Original subtitles

80 years ago, a terrifying power was unleashed -

two nuclear bombs detonated over Japan.

This was the most extraordinary tampering with

the basic fabric of the universe.

Physicists from Britain and America pooled their expertise

in a daring scientific mission,

codenamed The Manhattan Project.

Places that had never, ever existed before,

using technologies that had never, ever existed before,

basically sprang out of the mud.

Thousands of black and white photographs and hundreds of reels

of film survive from those game-changing years.

Now, using the latest technology to transform rarely seen images

and restore, sharpen and repair priceless damaged film,

the Manhattan Project comes to life.

The work of Robert Oppenheimer's team was a turning point in history.

Mankind had acquired the means of its own destruction.

There was a flash of a whiteness.

Within few seconds, turned into pitch dark.

Because I was inside the mushroom cloud.

The genie is out of the bottle, and is not going back in.

March, 1940.

Britain is bracing itself for a German invasion,

and a wave of terror from the skies.

The idea of aerial bombardment terrorising civilian populations

becomes this huge concern in the 1930s.

The Spanish Civil War,

Hitler's invasion of Poland in September '39.

Those show just how deadly bombs can be.

And so, in March 1940, you have Britain on this really high alert

in the expectation of the Luftwaffe dropping high-explosive bombs,

incendiaries, and that causing utter devastation.

Meanwhile at Birmingham University, two Jewish scientists

who fled Nazi Germany - Rudolf Peierls and Otto Frisch -

are exploring the potential of a new type of weapon,

an atomic bomb.

The possibility of a weapon of mass destruction began in Berlin

two years earlier with a revolutionary breakthrough.

German physicists discovered a process known as fission,

the splitting of the atomic nucleus of the uranium atom

into two or more fragments.

So, the question becomes, could you start a chain reaction?

That's why fission is important.

Maybe you could harness this in a non-destructive way

and produce a tremendous amount of electricity.

On the other hand, though, that can be harnessed perhaps

in the form of some sort of weapon as well.

Maybe producing a tremendous amount of energy.

Many scientists believed an atomic weapon would be too large

for any bomber, as it needed to be made of hundreds of tonnes

of uranium-235.

In Birmingham, Rudolf Peierls and Otto Frisch tested that idea,

and made a stunning discovery.

They shocked and amazed, and distressed themselves,

to discover, really, you'd only need a piece of U235 the size

maybe of a melon,

and then you've got yourself a super bomb.

It would liberate as much energy as a thousand tonnes of dynamite.

And it would also liberate radiation, and do damage that way.

And here, at least in theory,

was the possibility of changing the war

and winning the war.

Unless - and this was the moment of horror -

the Nazis were already doing this.

As emigres, Frisch and Peierls knew at first hand

the threat Germany posed.

They urgently wrote up their findings in a memorandum

which they sent to the British government.

As a weapon, the super bomb would be practically irresistible.

There is no material or structure that could expect

to resist the force of explosion.

Owing to the spreading of radioactive substances

in the wind, the bomb could probably not be used without killing

large numbers of civilians.

If one works on the assumption that Germany is, or will be,

in the possession of this weapon, it must be realised that

no shelters are available that would be effective.

The most effective reply would be a counter threat

with a similar bomb.

Therefore, it seems to us to start production as soon as possible.

The British government agreed with scientists Frisch and Peierls,

and launched a research programme to beat the Nazis

to an atomic bomb.

In September 1941, Prime Minister Winston Churchill

gave the green light to an atomic programme, codenamed Tube Alloys.

Remember that Churchill is a Victorian.

He's, really, a 19th century cavalry officer.

He's trained in horse and lance and sword.

And yet, 50 years on from when he took part in the last great

cavalry charge, he's being asked to get his head round a weapon

that is fuelled by the same power source that makes the stars

of the night sky twinkle.

It's quite something.

But within a year, the Tube Alloys project concluded that Britain

was in no position to successfully build a bomb on its own.

The scale of doing it industrially would be vast.

And the possibility of doing this in Britain, which was still under

threat of invasion and regular attack by the Luftwaffe,

was out of the question.

The British looked to the United States for assistance,

because after the Japanese attack on Pearl Harbor, in December 1941,

the Americans had accelerated their own atomic project.

The United Kingdom and the United States joined forces.

The UK became kind of the junior partner,

and sent a couple dozen of its best scientists,

including continental refugees, to the United States.

Britain was expert in the theory of nuclear weapons,

but the Americans were far ahead experimentally.

A key step in the development of an atomic bomb

was to build a nuclear reactor

to prove a controlled chain reaction was possible.

If you can produce a controlled nuclear chain reaction,

you can produce an uncontrolled nuclear chain reaction.

An uncontrolled nuclear reaction being some form of weapon.

In December 1942, in the unlikely setting of a squash court

under a disused stadium at the University of Chicago,

the world's first nuclear reactor took shape.

In the early days of nuclear technology,

safety was not a priority.

Uranium dust was as common on us as sand at a beach.

We were breathing the uranium fumes from the grinding wheels

and from the saws, etc.

We even carried it around in our lab coat pockets.

You could dust it off your coat, like that.

In charge of the nuclear reactor project

was Italian physicist Enrico Fermi.

He was very much sort of hands-on physicist.

He'd previously been doing a lot of work with flow neutrons in Italy,

and had been awarded the Nobel Prize for that work.

So, he was kind of like the main person who knew

about how to do this.

Fermi supervised the building of a six metre-high reactor

made of graphite blocks and uranium rods,

which became known as the Chicago Pile.

On December 2, the reactor was ready

and ran successfully for 4.5 minutes before Fermi shut it down.

He'd created the world's first artificially controlled

nuclear chain reaction.

It was monumental, but nothing visible.

The code word for the experiment being a success was

"The Italian navigator has landed in the New World."

If the pile in Chicago hadn't worked,

there wouldn't have been a Manhattan Project.

Up until the moment that Fermi's experiment was done,

everything had been in theory.

That is the real moment when the atomic age began.

In December 1942, President Roosevelt authorised a huge sum

of $500 million - over $10 billion today -

for an atomic programme to help win the war.

He wants to push this thing now with all speed.

And so, in many ways, the countdown to Hiroshima and Nagasaki

really begins in December 1942.

At the end of 1942,

the Allies were beleaguered and fighting on multiple fronts.

The need to build an atomic bomb was more important than ever.

It's truly a world war,

because you've got conflict in Russia,

you've got the battle of the Atlantic,

you've got the North African campaign,

you've got the Pacific theatre.

And then, you've got to think about the very brutality

of the Nazi and Japanese regimes.

You've got to beat them.

But the whole idea of that seems like a really distant hope.

After the success of the Chicago nuclear reactor,

the Americans began planning two types of bomb,

uranium and plutonium.

The challenge was to enrich these elements in significant quantities

to provide fuel for the bombs.

You are going to need huge factories,

huge workforces to run those factories,

huge workforces to construct them.

So, what entity is good at huge national construction projects?

The Army Corps of Engineers.

The Army Corps of Engineers traditionally named a project

after the location of its headquarters.

For the atomic programme, it was Manhattan.

So, it became known as the Manhattan Engineer District,

later shortened to the Manhattan Project.

The man in charge was Brigadier General Leslie Groves.

General Leslie Groves got things done.

He was responsible for the construction of this

enormous building called the Pentagon.

He had the engineering background.

He certainly had the leadership skills.

He was very no nonsense.

Groves appointed a professor from Berkeley named J Robert Oppenheimer

to oversee the bomb design.

Oppenheimer was a very clever physicist

who had worked on quantum mechanics.

He was not a Nobel Prize winner,

and for Groves, I think, that was one of the key things.

Groves was surrounded by all these Nobel Prize winners,

which probably was overpowering.

And in Oppenheimer, he found somebody that he could talk to,

who would respect him and he would respect them.

Two people of quite different temperaments, they fitted together.

Oppenheimer was a quick learner not only within the realm

of science, but also in the realm of leadership and management as well.

But Oppenheimer could be intimidating, cruel,

awkward, inspiring, absolutely inspiring.

All of these things.

In early 1943, General Groves bought a stretch of land near Hanford,

in Washington State, to build factories to produce plutonium

and entire valleys in Oak Ridge, Tennessee,

for a site to enrich uranium.

Oak Ridge did not exist before World War II.

This was a purpose-built city.

These giant factories, places that had never, ever existed before,

using technologies that had never, ever existed before,

basically sprang out of the mud.

With the war fuelling paranoia about Japanese and Nazi spies,

secrecy was of paramount importance to the Manhattan Project.

Philip Anderson was eight years old when his father was put in charge

of constructing houses at Oak Ridge.

The family were not allowed to tell anyone where they were moving to,

but Philip's school teacher insisted on finding out.

She got right in my face and said,

"You tell me where you're going, and you tell me now."

And I started crying.

And she said - she was right in my face - and she said, "Tell me!"

And I said, "We're going to Oak Ridge, Tennessee."

And she said, "All right."

And I went home that night in tears and told my father what I had done.

And he said, "That's all right. We'll take care of it."

The next morning, agents in coats and hats arrived at the school

and escorted Philip's teacher out of the class.

And when they returned, my teacher was an absolute wreck.

Her hair was dishevelled, she had been crying.

She pulled herself together, and said, "Philip, I'm sorry for what

"I did, and this will just all be a secret between us now,

"just between us, OK?"

I think it demonstrates the secrecy in which Oak Ridge was planned

and developed, and carried on its mission.

Oak Ridge grew to become home to 75,000 residents,

and consumed more electricity than New York City.

Photographer Ed Westcott was employed by the War Department

to record the everyday life of this brand-new city.

His job was to visually document everything that went on.

This could be General Groves - kind of the top brass, so to speak -

but also daily life.

He took pictures of people at the butcher's shop,

pictures at dances, pictures at the bowling alley.

So, it created this incredibly rich look at this

very, very specific, unique moment in history.

Thousands of women made up the Oak Ridge community.

Ruth Huddleston joined when she was just 18.

Her job was to operate electromagnetic separation units,

known as calutrons.

If it went over too far to the right,

we had to adjust it.

Sometimes you had to shut it down.

But we weren't supposed to tell anybody that we operated those.

I don't remember ever even saying, "I wonder what we're doing?"

For a lot of the young people living and working there,

it was a very sociable, exciting experience.

In many ways, it resembled the college experience

a lot of these young women would never have had.

For some of the Oak Ridge community, life was very different.

The city - like all Manhattan Project sites - was segregated.

Black married couples were not allowed to bring children with them,

and they were also not allowed to live together.

There were schools in Oak Ridge,

but there were no schools for the black children.

Ed Westcott's photos capture scenes of a workforce,

black and white, that had no idea they were helping build

a weapon of mass destruction.

It's as though you're watching a film, and you know what's

coming up next, but you can see these characters have no idea

where this is headed.

As well as Oak Ridge and Hanford,

the Manhattan Project needed a third site,

a laboratory to build the bomb away from prying eyes.

Scientific director Robert Oppenheimer loved New Mexico,

and decided that a remote boys' school in Los Alamos

would provide a basic infrastructure.

One of the school buildings became a home for Oppenheimer and his family.

Having looked at photographs of Oppenheimer entertaining guests

in this room, you can almost hear the conversations.

You can almost smell the cigarette smoke, in a sense,

when you really think about it and put yourself in that place.

There are famous photographs of Oppenheimer sitting just behind

where I'm seated right now.

It's almost like a time machine to be able to come into a place

like this, as it was back then,

and to reflect on the laughs that were shared,

the concerns about what nuclear technology might mean

for the future of humanity, those discussions.

It all happened here.

By 1944, all three main Manhattan Project sites were operational.

Los Alamos was receiving plutonium from the massive factories

at Hanford and enriched uranium from the atomic city of Oak Ridge.

Billboards reminded the workers of the urgency of their task.

Thousands of Allied troops were being killed in the war

against Germany and Japan.

We now know that in 1944 the end of the war was effectively

just around the corner - but, of course, nobody knew then.

So, what this poster is trying to do is to inculcate a kind of

sense of urgency in people.

"Look, you've got to do what you can, make every minute count.

"Because even if you're not being bombed in the middle of Tennessee,

"you might lose your son.

"So, the quicker we get on with this, the quicker it ends."

Oppenheimer and his team were attempting to use

revolutionary science to defeat the enemy.

Everything had to be invented from scratch,

and then produced at a massive industrial scale

in order to win the war.

The Second World War is not just fought on battlefields.

It's also fought in laboratories.

Almost every part of the atomic process was unknown and untested.

The stakes are pretty high.

At Los Alamos, the scientists worked six long days a week.

21 came from Britain, including Rudolf Peierls and Otto Frisch,

whose influential memorandum had made the Manhattan Project possible.

Home movies taken by American physicist Hugh Bradner

shows his colleagues making the most what little free time they had.

You'll see them hiking, horseback riding.

Doing all of these activities that are just kind of normal.

It's an incredible view into wartime Los Alamos.

I've never understood how these films were able to come into

existence, because of the rigorous security,

but apparently this was approved.

The British scientists and their families were well known

for holding parties, and even pantomimes at Christmas.

My aunt and my dad really enjoyed their time in Los Alamos.

They had no idea what was going on.

My grandmother had no idea.

Obviously, locals would be curious what was happening up at Los Alamos.

They would try and plant stories to try and keep things secret.

My aunt and my dad recall being told that they trying to

make windscreen wipers for submarines there.

The success of D-Day, and the slow but steady Allied advance

towards Germany, meant that by early 1945 the Nazi threat was receding.

But the threat from Japan remained,

so the Manhattan Project continued without a pause.

By that point, the war in Europe was almost over.

But the Allied bomb was almost complete.

So, the question was, where would they use it?

Japan was an obvious target.

Two entirely different types of bomb were being developed.

One used enriched uranium,

the other plutonium.

Having a choice increased the chance of a successful detonation.

Oppenheimer and his team were almost certain that the uranium bomb

would work - but the plutonium bomb caused concern.

The problems were that plutonium was so delicate that it had a habit

of sort of exploding prematurely,

leading to a fizzle rather than an explosion.

And that's why they had to actually make a bomb and test it.

On May 8, 1945,

as preparations were made to detonate the plutonium device,

Germany surrendered.

Japan fought on.

Although the Japanese were now the target, the Americans and

the British desperately wanted to find out just how far

German nuclear scientists had got with their plans to build a bomb.

In April and May, 1945, Anglo-American forces moving

deep into Germany are on the lookout for evidence

of German nuclear activity.

And on the eastern edge of the Black Forest,

they find what they have been looking for.

They find a lot of paperwork, a lot of secrets,

but, more importantly, they find some German scientists.

Including Werner Heisenberg,

arguably the leading physicist of his generation in Germany,

and also Otto Hahn, who in 1938 was part of the team

that first discovered in their laboratory this process

called nuclear fission.

The ten scientists were brought here to Farm Hall in the UK,

an 18th century house in the heart of Cambridgeshire.

British intelligence had made special plans for their arrival.

Professor Marcial Echenique bought Farm Hall in the late 1970s,

and began updating the electrics.

During that period we start to lift the floorboards.

And we discovered these loose wires which didn't connect to lights

or plugs, or anything like that.

Loads around different rooms in the house.

So, we were very, very puzzled about that.

Marcial discovered the wires were part of an operation,

codenamed Epsilon, which used hidden microphones to listen in

on the German scientists' conversations.

The British thought eavesdropping would be a more successful way

to learn nuclear secrets than interrogation.

The day the scientists arrived,

the intelligence services started recording.

The transcripts of their conversations

are no longer top secret.

What we can see is that, at one point,

one of them gets really very close to working out the truth

about the secret bugging.

"I wonder whether there are any microphones installed here?"

And it's Heisenberg himself who replies, "Microphones installed?"

And then the transcript says he's laughing.

"No, they're not as cute as all that.

"I don't think they know the real Gestapo methods.

"They're a bit old-fashioned in that respect."

Well, of course, Heisenberg was dead wrong.

The British patiently waited,

hoping for insights into the German nuclear programme.

Back in Los Alamos, the testing of the plutonium bomb,

nicknamed the Gadget, was scheduled for mid-July.

A site for the so-called Trinity test had been found in the desert

at the Alamogordo Bombing Range, in New Mexico,

and a 30-metre tower constructed to house the bomb.

On July 13, it was almost ready.

One of Robert Oppenheimer's team filmed the final preparations.

As the Gadget's being prepared in this improvised tent at the base

of the tower, you'll see several scientists who are milling about.

You can tell who Oppenheimer is because of the classic silhouette

that includes his hat which he was famous for.

Everything about this process was new.

The scientists often improvised.

A strip of sticky tape is handed to physicist Norris Bradbury,

who uses it to secure a block of explosives.

The following morning, the bomb was hoisted to the top of the tower.

On the exterior of the bomb case,

you will see this white tape all over it,

and that white tape is covering up holes,

because you want to make sure that you keep the dust in the air

out of those holes, which could affect electrical components

and things like that.

Once atop the tower, the tape is removed.

Everything's wired together.

And at that point, you are getting pretty close

to being able to set it off.

Darkness fell, and Oppenheimer and his team took up their positions

9,000 metres away.

To protect themselves from the blast, some applied suntan lotion

to their faces and arms.

Everyone was on edge.

Was it all going to be worth it?

Building these cities, enriching this product.

Was the Gadget actually going to work?

Or was it going to basically wipe the United States off the map?

At 5.29am,

the world's first atomic bomb exploded.

This was the most extraordinary tampering with

the basic fabric of the universe.

Otto Frisch - who predicted the devastating consequences

of an atomic bomb - watched in awe.

Three decades later, he said that he could still hear

the sound of the blast.

For the first time, many of the other Manhattan Project scientists

realised the magnitude of what they had created.

Oppenheimer was very well read,

and he quoted the Hindu scriptures.

"Now I am become death, the destroyer of worlds."

Somebody else more prosaically said, "Now we are all sons of bitches."

And from that moment on, the conflicts about the morality

of it all became very prominent.

Henry Linschitz, part of the Los Alamos team,

he looked at that broiling mushroom cloud,

and he simply said, "My God.

"We're going to drop that on a city?"

Rachel Fermi knew little about her grandfather Enrico's crucial work

on the Manhattan Project

until her aunt showed her a box of family photos.

Just loose and amongst it was this small sort of faded red snapshot

of a mushroom cloud,

and it was just so shocking to see that there.

That juxtaposition of this icon of kind of mass destruction

within my own family's pictures.

Rachel discovered that it had been taken by technician Jack Aeby,

who gave a copy to her grandfather.

Even though hundreds of cameras were set up to record the test,

Aeby's picture is the only one in colour.

He knew that it was going to be brighter than any light

that had been seen on the earth,

like, apparently ten times brighter than the sun.

And so he used the chair he had to sit on as a kind of tripod

to keep the camera steady.

He took four shots, where he had just guessed the exposure,

and this one worked.

It almost tells the story of the Trinity test in a single picture.

It's so small and fragile, and starting to fade.

It's just the fragility of it, and yet the utterly intense power

that it unleashed at the same time.

As the results of the Trinity test were assessed,

out in the Pacific, the heavy cruiser, USS Indianapolis,

was sailing west.

On board, guarded 24 hours a day, was a second bomb,

codenamed Little Boy.

Its ultimate destination - Japan.

The Trinity test, the detonation of

the world's first atomic bomb had been successful.

When they thought it was safe,

General Groves and Robert Oppenheimer returned to Ground Zero.

The 30-metre-high steel tower had been vapourised,

and the ground turned jade green.

The sand and earth has just been completely fused by

the immense temperature. The atomic explosion itself generates

a temperature hotter than the heart of the sun.

The site had been chosen for its isolation,

but half a million people lived within a 240km radius,

most of them Hispanic or Indigenous Americans.

Bernice Gutierrez was born eight days before the test.

She and her parents lived just 55km away in the village of Carrizozo.

Neighbours felt the force of the blast.

RUMBLING EXPLOSION

They describe it as brighter than the sun.

They experienced falling out of bed.

They experienced windows cracking.

The animals that were outside facing the radiation

turned white.

The Manhattan Project bought some of the livestock

to study the effects of radiation,

but didn't collect data about civilian exposure,

concerned it would alarm the public.

Over the decades, Bernice's family have been devastated by cancer,

including her mother, sister and two brothers.

Of my three children,

my oldest son became sick with a precursor to leukaemia,

and he passed away from that four years ago.

My husband survived colon cancer

and now has been diagnosed with prostate cancer.

My only daughter survived thyroid cancer.

And so far, so good,

my youngest son so far hasn't had anything,

but in my family,

we don't ever ask if we're ever going to get cancer.

We wonder when. You never know...

Excuse me.

You never know who's going to be next.

The first victims of nuclear radiation were not Japanese,

but American.

Bernice is part of a group who call themselves Downwinders,

campaigning for compensation

and an acknowledgement

of what's happened to them and their families.

What the government did to us,

they poisoned us and never came back.

We were expendable, disposable people.

On 26th July 1945,

the uranium bomb Little Boy arrived on

the Pacific Island of Tinian.

That same day President Harry Truman called

for Japan's unconditional surrender.

When they refused,

Truman authorised the use of the atomic bomb.

He knows that he's going to lose

maybe half a million American lives taking Japan.

He also knows that maybe millions of Japanese will die.

But if he drops the A-bomb, in a split second,

yes, he'll kill tens of thousands of Japanese,

but that may be fewer lives lost than an attritional campaign

to take the whole of the Japanese homeland.

The target was Hiroshima,

chosen as it was largely untouched by bombing raids.

The effect of the new weapon could therefore be more easily measured.

On August 5th, Little Boy was loaded into a brand-new B-29 bomber.

The pilot, Paul Tibbets,

then had his mother's name painted in its side - Enola Gay.

It took off in the early hours of August 6th.

The bomb is primed in the air, and at that point,

Paul Tibbets tells the rest of the crew

that they're gonna be making history,

that they're carrying an atomic bomb.

It's gonna be the first combat use of this weapon.

Ten-year-old Hideko Tamura is living

with her family close to the centre of Hiroshima.

She has just returned to the city having been evacuated

to the countryside.

On the morning of August 6th,

Hideko woke early.

I'm so happy I'm home, with all my books

and all my everything.

It was the happiest, ultimate happy moment.

It's a beautiful day.

It is a clear blue sky

and into that sky will come a single bomber, the Enola Gay.

At 8.15, the bomb doors open, and Little Boy is released.

45 seconds later it detonates.

It started with a flash of a whiteness,

followed almost instantly was the humongous explosion.

Within a few seconds, it turned into pitch dark.

That was because I was inside the mushroom cloud.

I remember saying to myself, "So this is dying in the war."

Hideko somehow survives under the rubble of her home.

She's not the only member of her family still alive.

From the rear entrance

staggered in my father's older brother, Uncle Hisao,

covered with blood.

In the middle of his throat

was a great big piece of glass.

He said, "Mo dameda."

It's the end of everything, end of life.

Although her uncle and aunts survive,

Hideko's parents are missing.

Her cousin Hideyuki is killed.

He was obsessed with American B-29 bombers.

Hideko can guess his final moments.

So, when B-29 Enola Gay came, just before it dropped,

he must have said, "Oh, B-29!"

I can't stand it, thinking about it, picturing that.

It breaks my heart in a thousand pieces...

..even today, 80 years since.

Most people had multiple life-ending injuries,

and these were caused generally by burns, horrific burns,

and also as a result of injuries sustained from blast damage.

Many people also receive significant doses of radiation.

I lost my hair

and ran high fever that went past the thermometer.

It was physically a very trying time.

And then suddenly my father is there,

and he said I have to take hold of myself.

I have to want to live because he wanted me to live.

Hideko recovered from the radiation sickness.

Soon after, her mother's remains

were found in the rubble of the city.

In 1952, Hideko moved to the United States

and became a lifelong campaigner for peace and reconciliation.

The day after Hiroshima was bombed,

the workers at Hanford and Oak Ridge finally learned

the secret of what they had been making.

The first thing I thought was,

"My boyfriend will be home."

And then I got to thinking -

they start telling all the people that were killed over there.

And it made you think of something else,

you know, that I had a part in it,

cos that's what they told us.

I didn't much like the idea that I had a part in it.

But war's war.

Ain't nothing you can do about it but try to stop it.

On the day Hiroshima was bombed, at Farm Hall in England,

the ten German scientists who were being secretly recorded

to uncover their nuclear secrets,

were told by the British about the atomic strike.

Some of them are seriously distraught at this news.

And what the transcripts show is that you have

the physicist Walther Gerlach - he goes immediately up to his bedroom

and what the hidden microphones pick up

are the sounds of him sobbing.

He's then followed up there by his colleague Otto Hahn.

And Hahn asks him,

"Are you upset because we did not make the uranium bomb?

"I thank God on my bended knee that we never made it."

"Or are you depressed because the Americans

"could do it better than we could?"

Gerlach then replies, yeah, that is the reason for him crying.

It seemed to the intelligence officers listening in,

that the Germans had been far behind

the Manhattan Project in atomic bomb technology.

Otto Hahn declares,

"They are 50 years further advanced than we are."

In Washington, with no sign of a Japanese surrender,

President Truman authorised the dropping of a second,

more powerful device, codenamed Fat Man.

Kokura was target number one, Nagasaki was the backup.

Weather conditions on 9th August were bad at Kokura,

and therefore, Nagasaki was promoted to number one target that day.

The B-29, nicknamed Bockscar, dropped Fat Man

just after 11am on August 9th.

Little Boy's explosive uranium power

was the equivalent of 15,000 tonnes of TNT.

The plutonium Fat Man was

the equivalent of 21,000 tonnes.

It landed off target,

but its destructive power was immense.

What the blast didn't destroy, a firestorm finished off.

It's estimated the total number of dead in Hiroshima

and Nagasaki was over 200,000.

Six days later, on August 15th, Japan surrendered.

The war was over.

The Manhattan Project had achieved its aim.

General Grove's mission statement was to be able

to build and deliver a working atomic weapon

before the enemy. He succeeded.

The Manhattan Project officially ended on January 1st 1947.

Many of the Los Alamos scientists returned to university life.

Some were troubled by what they had done.

Robert Oppenheimer became a key figure in

the debate about atomic weapons.

He believed bombing Japan was the best option to end the war,

but the lives lost weighed heavily on his mind

for the rest of his life.

It wasn't just a city, it wasn't just the enemy,

these were humans, and there was a very high human cost

that was paid as a result of the attacks.

I believe when you become scientists,

you are not seeking to make human life miserable.

You have a goal generally open

to enhance the quality of human life.

How can any serious scientist come to do this?

80 years on,

debate around the morality of the Manhattan Project continues.

What is undisputed is that it

changed the course of human history.

We continue to grapple with

the effects of the development of nuclear weapons

and nuclear energy to this very day.

Perhaps the further that Hiroshima and Nagasaki recede into the past,

the more they become history,

the more they become forgotten about.

The memory of Hiroshima and Nagasaki

as a bar to the use of nuclear weapons,

that begins to erode.

And that is a really, really worrying and dangerous thought.

And that in turn, is why we must never forget the impact

of the first and so far only occasion these awful weapons

of mass destruction have been used against human beings.

The genie is out of the bottle and is not going back in.

Subtitles by Red Bee Media