Original subtitles

- [Narrator] Hidden in the middle of a remote forest

in Northern France, the Nazis build a structure

of colossal proportions.

- It's spectacularly huge.

- This is just a giant block of concrete.

- There is no way to hide something of this scale.

- [Narrator] The sheer size and speed

that the construction presents baffles

the watching Allies, who must find out

what the Germans are planning.

- There must be something awfully important going on

inside that facility.

- Something that is not meant to be exposed

to the outside world.

- [Narrator] As the Allies watch,

a secret terror is forming in this building.

- This is a new type of terror.

- It took people's breath away.

- It is an absolute game changer.

- [Narrator] Yet this secret base will guard

its mysteries throughout the war

and even after its capture and inspection.

- The Allies knew that the Nazis were working

on something terrible in these facilities.

- What is hiding inside this building?

[dramatic music]

- [Narrator] The forest of EÉperlecques is dense, high

and set in the valley of a mountain

just west of the small town of Watten.

It's the site of a mysterious structure.

- It just exudes this menace.

- It has that thick, permanent, evil mysterious look.

[speaks foreign language]

- [Narrator] In 1943, an Allied reconnaissance plane

spots the construction of a giant complex

in the EÉperlecques forest in Northern France.

Unbeknownst to them, Hitler has a secret plan,

more terrible than anything the Allies have seen.

And this place is a foundation of the plan.

- The Nazis built a lot of big bunkers,

big structures, but this had to be one of the biggest.

It's literally one of the largest structures

one would ever see.

- It's a big lump of concrete in the middle of nowhere.

What the heck could that possibly have been used for.

- [Narrator] Though Hitler's plans may be ambitious,

he's deliberate about his strategy.

In December, 1942, he sent engineers and officers

on a tour of Northwest France to find the perfect location

for his secrete base.

- The forest chosen for where Blockhouse was

to be constructed is absolutely perfect

for what the Germans want to achieve here.

It's on a railway line.

It's got a Luftwaffe base right near by.

There's a radar station.

It's near a river, so they've got water

for their construction and for cooling

and everything else they might need that for.

But it's far enough away from the sea

so they don't come under the threat from naval guns.

It backs on to a hill to protect it from artillery fire,

and of course is concealed by a forest.

- There is a town nearby, but it's not big enough

for this particular site to raise any kind

of attention or concern.

[speaks foreign language]

- [Narrator] By March, 1943, Hitler has approved the plans

for the site.

His go-to engineering firm, Organization Todt moves in

6,000 workers, all French, Belgium and Dutch-forced labor

to begin the excavations.

- Organization Todt built the Autobon,

the Atlantic Wall, the Siegfried Line

and so many other remarkable engineering structures.

- Hitler ordered that the site be operational

for the 1st of November, 1943, which meant

that they had to build it in less than six months.

The speed is just phenomenal.

- I worked on some projects that were municipal bridges,

two, three-lane bridges, that took years

in the planning and execution of it.

And that's just a small bridge.

That is a tiny, tiny portion of Blockhaus.

There is no scale that can be compared to that.

It's a massive building.

- With everything going wrong for Nazi Germany,

how did the marshal the resources

to build something that big at the end of the war

when everything's imploding.

Where's the money?

Where's the concrete?

Where's the labor coming from?

- Chanling managed to have it ready in just six months.

[dramatic music]

[speaks foreign language]

- This is an astronomical amount of concrete.

- In order to create Blockhaus, the Nazis used

120,000 cubic meters of concrete

that was reinforced with 20,000 tons of steel.

- The reinforcing bars were made off site,

and they would come in large bundles.

Those bars maybe needed to be bent

or cut into different lengths to be able

to create the structure.

They needed to be placed, to build this rebar cage,

and tied together to create a rebar structure.

Then the concrete was poured around that.

- To feed this construction that was so concrete-hungry,

cement mixers were turning and churning out

what was needed, 24 hours a day continuously

during this construction.

[speaks foreign language]

- This is a really tall structure.

They had to pump that liquid concrete up to the top

to be deposited into the forms continuously

as they move across the construction level.

It's not easy.

- The labor force needed to build

a concrete mountain is astronomical.

They used forced labor from concentration camps,

prisoners of war.

The advantage there is you don't have to pay people,

and you can literally work them to death.

- They were working 12-hour shifts

with three to 4,000 men per shift

with only a few 20-minute breaks.

Many workers died on the site.

- [Narrator] In the space of nine months,

about 35,000 people passed through the Kraftwerk Nord site.

- Blockhaus must have been a beehive of activity.

You have trains pulling in around the clock.

You have trucks coming in around the clock.

You have laborers coming around the clock.

And your workforce is literally working around the clock.

- Yeah, the Allied planes overhead looking

down on this are baffled.

They can only speculate, what on earth is this site for?

- [Narrator] Some of Churchill's advisors

thought it looked gun emplacements.

Others believed that the site had no offensive role.

Could it have been a power station as the locals were told?

- Secret research labs, weapons factories,

rocket launchpads.

- They may have even thought that it was a decoy.

- The importance of what's going on down here

is very much in the minds of the Allies.

- Hitler's intent was to have 50 blockhauses

along this stretch of land.

The construction required

to build blockhauses is substantial.

And you wanna replicate that 50 times?

The resources, the labor, the infrastructure alone

just to build the concrete structure is massive.

- The Nazis clearly were fanatical

and clearly humanity and empathy were not a part

of any aspect of the Third Reich.

But my god, they were organized.

Some of the things they managed to do are just shocking.

- At this point with 24-hour construction,

the Germans need to floodlight the site

so they can continue working through the night.

- By this stage in the war, the Allies really

leave no stone unturned.

They are photographing every section of France

that they can get their hands on.

So they're asking themselves this question.

Why is it that the Germans are building

this obviously important site at such speed,

in full view of the Allies?

It's effectively a gigantic sign saying, here we are.

Come and bomb us.

- [Narrator] Even though the Allies have no idea

what this site contains, they classify it

as a heavy site.

Will they discover the terrible secrets hiding

inside this structure?

In 1943, Adolf Hitler ordered the construction

of a massive facility code named Kraftwerk Nord,

in the forest outside the village of Watten.

The base is 110 miles from London,

and its size makes it a target for Allied bombings.

- As fanatical as Hitler was about building the Blockhaus,

the Allies also prioritized what they

called Operation Crossbow.

This was the systematic effort to attack

every one of these facilities.

Sometimes what we don't know is more terrifying

than what we do know.

And the Allies knew that the Nazis were

working on something terrible in these facilities.

But because of the secrecy that shrouded all these projects,

they didn't know exactly was in there.

All they knew was they had to destroy them.

- [Narrator] Hitler knows this bunker is risky.

But its top-secret purpose may be the only thing

to help Germany win the war.

- They're trying to second guess what the Allies

are going to do, how they might try and defend

against your plans.

Do they know your plans?

- [Narrator] As Allied bombers fly overhead,

how could the Nazis protect this critical site from attack?

- Well, with the Blockhaus, there's no hiding it.

There's no hiding a pyramid.

There's no hiding a skyscraper.

This thing was simply so big.

So rather than try and hide the actual Blockhaus,

they just reinforced it.

- This site is so critical, that the Minister

for Armaments, Speer, orders that it's constructed

to special fortification standard, [speaks foreign language]

16-foot of concrete that can repel the heaviest bombs

the Allies can bring to bear.

- [Narrator] To make the complex bomb-resistant,

walls are built of thick steel-reinforced concrete.

- The intention with Blockhaus was that it would be

not bomb-proof, but blast-resistant.

Hence the amount of concrete used, that wall

of concrete that you're confronted with when you see it.

But building with concrete doesn't necessarily mean

you can keep bombing whilst you're building

and everything's gonna be okay.

- [Narrator] By 1943, the Allies ruled

the skies over France.

Although the German Luftwaffe still has bases

in the area, they're no match for the Royal Air Force

and the American pilots who have joined the fight.

- By now the Allies are carrying out systematic,

wave after wave of air attack against

key German positions.

So imagine if you're in the slave labor

that is constructing this enormous edifice.

You can hear the hum and the roar of the engines

as they pass over, or the single aircraft

photographing your position.

No, they weren't stupid.

They knew what was coming.

Any day now, the Allies were going to attack.

- One of Churchill's advisors, Sir Malcolm McAlpine,

comes up with an ingenious plan.

He advises Churchill to bomb the concrete

whilst it's setting, whilst it's still wet.

If concrete's hit when it's dry, when it sets,

it will crumble, it will break, it will

expose the still rebar inside.

So you've still got part of a structure there

you could patch up, put concrete back on, let that reset.

- If you drop a bomb in wet concrete,

it explodes concrete everywhere, wet concrete.

And that concrete will cure and create a crust

on whatever it touches, and it's impossible

to form and fix.

You'd have to jackhammer it out of place.

It's like putting a can of pop in your freezer

and it's exploding everywhere.

It just creates a huge mess that is really difficult

to clean up.

So the strategy of hitting this bunker

when that concrete is wet, it was a great idea.

[suspenseful music]

- [Narrator] On August 27th, 1943,

with the site just 35% complete, 187 flying fortresses

and 147 thunderbolts appear over the forest of EÉperlecques.

[speaks foreign language]

- The Allies were planning to bomb at a time

when the workers had stopped their shift

or were on a break.

They get it wrong.

The workers are there.

- The Allies, unlike the Nazis, tried to minimize

civilian casualties and especially forced laborers

from concentration camps or POWs,

some of which were former Allied soldiers.

But war being war, and a total war, and a world war

against a fanatical regime, there's simply no way

to assure that you don't have any casualties.

- This was an intense raid by the Allies.

It completely destroys the northern half of the building.

- The building's unusable, and the German engineers

must have had their hands on their heads thinking

this is just a complete disaster.

- You wouldn't wanna be the person

who had to go into the room to tell Hitler

that his cherished bunker, the place

that was gonna help him bring Britain to its knees,

had been destroyed.

- The Allies have no idea what it is they've stopped.

But they've created a massive setback

for Hitler and his plans.

- [Narrator] But the Nazis would rebuild.

And it would completely confound the Allies.

Why rebuild a structure that is in complete shambles?

Could there be a clue to the purpose of this base

hidden in the twisted remains?

What secrets did Hitler have planned

for this covert building?

[dramatic music]

August 27th, 1943, the Allies bomb a secrete Nazi base

near Watten in Northern France.

- The Allies are happy with the outcome with the air raids.

They've hit the concrete whilst it's curing

and created a mess that's pretty much irreparable.

- The idea of bombing the Blockhaus while the concrete

was wet and setting up is a great idea.

The heat from the reaction would cause the rebar

to deform and be mangled.

You would have wet concrete everywhere,

which is very difficult to fix and clean up.

The surfaces that you were on would be mangled.

And so rebuilding from that point up

would be really difficult.

It sets you back so far in the construction

that it would be so disheartening.

- [Narrator] After the bombings, Organization Todt

surveys the damage.

While the south end of the building remains intact,

the north end of the structure

has been completely destroyed.

And the shattered concrete fragments

make it impossible to rebuild.

[speaks foreign language]

- We know that as the course of the war went on

that Hitler became enraged when things

didn't go his way.

So now imagine the news gets to him

that this particular bunker complex, so crucial

to his effort, has been destroyed.

- Blockhaus was one of his great dreams

and one of his priorities.

And when it becomes nonfunctioning, one can only imagine

the violent response that Hitler had to hearing that.

- Hitler of course expects that the engineers

are gonna come up with a solution.

They're clearly looking at this site and thinking,

well we've invested so much time and so much money,

so much material, we've got to be able

to do something with it.

Otherwise we really have wasted this construction.

But because of the genius way that it was attacked

wen the concrete was setting, there was literally no way

that they can salvage this site.

- [Narrator] Determined, the Germans continued

to build the site, completely baffling the watching Allies.

- The Allies cannot understand why Hitler insists

and persists on constructing Blockhaus.

Even though it's partly destroyed, the Allies can see

how much damage they've caused from their raid.

They've created a mess.

When they hit it, Blockhaus was only 35% complete anyway.

So what is it that's going on in there

that has Hitler still trying to get it finished?

- Was this the stubbornness of the German engineers

to try and get this done despite the odds?

Was it something about their efficiency of work,

or was it fear that they felt?

- That must have been maddening for the Allies

not knowing what was happening there.

- [Narrator] But as the construction resumes,

bombs continue to fall.

Churchill won't allow the Germans

to go about their business so close

to the English Channel.

To ensure this, the British bomb the complex

four more times in a matter of weeks.

- The Allies really had no idea what the Blockhaus

was being used for.

- In the '40s, you don't have the kind of espionage tools

and tricks that you have today.

- Looking at this structure relative to the other structures

along the Atlantic wall, it's inconsistent.

It's a giant block in the middle of nowhere.

- So they're looking at this site and saying,

okay, what is it exactly?

- They may have even thought nuclear reactor.

- Maybe these sites are just more of the Nazi deceit

and decoy campaign.

Is it a waste of our resources to continue

to hit these sites?

- Lord Cherwell, Churchill's scientific advisor,

is looking at this site and he can't work it out.

He can't work out what it is.

He's looking at it thinking, well they're clearly

putting a lot of emphasis and effort into this building.

So therefore it must be worth bombing.

- [Narrator] As the Allies watch, the Germans begin

a massive undertaking and an engineering marvel.

- The design called for a concrete slab

that's 16 feet deep.

I mean, that's one foot.

So 16 times that.

In total using 37,000 tons of concrete.

The plan then is to slowly raise this concrete slab up

using hydraulic jacks, and then the walls would be

built up underneath it.

[speaks foreign language]

- Now the allies are watching the enormous roof

come rising out of the forest.

And again they're asking themselves,

jus what is going on here?

- This thing weighs tons and tons.

And it's large because the footprint

of the building is quite big.

And so they have to jack this slab up

at a consistent rate across the slab

so that it didn't have differential settlement

and potentially crack the slab as well.

The coordination required to actually

execute this plan is substantial.

- That idea to me sounds completely insane.

But they had no choice because that's the only way

that they could have constructed the building

under constant enemy fire.

[Hubert speaks foreign language]

- The engineering and resources that would go in

to taking something that weighs tons and tons and tons,

a roof, and building a facility underneath it,

it blows the mind.

The Nazis were always creative.

They were always overly ambitious.

They were not easily deterred.

And sometimes it worked, and sometimes it didn't.

- [Narrator] Set in their new plan,

the Germans construct a colossal concrete bunker,

the likes of which the Allies haven't encountered.

- And you can imagine how puzzling this must have been

for the Allies.

From what they can see, it's a giant concrete slab.

Why is there so much importance put on this?

Why go to the effort of rebuilding something

that's already been destroyed?

- The Allies continue to bomb.

The Germans continue to build.

But the only people who know what's inside that building,

are the Nazis themselves.

The Allies, they're left scratching their head thinking,

what on earth does this building contain?

- [Narrator] Throughout the autumn of 1943,

Allied bombs fall on Kraftwerk Nord,

a vast Nazi structure in Northern France.

- The Allies tried to destroy the Blockhaus

and they did hit it, but they didn't destroy it,

and it was rebuilt.

The Nazis continued producing whatever terrible things

they're producing inside.

- And somehow Blockhaus managed to maintain its secrecy.

Why go to to the effort of reconstructing something

that they've already destroyed?

- [Narrator] After the bombings, Adolf Hitler

meets with Albert Speer, and Organization Todt

chief engineer Franz Xaver Dorsch,

to discuss the Kraftwerk Nord problem.

With the structure now damaged, they decide

to build another site only a few miles away

at a quarry they had been using for storage.

Why would the Germans not only rebuild Blockhaus,

but also build another site so close nearby?

- Hitler decides to construct another site,

but this time taking much of the operation underground

to give it an added layer of protection.

Add to that the roof this time would be in a dome shape

to give it more structural integrity,

and to provide more protection from the bombs

raining down from above.

The fact that Hitler decides to keep building,

despite the failures, despite of being warned

in the past that big bunkers were not the way forward,

just goes to show how important this Blockhaus was for him.

At any cost, it needed to work.

- [Narrator] The Nazis spent another year building the site,

having it blown up and rebuilding it.

What new purpose could they have

for the wrecked Kraftwerk base?

- By now the Germans even understand themselves

that the Blockhaus is just too juicy a target

not to hit.

So they keep on building giving the Allies the idea

that it was still worth bombing.

Meanwhile, they're building elsewhere.

This could be yet another sign of the German ability

to use information to misdirect their enemy,

to confuse their enemy, and to make the best

out of a pretty bad situation.

- You know it was this cool game of the dog

chasing its tail in a circle.

The Allies bomb the facility.

The Nazis rebuild it.

The Allies bomb it.

The Nazis rebuild it.

Now it's a drain on both sides.

The loss of bomber crews was shocking

as Nazi antiaircraft were shooting these down.

The more the Nazis are forced to rebuild,

they're running out of money.

They're running out of concrete.

They're running out of everything at the end of the war.

But it begs the question, if something is worth rebuilding

time and time and time again, there must be something

awfully important going on inside that facility.

- [Narrator] On June 19th, 1944, an Allied raid

drops a powerful new weapon on Kraftwerk Nord,

the Tallboy bomb.

- Warfare is always a matter of keeping with the Jones's.

The enemy makes a powerful weapon,

so you need a more powerful one.

- The Tallboy was an earthquake bomb

designed by the British towards the end of the war.

And it was so heavy it could only be carried

by a Lancaster bomber.

- So these earthquake bombs were capable

of just massive destruction.

And they had a fuse and a design that they could bore down

and then detonate rather than detonating on impact,

which would have more of a chance of destroying

something like the Blockhaus.

- It goes into the core of the structure

sending shockwaves throughout all the structural points

in the building, effectively rendering it useless.

- It's almost like the Tallboy is quite literally

ripping the guts out of a building.

- To guarantee the success of the Tallboy bombs,

each one had three delay fuses.

So even if two didn't work, the third one hopefully would.

- [Narrator] The shockwave caused by the Tallboy

devastates the site.

- When the bomb hits, some of the German soldiers

are killed by the actual explosion itself,

but just from the sheer shockwave was sent out,

its destruction ripples through the entire structure.

- With one bomb, you can create a much bigger

site of destruction.

- It will find weak points.

It will topple over anything that is not robust enough

to withstand that energy and will potentially cause

internal collapse of any load-bearing elements.

It's like if you were to put a firecracker on your hand,

light it and let it go, your hand's going to get burned

because the firecracker's gonna disperse

and it has environment to work its energy out into.

However if you were to close your fist

and light that firecracker, your gonna lose your hand

because that energy is confined and its going

to rip through your hand.

- Whatever's left over would need to be discarded

because there was really no way of reconnecting

the steel that would have been destroyed or bent,

leaving Hitler with the only option

of completely restructuring the building.

- The Tallboys were incredibly destructive.

There's craters that were 80 feet in diameter

and up to 100 feet deep.

And that is the result of the Tallboy.

You can imagine containing all that energy

inside of a bunker.

It would blow it, blow it to smithereens.

- [Narrator] In July of 1944, the Allies dropped

15 more Tallboys on the Kraftwerk Nord site

and 16 on the Wizernes bunker.

Even after being hit with so many

of the Allies' powerful new weapons,

the Kraftwerk Nord site still stands,

and the Germans don't give up on it.

- The Germans keep building it.

So there must have been question marks

popping up all around the place.

Why is it that they're so stubborn,

and they're prepared to build again and again.

Each time we attack, they keep on building.

The secrets of the building must have been

driving the Allies crazy.

- [Narrator] In a forest in Northern France,

Allied Tallboy bombs devastate a mysterious

concrete structure built by the Nazis

for a secrete purpose.

Though the base has lost its original capability,

the Germans have new plans for it.

- The Germans do notice that the Allies are paying

a lot of attention to this site because they don't know

what's in it.

So they decide to use the site

for another purpose, deception.

- And they continue to build it just to draw in

Allied ammunition, Allied effort, Allied energy

that might have been deployed elsewhere.

- They developed a lot of decoys.

They used deceit and misinformation as a front

in the war, and they were very good at it.

- Perhaps it was not just a decoy,

but it was also them understanding

how they can construct buildings that would be able

to withstand some sort of substantive impact.

- The Germans came up for a code name for Blockhaus

in the end.

Translated it means concrete lump.

- [Narrator] On September 4th, three months

after the D-Day invasion, Canadian forces

captured the site.

Would the remains of this facility provide any clues

to its intended purpose?

- One can only imagine what the Canadian liberators

felt when they walked upon such a structure

in the woods.

And the first scientists who were brought in

to figure out what was going on here,

must have just scratched their heads and been in awe.

- All of the documentation that may have been in there,

would have been destroyed.

And it's a testament to their abilities

of secrecy and misdirection that the Allies

were not able to determine what the building

was to be used for.

- Even after inspection by some of the top Allied experts,

they're still not able to work out

what the purpose of this site was.

The mystery of the building continues.

[speaks foreign language]

- [Narrator] What the Allies discover is

shocking and terrifying.

This structure was designed to launch

the new V2 rocket, capable of raining down

unheard of destruction on cities as far as London.

- By 1943, the complexion of the war has changed.

The Luftwaffe does not control the skies.

The Kreigsmarine does not control the seas.

Hitler is not able to expand the Third Reich.

He needs a hail Mary at the end of the game,

something so terrible that it'll change

the complexion of the war.

- If I'm an engineer and I'm working for the Third Reich,

I wanna find something that is innovative.

We want to get a leg up, and we need something

to help us.

And part of that plan was the V2.

- [Narrator] At Peenemunde Army Research Center,

top rocket scientists and minds in Germany

were hard at work designing this cutting edge new weapon.

- Wernher von Braun, the famed rocket scientist,

was the lead scientist there.

This is where they were developing Hitler's

mad wonder weapons.

Rocket technology was in its infancy

and thus comes the V1 and then the V2.

- Hitler sees the V2 as his vengeance weapon.

He can't continue to fight this war simply

on land and in the air.

He needs a new weapon, and the V2 is it.

- This is the largest, fastest, most powerful rocket

of its time.

It's capable of traveling all the way across

the Channel with ease.

And they produce a few thousand of them.

- It's tempting to dismiss these wonder weapons

as then glorious fantasies of Hitler's crazed

and deranged mind.

But you only have to look at Hiroshima and Nagasaki

to understand the wonder weapons of a nuclear scale

changed the tide of the war.

They quite literally brought countries to surrender.

- [Narrator] Because Germany had some of the best minds

in physics and rocketry, the V2 program

was a true breakthrough in technology.

- The Germans were, a lot of the time

way ahead of the game.

And the same can be said for their know-how

on rocketry and ballistics.

- Everything the Germans seem to have done

has a feeling of efficiency and precision and progress,

just an interest in stepping forward.

- The scientists were thinking out of the box.

What's next?

What new fantastical and terrible weapon

are they gonna produce?

- [Narrator] Unlike the V1 rocket, which has been

previously used throughout the war,

the V2 shoots straight up into the thermosphere

before plummeting back towards earth

to hit its target.

The missile has a range of 186 miles

and is virtually invulnerable to radar and antiaircraft.

- The V2 rocket was just a massive weapon.

It was 45 feet long.

It weighed 27,000 pounds.

It could travel 80 kilometers into the air,

and it traveled at speeds that were

up to 3,500 miles per hour.

- In order to achieve that, the rocket's tanks

hold 9,200 pounds of ethyl alcohol,

and over 12,000 pounds of liquid oxygen.

That massive amount of fuel contained within the rocket

is then pumped through 1,200 individual nozzles

at exactly the right ratio to achieve the perfect mix.

- The V2 rocket also contained a pretty

sophisticated guidance system.

There were two gyroscopes which indicated the position

of the rocket, and it also had an accelerometer.

That was a critical component of the guidance system

because it told when the rocket needed

to basically shut off so that it would

reach its intended target with its ballistic trajectory.

- The V2 weapon is so advanced it's virtually impossible

to detect, to track and to counter.

- Even if you could track it, there was no

antiaircraft system, no plane in the Allied arsenal

capable of flying remotely that fast

to try to shoot this thing down.

It was basically a bomb with a tail on it.

[speaks foreign language]

- The V2 rocket is so advanced, it becomes

the first manmade object to travel into outer space.

On the 20th of June, 1944, one V2

crosses the common line, which is basically

the boundary between the earth's atmosphere

and outer space.

And you can see why further on down the road

the Americans become very interested

in German rocket science.

- [Narrator] In early 1942, Hitler set a goal

to fire 144 V2 missiles per day.

- The damage from one V2 hit, could complete take out

a multi-story building and kill hundreds of people.

So imagine what Hitler's plan was, to rain down

hundreds of these rockets every single day

on metropolis like London and other big cities

on British mainland.

- The warhead of the V2 rocket is 2,100 pounds.

But 2,000 pounds of that is explosive.

That ratio is astronomical.

It is 93% explosive power.

- I would imagine that it could basically wipe out

the entire city of London within that one day.

[speaks foreign language]

- The V1 rocket had a signature.

They could identify the rocket.

It had a very distinct sound.

The V2 didn't.

The V2 hit before you knew it was coming.

It enhances the psychological terror aspect

of the weapon.

- Some people said they saw nothing.

Some people said they saw a thing streaking

in the sky.

All the people said that the explosion

was like nothing they ever heard before.

And it would obliterate entire blocks.

Hundreds of people murdered.

And they don't know where it's coming from.

- [Narrator] The plan called for 50 V2 sites installed

across the Western front.

- All of that is within 300 kilometers of London.

So London and other large cities on British mainland

are well in range here.

And that is an insane amount of firepower

that would have rained down daily

onto the British mainland.

Hitler's convinced that this plan and this firepower

is gonna bring Britain to its knees.

- [Narrator] The V2 appeared to be the game changer

Hitler was after.

But with the Nazis losing ground in the war,

how would they produce and launch enough V2s

to turn the tide back in their favor?

- Well, Hitler was mad.

And Hitler's folly, his continually making

the wrong decision helped the Allies win the war.

He set goals to launch so many rockets per day,

the goals were utterly and fantastically unrealistic.

So these things use so much liquid oxygen,

and this is enormously expensive,

time consuming to produce, and by 1943,

Nazi Germany's running out of money.

They're running out of resources,

and most importantly, they're running out of time.

- Despite engineering challenges along the way,

the V2 is eminent.

The challenge now is to be able to launch

these V2 rockets in volume and with maximum efficiency.

Hitler's vision for the V2 rocket launch site

is through a series of well-entrenched,

well-defended bunkers.

They're static but we're talking about high volume.

- [Narrator] Albert Speer, Hitler's chief architect,

recommends mobile launchers called meillerwagen,

portable trailers with hydraulic lifts

and built-in fuel tanks.

- Albert Speer and Hitler got into a disagreement.

Speer says we should not build more hardened sites

to launch these.

We should put 'em on a mobile rail,

a trailer perhaps.

That way we can launch and hide.

- All of this is happening within the context

of a huge amount of air force activity.

The Allies are sending out planes on a daily basis.

They're bombing.

Albert Speer's argument is that by having static bases,

they're vulnerable to attack, constantly.

- Fortunately for history, Hitler overruled him

and said no, we build hardened sites.

Had Speer carried the day in that argument,

the number of casualties inflicted

would have been exponentially higher.

- [Narrator] From this site, Hitler intended

to launch a quarter of his planned V2 missile capacity,

36 missiles per day, straight towards London.

But those plans would never be carried out.

The devastating allied bombings in August, 1943

destroyed the north end of the building,

crippling the site's launch abilities.

However, the south end remained intact,

and the Nazis had a new purpose for it.

In a Northern French forest, an allied Tallboy bomb

destroys a V2 facility built by the Nazis

to launch a space-age weapon that could have changed

the course of the war.

- The V2 launch site at Blockhaus was

a failure ultimately.

No V2 rocket was ever launched there.

Even after it's captured and inspection by specialists,

the Allies still can't work out what secrets

were held within Blockhaus.

- [Narrator] Hitler orders the Blockhaus built

110 miles from London, well within V2 range.

- Hitler wants dozens of V1, dozens of V2 sites.

He's limited in where he can put them

because of the reach in terms of the rocket.

So he needs to place them strategically.

- [Narrator] It's built to be a one-stop shop

for V2 production, a railway station,

V2 assembly factory, liquid oxygen plant

and launchpad all in one.

- When they first built the Blockhaus, it was going to be

where they assembled parts of the V2.

They don't construct them completely.

They were still on rail bringing the parts

into the Blockhaus.

They assemble them there, and they can launch it there

and from France, they can still hit the targets

that they need.

- [Narrator] Liquid oxygen would be produced onsite

to minimize volume loss.

- Creating liquid oxygen is no easy process.

Oxygen, as we have around us, wants to be a gas.

If you're making it into a liquid,

it requires a huge amount of energy and effort

to keep it as a liquid.

Once you've got liquid oxygen contained in tanks,

it wants to get out and it will dissipate over time.

So you want the shortest distance possible

from its construction and storage

to where it's gonna be used.

- [Narrator] The V2s would be hooked up to fuel sources,

loaded with explosives and moved outside

via rotating doors to be launched rapidly.

The devastating Allied bombings in August, 1943

destroyed the north end of the building.

- By now Hitler and Speer have had to give up

on the Blockhaus as a launch site for the V2 rocket

that's gonna change the war.

And they do have other plans.

- [Narrator] The south end of the building

containing the liquid oxygen facility

remains intact.

- The V2 production is still going on,

and they still need the phenomenal amounts

of liquid oxygen for other rocket sites.

They're already building a better launching facility

not too far away, using the liquid oxygen

that they're now producing at the Blockhaus site.

- [Narrator] Following the Tallboy bombings

in the summer of 1944, Hitler moved the V2 facilities

back to Germany away from the Allies' reach.

Yet even after capture in September of '44,

this would not be the end of the building's story.

- The Americans developed the Dizzy bomb,

which is a 4,500-pound bomb.

And they needed somewhere to test it.

What better place to test it than on a bunker

that was built to withstand bombs.

- It's built proper solid.

It's far enough away from civilization

and it's massive.

What was once something they wanted to bomb,

funnily enough they still want to bomb,

but for very different reasons.

- We would normally test something like this

on the computer, using computer simulations.

Rarely would there even be access to a structure

that would have been fortified as much

as the Blockhaus had been, that they could use

to carry out physical testing.

- [Narrator] Hitler's V2 dreams never materialized

and the war ended soon after the events at Kraftwerk.

Yet the secrets of the V2 program

would not be lost to history.

- The Third Reich is over.

The vision Hitler had completely destroyed.

But the fruits of the scientific endeavors

that the Reich was dedicated to, remain.

- When the war ends, the United States does a

snatch and grab effort with something

on the order of 1,500 of Nazi Germany's leading engineers,

leading scientists, among them Wernher von Braun.

And rather than have them face trial at Nuremberg,

or rather than put a bullet in their head,

we bring them back to the United States.

The V2 was one of the most diabolical

and deadly weapons of its time, used for purposes of evil.

Yet the V2 gave birth to the kind of rocket technology

that allowed us to go to the moon and explore space.

- [Narrator] Some 5,000 V2s were produced,

and over 3,000 launched against Allied targets.

An estimated 9,000 casualties were inflicted

by this new technological terror.

- Luckily for the Allies, and indeed

for the rest of the world, the V2 program

came into place too late in the war to have a real impact.

We can only imagine what would have happened

and the number of people whose lives would have been lost

if Hitler had decided to build this program earlier on,

and what would have happened if he had followed the advice

of his advisors and generals and picked the mobile

rocket launchers rather than the fixed sites

in the Blockhaus.

- When I see the Blockhaus, I would expect there

to be quite a bit more destruction visible.

It makes me fairly impressed that they were able

to still maintain this type of structure

despite the intense bombing.

- I'm always impressed by the scale

of what mankind can build.

When you see Blockhaus and something else happens to you,

it's quite intimidating.

- The Blockhaus is a monument to engineering

and science at the time.

And it's a very eerie reminder of the destruction

that can also impart.

- The Blockhaus is Hitler's sought-after dream

of an impregnable fortress.

It's bombed, and bombed with some

pretty impressive weapons, and it doesn't destroy it.

It seems to be indestructible.

- [Narrator] We can only speculate what kind of destruction

Kraftwerk Nord might have unleashed

had the Allies not destroyed it.

The V2 might have been the weapon

to bring about German victory, launched from right here

in the woods at this secret Nazi base.

[dramatic music]