Assessing the Decision to Build and Use the
Atomic Bomb
Col. Paul W. Tibbets, Jr., pilot of the Enola Gay, the plane that dropped the
atomic bomb on Hiroshima, waves from his cockpit before takeoff.
Albert Einstein
Whether to Build an Atomic Bomb
In August 1939, FDR received a letter
from Albert Einstein. He alerted FDR
that Germany might be building an
atomic bomb. When Einstein wrote
this letter to Roosevelt, the US was not
yet at war with Germany. However,
FDR took interest in the developments
described in the letter. The bomb
would not only be the most powerful
weapon on earth, it would transform
warfare by making it possible to kill
more people with less effort.
In the 18 months following Einstein’s letter,
members of the Roosevelt administration
debated what action should be taken to
counter the German threat. Some officials
wondered how serious the threat really
was. In addition, not all scientists agreed
with Einstein. In fact, two Nobel Prizewinning nuclear physicists, Enrico Fermi
and Niels Bohr, believed that the
construction of an atomic bomb was a
practical improbability.
Critical Thinking
Question 1
You are an advisor to President
Roosevelt. Which of the
following do you advise the
president to do? Explain why.
A: Ignore scientific
developments and do not
build an atomic bomb;
concentrate U.S. efforts on
building conventional
weapons, such as faster
planes and more powerful
tanks.
B: Vigorously pursue the
construction of an atomic
bomb because the United
States is in a race against the
Germans.
C: Postpone the development
of an atomic bomb and send
spies into Germany to
determine the accuracy of
Einstein’s letter.
D: Do not develop the bomb.
Instead, monitor the
construction of new German
weapon facilities and then
send American bombers to
destroy them.
E: Denounce the development
of atomic bombs as immoral.
Only evil could come from
their development.
Question 1: Actual Decision
• 1939 – FDR supported bomb research;
discovered a bomb could be built in two
years
• Manhattan Project – code name for top
secret project – Led by Robert
Oppenheimer – 100,000 people involved –
cost $2 billion – Fermi and Bohr major
players in development
• No formal agreement; just understood that
any weapon developed would be used to
end war quickly
J. Robert Oppenheimer
How the Bomb Worked
A sphere of U-235 is made around the neutron
generator and a small bullet of U-235 is removed. The
bullet is placed at the one end of a long tube with
explosives behind it, while the sphere is placed at the
other end. A barometric-pressure sensor determines
the appropriate altitude for detonation and triggers the
following sequence of events:
1. The explosives fire and propel the bullet down the
barrel.
2. The bullet strikes the sphere and generator, initiating
the fission reaction.
3. The fission reaction begins.
4. The bomb explodes.
Simulation: How the “Little Boy” bomb worked
http://people.howstuffworks.com/nuclear-bomb5.htm
How the Bomb Worked, Con’t.
Scientists recognized that compressing the
subcritical masses together into a sphere might
be a good way to make a supercritical mass.
There were problems with this idea. But the
Manhattan Project team solved the problems.
When the bomb was detonated, this is what
happened:
1. The explosives fired, creating a shock wave.
2. The shock wave compressed the core.
3. The fission reaction began.
4. The bomb exploded.
Simulation: How the “Fat Man” bomb worked
http://people.howstuffworks.com/nuclear-bomb6.htm
Workers with the Manhattan Engineer District gently carry the
plutonium core for the world's first atomic bomb into the
McDonald Ranch house for assembly, July 12, 1945
A member of the
Manhattan Project's
Special Engineering
Detachment holds the
assembled plutonium
core for the world's
first atomic bomb in a
special shockabsorbing case on July
12, 1945. The core was
about the size of an
orange and weighed
13.5 pounds.
Physicists Norris Bradbury and Boyce McDaniel stand at the top
of a 100 foot tower after helping to assemble the world's first
atomic bomb on July 15, 1945, one day before the Trinity test.
The device was nicknamed the "Gadget."
Photo of Trinity test site - Ten seconds after detonation
Oppenheimer and Leslie Groves inspect the tower.
Facts about the Bomb’s Test
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Before dawn – July 16, 1945 – “gadget”
tested
Fireball so bright – blind girl saw flash
Cloud rose eight miles into the sky
Force so strong windows shattered in
buildings 125 miles away
Crater left in Earth was 1,200-foot-wide
People were told an ammunition dump
exploded
The sand directly under the tower got so
hot that it turned to glass
More Facts about the Bomb’s Test
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The explosion was equal to 20,000 tons of
TNT
Half mile from the blast: everything was either
vaporized or burned beyond recognition
One Mile from the blast: all buildings above
ground were destroyed
Two miles: structures collapsed and rivers
flowed the wrong way
Three miles away: buildings sustained severe
fire and wind damage, people would have
suffered second and third degree burns, if
they were lucky
Revelation 6:12
And I beheld when he had opened
the sixth seal, and, lo, there was a
great earthquake; and the sun
became black as sackcloth of
hair, and the moon became as
blood.
Harry S. Truman
Vice-president Harry S. Truman taking the oath of office after the death of
FDR. Not until nearly two weeks after he was sworn in was he told about
the existence of the atomic bomb.
Whether to Drop an Atomic Bomb
Vice President Harry S. Truman became
president after Roosevelt unexpectedly died in
April 1945. While attending an Allied
conference in Potsdam, Germany, three
months later, Truman received a telegram
stating that the test of the atomic bomb had
been successful. By this time in the war,
Germany had been utterly defeated. However,
Japan had vowed to fight on, despite the Allies’
demand at Potsdam for an unconditional
surrender. The Japanese felt that an
unconditional surrender would jeopardize the
position of their emperor, whom they
considered divine (Godlike).
In addition, the Japanese viewed surrender as
dishonorable. They fought with fanatic
resistance and believed it was more honorable
to commit suicide than to surrender to enemy
forces. In this vein, Japanese kamikaze pilots
strapped themselves into planes loaded with
explosives and crashed them into American
naval vessels. They managed to destroy 53
ships and damage 158 others. The US had
hoped to end the Pacific War by invading the
home islands of Japan. However, in the face of
Japanese fanaticism, Truman was deeply
concerned that such an invasion would cost
tens of thousands of American lives.
In light of this concern, some of Truman’s
advisors recommended that he end the war
quickly by dropping a bomb without warning
on a large Japanese city. The undersecretary
of the navy, Ralph Bard, disagreed and told
Truman that dropping the bomb without a
specific warning would jeopardize “the
position of the US as a great humanitarian
nation.” A group of scientists from the bomb
project suggested that the US drop the bomb
in a remote, unpopulated location to show the
bomb’s power and convince Japan to
surrender.
Critical Thinking
Question 2
You are a close advisor to
President Truman. Which of the
following do you advise the
president to do? Explain why.
A: Without warning, drop an
atomic bomb on a Japanese
city as soon as possible.
B: Drop the bomb on an
unpopulated area to
demonstrate its destructive
capabilities.
C: Warn the Japanese that the
United States possesses
atomic weapons and is willing
to use them if they don’t
surrender in a specified time.
If they don’t surrender, then
drop the bomb.
D: Reject the use of atomic
weapons, and continue the
naval blockade and
conventional bombing. If the
measures do not produce a
Japanese surrender, invade
Japan.
E: Reject the use of atomic
weapons and negotiate an
end to World War II, allowing
the Japanese to surrender
with their emperor as a part of
the postwar government.
Question 2: Actual Decision
• August 6, 1945 – Enola Gay dropped bomb
on Hiroshima; 100,000 people killed
• August 9, 1945 – bomb dropped on
Nagasaki; 70,000 people killed
• Japan surrendered 5 days later
• Truman defended his decision by saying it
saved the lives of thousands of American
soldiers
Leaflets dropped on cities in Japan - c. August 6, 1945
TO THE JAPANESE PEOPLE:
America asks that you take immediate heed of what we say on this
leaflet.
We are in possession of the most destructive explosive ever devised
by man. A single one of our newly developed atomic bombs is
actually the equivalent in explosive power to what 2000 of our
giant B-29s can carry on a single mission. This awful fact is one for
you to ponder and we solemnly assure you it is grimly accurate.
We have just begun to use this weapon against your homeland. If
you still have any doubt, make inquiry as to what happened to
Hiroshima when just one atomic bomb fell on that city.
Before using this bomb to destroy every resource of the military by
which they are prolonging this useless war, we ask that you now
petition the Emperor to end the war. Our president has outlined for
you the thirteen consequences of an honorable surrender. We urge
that you accept these consequences and begin the work of building
a new, better and peace-loving Japan.
You should take steps now to cease military resistance. Otherwise,
we shall resolutely employ this bomb and all our other superior
weapons to promptly and forcefully end the war.
EVACUATE YOUR CITIES.
ATTENTION JAPANESE PEOPLE. EVACUATE YOUR CITIES.
Because your military leaders have rejected the thirteen part surrender
declaration, two momentous events have occurred in the last few days.
The Soviet Union, because of this rejection on the part of the military has
notified your Ambassador Sato that it has declared war on your nation.
Thus, all powerful countries of the world are now at war with you.
Also, because of your leaders' refusal to accept the surrender declaration
that would enable Japan to honorably end this useless war, we have
employed our atomic bomb.
A single one of our newly developed atomic bombs is actually the equivalent
in explosive power to what 2000 of our giant B-29s could have carried on
a single mission. Radio Tokyo has told you that with the first use of this
weapon of total destruction, Hiroshima was virtually destroyed.
Before we use this bomb again and again to destroy every resource of the
military by which they are prolonging this useless war, petition the
emperor now to end the war. Our president has outlined for you the
thirteen consequences of an honorable surrender. We urge that you
accept these consequences and begin the work of building a new, better,
and peace-loving Japan.
Act at once or we shall resolutely employ this bomb and all our other
superior weapons to promptly and forcefully end the war.
EVACUATE YOUR CITIES.
Hiroshima, August 6, 1945
Nagasaki, August 9, 1945
Facts about the Bomb in Japan
• Temperature at the center of blast – 100
million degrees
• People at the center vaporized – remains
left shadows on pavement and walls
• Skin was seen peeling and hanging off of
bodies
• Many died of radiation poisoning – lost their
hair, vomited blood, then died
Whether Truman Made the Right Decision
Immediately following the dropping of the two atomic
bombs on Japan, the majority of Americans felt the right
decision had been made. Surveys conducted by
Fortune magazine in the fall of 1945 revealed that over
50% of Americans believed that the US “should have
used the two bombs on cities just as we did.” Another
22.7% felt the US “should have quickly used many more
before Japan had the chance to surrender.” American
soldiers also supported Truman’s decision. One young
soldier stated: “When the bombs were dropped and
news began to circulate that the invasion would not take
place after all, that we would not be obliged to run up the
beaches near Tokyo assault-firing while being mortared
and shelled…we cried with relief and joy. We were
going to live. We were going to grow up to adulthood
after all.”
Many officials in the top ranks of the military and
government supported Truman’s decision to
drop the atomic bombs. However, others
expressed doubts. Admiral William D. Leahy
stated: “It is my opinion that the use of the
barbarous weapon was of no material
assistance in our war against Japan. The
Japanese were all ready defeated and ready to
surrender because of the effective sea
blockade and the successful bombing with
conventional weapons. My own feeling was
that being the first to use the bomb, we adopted
an ethical standard common to the barbarians
of the Dark Ages.”
Dwight D. Eisenhower, a general with enormous
prestige, expressed the hope that the US would
never have to use such a weapon against an
enemy again because he disliked seeing the
country “initiate the use of anything so horrible
and destructive.” Some historians have severely
criticized Truman’s decision. They argue that the
Japanese were all ready defeated in August
1945, and that the atomic bombs were used
primarily as a warning to the Soviet Union.
Although they were allies during WWII, the US
and the USSR had very different visions for the
postwar world.
Historians critical of Truman’s decision argue that
he authorized the use of the atomic bombs
mainly to scare the Soviets out of Eastern
Europe and to keep them from gaining more
territory in Asia. To these historians, the
citizens of Hiroshima and Nagasaki were
sacrificed in a high-stakes poker game between
two superpowers. They also argue that the
postwar nuclear arms race can be traced back
to the fear and mistrust created by Truman’s
decision. Other historians counter that the
military pressures Truman was under at the end
of WWII played a much more important role in
his decision than the threat of Soviet
aggression.
Critical Thinking
Question 3
Truman’s decision to use atomic
weapons against Japan is one of
the most controversial in history. In
retrospect, do you think Truman
made the right decision in
authorizing the use of atomic
weapons? Explain why.
A: Truman did not make the
right decision when he
authorized the use of atomic
weapons.
B: Truman made the right
decision when he authorized
the use of atomic weapons.
Question 3: The Debate Continues
• Truman defended his decision to his death.
• J. Robert Oppenheimer, the lead scientist
of the Manhattan Project, said: “I am death,
the destroyer of worlds.”
• Albert Einstein regretted ever writing FDR.
• By 1990 – approximately 100,000 nuclear
weapons in existence
“Fat Man” and “Little Boy”
Located just under the hypocenter, only the domeshaped framework and part of the outer wall remained. It
has come to be called "the A-bomb Dome."
August 6. 1945. This is one of six photographs
recording the disaster of Hiroshima.
The cause of keloids is not clear yet, but it is
considered to be caused by a combination of
powerful heat rays and radiation.
The dark portion of the pattern of the clothing was
imprinted on the skin by the powerful heat rays.
A person sat down on the steps facing the direction of the
hypocenter, possibly waiting for the bank to open. By a flash of
the heat rays, that person was incinerated on the stone steps.
A woman who was exposed to the A-bomb less than
2 kilometers from the hypocenter, judging by the
extent of the burns on her entire back.
Close to the hypocenter, victims were burned to
death in their last gesture grasping at the air or trying
to escape.
This boy had thermal burns on more than onethird of his body. He miraculously recovered.
A child crying from the pain of having a gauze dressing
changed. He suffered third-degree burns that exposed
the bone.
A view of Nagasaki after the explosion
A shadow made by the heat rays. This place is about 800
meters from the hypocenter. The unshielded asphalt surface
was scorched, and the surface shielded by the handrail is a
whitish shadow.
This boy was burned to death with his hands placed
on his chest, leaving an impression of agony.
Critical Thinking
Question 3
Truman’s decision to use atomic
weapons against Japan is one of
the most controversial in history. In
retrospect, do you think Truman
made the right decision in
authorizing the use of atomic
weapons? Explain why.
A: Truman did not make the
right decision when he
authorized the use of atomic
weapons.
B: Truman made the right
decision when he authorized
the use of atomic weapons.
Nuclear Testing After WWII