Atomic Bomb on Hiroshima and Nagasaki Japan

Table of Contents


On August 6th, 1945 a modified B-29 bomber named “Enola Gay” dropped an atomic bomb named “Little Boy” on Hiroshima, Japan. Three days later on August 9th, 1945, another B-29 named “Bockscar” dropped an atomic bomb named “Fat Man” on Nagasaki, Japan. This is what ended World War 2 with Japan agreeing to surrender on August 15th, 1945, and signing an agreement to surrender on September 2nd, 1945 with World War 2 officially being over on September 3rd, 1945.


Who Invented the Atomic Bomb

Otto Hahn

In December of 1938, German Otto Hahn and his assistant Fritz Strassman discovered Nuclear fission which is splitting an atom with another particle causing a massive chain reaction of energy to be released.

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Several Jewish scientists that escaped from Europe to the United States wrote a letter to President Franklin D. Roosevelt about nuclear fission discovery. This included Albert Einstein, Enrico Fermi, and Leo Szilard.

President Roosevelt received the letter written by Albert Einstein and the other scientists which led him to have a special committee to review the findings. The committee was called the “Advisory Committee on Uranium” and was run by Lyman Briggs.

With a $6,000 budget to run experiments, the committee met in October of 1939 and began running tests and experiments on fission of Uranium. It only took the committee a month to report back to President Roosevelt that the fission of Uranium, while untested, had the potential to fuel submarines, but also create an atomic bomb stronger than anything ever known to man.

The advisory committee continued experiments and on March 2nd, 1940, John Dunning and his team verified Niels Bohr’s hypothesis. The hypothesis was that electrons revolve around the atomic nucleus and could jump from one energy level to another. John Dunning discovered that Uranium 235 is responsible for fission by slow neutrons and would be the required fuel source for the atomic bomb.

In June of 1940, President Roosevelt creates the National Defense Research Committee (NDRC). He placed Vannevar Bush in charge and they merge the uranium committee within the NDRC. The budget was increased to $40,000 which is equivalent to $734,000 in today’s dollars.

On February 25th, 1941, Plutonium was discovered by Glenn Seaborg and Arthur Wahl at the University of California, Berkely. This would prove useful for the 2nd atomic bomb to be dropped on Nagasaki, Japan.

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Enter the Manhattan Project

On December 7th, 1941, Japan attacked Pearl Harbor in Honolulu, Hawaii. President Roosevelt stated it was “a date which will live in infamy”. World War 2 had started on September 1st, 1939 and due to the attack on Pearl Harbor, the United States officially entered the war on December 7th, 1941. So, on December 8th, 1941, the United States and Britain declare war on Japan. On December 11th, Germany and Italy declare war on the United States and the United States responds the same day, declaring war on Germany and Italy. What a roller coaster ride, right?

On January 19th, 1942, President Roosevelt authorizes the atomic bomb project, which would be named the Manhattan Project. The United States Army Corps of Engineers is placed in charge of the project and the Manhattan Engineering District has delegated responsibility for the project. Recently promoted Brigadier General (BG) Leslie Groves would be made the director of the project.

Four locations become important to the creation of the atomic bomb, Oak Ridge, Tennessee, Los Alamos, New Mexico, Chicago, Illinois, and Hanford, Washington.

On September 29th, 1942, Under Secretary of War, Robert Patterson authorized the Corps of Engineers to purchase 56,000 acres in Oak Ridge, Tennessee. Oak Ridge, TN would be the location where numerous giant spectrometers would be built to separate isotopes from uranium. This would allow them to extract uranium 235, which was needed for the first atomic bomb named “Little Boy”. Note, gaseous diffusion was discovered to be much easier than using spectrometers and would later be the main method for extracting uranium 235. Stone and Webster an engineering services company was placed in charge to build the massive site in Oak Ridge, TN. A did you know fact about this, because of the requirement for so many large spectrometers to be built, it required thousands of workers. This led to Oak Ridge, TN being the 5th largest city in Tennessee.

Oppenheimer and Groves at Atomic Bomb Test Site.

BG Groves places J. Robert Oppenheimer in charge of the site at Los Alamos, New Mexico on October, 19th, 1942 and he would be primarily in charge of Bomb Design. Mr. Oppenheimer was a physicist and professor at the University of California, Berkeley. He was known as a very temperamental person and many were surprised by this choice. BG Groves had a way of picking the right people for the job and this proved to be no different.

On December 2nd, 1942, Enrico Fermi built the first nuclear reactor at the University of Chicago. Enrico Fermi successfully tested a self-sustaining nuclear reaction. What was crazy about this, it was done in a heavily populated area within Chicago, Illinois, but Mr. Fermi was given the go-ahead to conduct the test. Luckily everything he did was done right and there were no runaway reactions.

On February 9th, 1943, Under Secretary of the Army Patterson approved 400,000 acres to be purchased in Hanford, Washington. This would be the site where plutonium would be produced in large quantities. The plutonium from the Hanford site would be used for the first-ever atomic bomb test as well as the bomb dropped on Nagasaki, Japan named “Fat Boy”. Based on my reading about this particular site, nuclear waste was not properly dealt with and unfortunately is an issue for the surrounding areas, even today.

Between August and December of 1943, both the United Kingdom and Canada join the Manhattan Project and allow their scientists to collaborate with those in the United States. This collaboration was called the Combined Policy Committee. The committee consisted of United States Secretary of War Henry Stimson, Vannevar Bush, and James Conant from the United States. The members from the United Kingdom were Field Marshal Sir John Dill and Colonel J.J. Llewellin, the single-member from Canada was C.D. Howe.

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Around late November 1944, it was discovered through some documents that Germany had not made significant progress towards developing an atomic bomb and it was not even a high priority to them any longer.

On December 17th, 1944 the United States stood up the 509th Composite Group formed under Colonel Paul Tibbets to deliver the atomic bomb. Colonel Tibbets and the 509th Composite Group would be stationed on the island of Tinian, which is a small island located 1,500 miles from Japan. A strategic location and the capabilities to modify the B-29 Superfortress bombers to carry the atomic bombs. Colonel Tibbets knew that if and when the day came that they drop the atomic bombs it would be a day known throughout history. This meant he wanted to name his plane something that would be unique, he decided to name the plane after his mother, Enola Gay Tibbets. Major Charles Sweeney was the pilot of the other B-29 Superfortress named “Bockscar”. The plane was named after Captain Frederick Bock, this probably has you wondering why Captain Bock didn’t drop the second atomic bomb. The simple answer is, Major Sweeney had flown more training and practice missions in the plane and the fact that this was a military plane and Captain Bock did not own it. He just had the pleasure of being one of the first to fly the plane and getting to name it.

On April 12th, 1945 President Roosevelt died. President Roosevelt was a chain smoker and was suffering from congestive heart failure. He supposedly had plans to resign after the war ended but would die just short of that date. His Vice-President Harry S. Truman takes over as President. The Manhattan Project was so secret, President Truman knew very little about it. He had to be briefed in-depth about the project. President Truman wrote in his diary on July 25th, 1945 “We have discovered the most terrible bomb in the history of the world. It may be the fire destruction prophesied in the Euphrates Valley Era, after Noah and his fabulous Ark”.

After Germany surrendered on May 7th, 1945, President Truman traveled to Europe for a conference and he hinted to some allies including Soviet leader Joseph Stalin about the atomic bomb, but the Soviets were already aware of the bomb through espionage, they knew about it before he did.

Where was the First Atomic Bomb Tested

President Truman was still in Europe on July 16th, 1945 when the first-ever successful atomic bomb was detonated. This atomic bomb was plutonium based as uranium 235 was to difficult to extract and could not be wasted. The bomb testing was named the “Trinity nuclear test” and the bomb itself was known as the “gadget”. It was tested at Alamogordo, New Mexico at 5:29 AM. There was a massive ball of fire that went over 40,000 feet into the air and was equivalent to 20,000 tons of (Trinitrotoluene) TNT. The atomic bomb vaporized the steel tower it was dropped from and turned 800 yards of sand into glass. On this same day, the USS Indianapolis was sailing to Tinian with the required nuclear components to be placed on the B-29 Superfortress planes.

Atomic Bombing of Hiroshima, Japan and Nagasaki, Japan

Why Did the United States Drop the Atomic Bomb on Japan

President Truman had a tough decision to make. Would he drop the most destructive bomb known to man and kill thousands of innocent people or would he send in the military to fight the war on the ground as well as drop thousands of bombs on Japan? This would mean thousands of American and allied military would lose their lives as well as innocent civilians. Part of the pressure was, the United States would eventually find out about the atomic bomb and this could blow-up having known the war could be ended with one bomb and no more loss of allied forces lives. The other thing causing problems was worrying about the Soviets causing the Japanese country to be divided into a communist country like Germany where one part of the country is communist and the other is not. A decision had to be made and it was.

Who Dropped the Atomic Bomb

General Carl Spaatz, Commander of the Strategic Air Forces in Europe is ordered on July 25th, 1945, to bomb one of the targets which were Hiroshima, Kokura, Niigata, or Nagasaki as soon as weather permitted after August 3rd, 1945.

On August 6th, 1945, 75 years ago today (August 6th, 2020), the Enola Gay piloted by Colonel Tibbets dropped the first atomic bomb named “Little Boy” on Hiroshima, Japan at 8:15 AM. The atomic bomb was dropped from a height of 31,000 feet and the altimeter on the bomb caused it to detonate at just 1,900 feet above the ground. Little Boy was a gun-type bomb using uranium 235. When it detonated over Hiroshima, the blast and fallout spread over 4 miles. Within seconds, 70,000 people are killed, buildings and people are vaporized.

Three days later on August 9th, 1945, the second and final atomic bomb named “Fat Man” to ever be used in war was dropped on Nagasaki, Japan at 11:02 AM. The B-29 Superfortress named “Bockscar”, piloted by Maj Sweeney dropped the atomic bomb. Fat Man was a plutonium-based atomic bomb and detonated at 1,650 feet above the city. The bomb unleashed the equivalent of 22,000 tons of TNT. This atomic bomb was much more powerful than the bomb dropped on Hiroshima, however, the mountainous region of Nagasaki prevented the further spread of nuclear fallout from the atomic bomb. Where the fallout from the atomic bomb on Hiroshima spread for 4 miles, the one on Nagasaki spread for just over 2 miles.

How Many People were Killed by the Atomic Bombs

It is estimated that over 70,000 people died instantly when the bomb detonated over Hiroshima, Japan. A total estimate of 90,000 to 140,000 people died due to the bombing, which is close to 39% of the total population.
Around 39,000 people died instantly from the atomic bomb on Nagasaki, Japan. A total estimate of 60,000 to 80,000 people died due to the bombing.

It is believed many people continued to die months later due to the atomic bombings on each city and many other diagnoses such as cancer, leukemia, birth defects, and other medical issues were a direct result of the bombings.

How Does the Atomic Bomb Work

The simplest explanation of this without getting too technical is a process called fission. This is the process of hitting a uranium 235 atom at a high speed by a neutron. This causes the uranium 235 atoms to split into two or three new neutrons releasing a massive amount of energy. Scientists also discovered plutonium while learning to extract uranium 235, which was much easier to produce. To make the chain reaction to happen, they need to find a way to prevent the neutrons from escaping and thus being a dud. They found the best shape to contain the neutrons was within a sphere and coat with a mirror that caused the neutrons to deflect and continue the chain reaction. Scientists created a gun like a mechanism within the atomic bomb container that allowed two uranium 235 or plutonium spheres to combine which essentially sets off the atomic bomb after it reaches what is called super-critical mass.

The actual Little Boy atomic bomb used on Hiroshima.

The atomic bomb Little Boy contained 140 pounds of uranium 235 which created an explosion equal to 20,000 tons of TNT.

The atomic bomb Fat Man only needed 14 pounds of plutonium to be more powerful than the uranium filled bomb. It exploded with an explosion equal to 22,000 tons of TNT.

Actual Fat Man atomic bomb used on Nagasaki.

In Conclusion

Genbaku Dome Before Atomic Bomb

Our prayers and condolences go out to all of the friends and families of anyone that lost their lives or were affected by this sad day in history. It ended a long, drawn-out war that resulted in the loss of over 85 million people or 3% of the world population at that time. It was the deadliest war in history and we can only hope we never see such a war again.

Genbaku Dome after the atomic bombing.

Between 1950 and 1964, the Genbaku Dome became part of the Hiroshima Peace Memorial to serve as a memorial to the over 140,000 people who were killed in the atomic bombing of Hiroshima, Japan.

Genbaku Dome part of the Hiroshima Peace Museum.
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