tolls from the bombing of Hiroshima and Nagasaki remain unknown. However, it's estimated roughly 70,000 to 135,000 people died in Hiroshima and 60,000 to 80,000 people died in Nagasaki, both from acute exposure to the blasts and from long-term side effects of radiation.

Fact Check

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Bombing of Hiroshima and Nagasaki - Causes, Impact & Lives Lost

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On August 6, 1945, during World War II (1939-45), an American B-29 bomber dropped the world's first deployed atomic bomb over the Japanese city of Hiroshima, immediately killing 80,000 people. Three days later, a second bomb was dropped on Nagasaki, killing an estimated 40,000 people.

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What is your city were hit by the atomic bomb?

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What is your city were hit by the atomic bomb?

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While the graying Hiroshima Generations who survived the atomic bomb attack seven decades ago are struggling to pass their memories to the younger generations, much of the world has allowed that fateful morning on Aug 6, 1945 to slip from their minds.

About 66,000 people, mostly civilians, perished, according to a report prepared by the US Army one year after the attack. Another 69,000 were injured and tens of thousands more were affected by radiation disease.

But how to show the damage more clearly? We've developed an application that allows you to visualize the damage of the same atomic bomb on another location in today's world, such as your hometown. You may be surprised at the extent of the damage.

The estimated damage and fatalities were made based on several reports: The Atomic Bombings of Hiroshima and Nagasaki prepared by the Manhattan Engineer District, a part of the Manhattan Project that created the atomic bomb, The Effects of Atomic Bombs on Hiroshima and Nagaski prepared by the United States Strategic Bombing Survey, and computed data in Medical Effects of the Atomic Bomb in Japan by A. W. Oughterson and S. Warren. The estimation does not take into account the differences in geography and weather.

If you prefer a more scientific estimation of the damage and the options to choose different atomic bombs, Alex Wellerstein, a historian of science at the Stevens Institute of Technology, has created a simulator called Nukemap.

If you wonder what was the damage done to Hiroshima then, the interactive image below shows the aerial photos of Hiroshima before and after the attack. Move the slider to see full images. The bottom image is a Google satellite image of today's Hiroshima.
UPDATE: A previous version of this story incorrectly stated that the images showing Hiroshima before and after the bombing are satellite images. We regret the error. This story is part of the Hiroshima Generations series supported by the United States-Japan Foundation. A few other stories included in this series: Marco Werman: The Bomb saved my mom This Hiroshima survivor's family now includes American in-laws After the A-bomb survivors die, who will be Hiroshima's memory keepers?

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What if your hometown were hit by the Hiroshima atomic bomb?

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While the graying Hiroshima Generations who survived the atomic bomb attack seven decades ago are struggling to pass their memories to the younger generations, much of the world has allowed that fateful morning on Aug 6, 1945 to slip from their minds.

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Hiroshima Sadako and the Thousand Paper Cranes Exhibit Encouraging the Elimination of Atomic Bombs

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Hiroshima Sadako and the Thousand Paper Cranes Exhibit Encouraging the Elimination of Atomic Bombs

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A Young Girl's Death from the A-bomb --Sadako Sasaki, 12 Years of Age Sadako's 4,675 Days of Life The Sadako in Me Hiroshima in 1955, the Year of Sadako's Death Sadako Through the Years -From Hiroshima to the World -Toward Construction of the Children's Peace Monument The Sadako Story Spreads FinallyIndividuals and Groups Contributors to This Exhibition Retarn to the Special Exhibit TOP

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Footage of the bombing of Nagasaki (silent film) The bomb was called Fat Man and Bockscar was the plane that carried it.  

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Footage of the bombing of Nagasaki (silent film) The bomb was called Fat Man and Bockscar was the plane that carried it.  

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Unedited footage of the bombing of Nagasaki (silent)

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This silent film shows the final preparation and loading of the "Fat Man" bomb into "Bockscar," the plane which dropped the bomb on Nagasaki. It then shows the Nagasaki explosion from the window of an observation plane. This footage comes from Los Alamos National Laboratory.

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1946 film of footage showing the destruction of Hiroshima and Nagasaki

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1946 film of footage showing the destruction of Hiroshima and Nagasaki

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This 1946 film shows actual footage of the atomic bomb destruction of Hiroshima and Nagasaki Japan

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During the final stages of World War II in 1945, the Allies of World War II conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan. These two events are the only use of nuclear weapons in war to date.

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Interview with Colonel-Paul-Tibbete who flew the Enola Gay plane that dropped the atomic bomb

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Little Boy-the bomb dropped on Hiroshima

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Little Boy-the bomb dropped on Hiroshima