All language subtitles for Secret.Nazi.Bases.S02E02.Lurking.in.the.Shadows.1080p.AMZN.WEB-DL.DDP5.1.H.264-BurCyg_track3_[eng]

- [Narrator] In total secret,

Germany rapidly builds a
series of complex hydro works

in its eastern territories.

- This is an immense
infrastructure project.

It really is on a grand scale.

- [Narrator] Damns, canals,

and swinging
bridges are erected.

- Germany created it
only in two years' time.

- [Narrator] But this
is only the beginning.

Construction morphs
into massive tunnels,

bunkers, and concrete
teeth built into the earth.

- You look at it, it just
looks [pausing] evil.

- [Narrator] But what's
beneath these structures

is something else entirely.

- It's an underground
city down there.

- [Narrator] Allies are unaware

of Germany's true intentions.

- It would take a lot of effort
to hide all of that material

that's coming on to
site for how many years?

- [Narrator] What
could the purpose be

for such an elaborate
construction project?

- You have to understand,
this is a project

costing hundreds of
millions of Reichsmarks.

This is one of the
biggest things they'll do

in 1930s Germany.

- [Narrator] The Nazis
have frightening plans

for this region and intend
to protect it at all costs.

[suspenseful orchestral music]

[door slamming]

1932.

Post-World War I.

Germany is forbidden
from rearming,

but a lot has changed
since the '20s.

The Nazis are coming to power
and they have ambitious plans.

But unbeknownst to
the Allied powers,

construction on a vast project
begins in total secrecy.

Under the guise of a
highway being improved,

massive construction

in the eastern region
of Germany begins.

Forests are cleared,

canals carved into the terrain,

and secret tunnel
construction begins,

as an ominous project
slowly takes shape.

- The Nazis were
obsessed with secrecy,

and in all respects they
went to great lengths

to try to deny realities
of what was going on.

- The simple truth
is if you talk,

you're imprisoned
[pausing] or worse.

- Amazingly, they were
able to do a lotta this

straight under the noses of
the world and get away with it.

- [Narrator] Germany sets to
altering the landscape forever

with an expensive hydro system.

- If you are today in
the area of Festung,

you see beautiful nature,
full of rivers, forests.

But if you realize that
there is only one river

and hundreds of the
fortified canals,

very artificial, built
by Germans in the '30s,

you realize how this
huge system was extent,

and Germany created it
only in two years' time.

- [Narrator] One of these
secret construction projects

is a massive bridge.

- Water's a big force.

It can change the landscape.

It can be unpredictable
depending on its source.

And building in water
is really hard as well.

Think of building a bridge.

You have to span over
this length of river

and build abutments and
then build the structure

to bridge those abutments.

It's not an easy task.

- [Narrator] But the
complexity of this build

doesn't end here.

The bridge is imbued
with a special ability:

It can be swung out

and then brought back
to a neutral position.

- When you think about
wanting to move a bridge,

you're now merging two systems.

You have this structural system
which is static, a bridge,

but then you're turning
it into a machine

by introducing gears and
motors and pinions and racks

and counterbalance
and ropes and pulleys.

It's changing the
nature of this structure

to be much more complex.

- [Narrator] Even in the '30s,

this bridge was outfitted
with an electrical system

that allowed for the easy
movement of its platform.

- Moving a bridge of this size
is a complex feat on its own,

especially considering
the electric systems

that were available
in the 1930s.

But it's also been
designed and built

with a backup ability to be
opened manually if needs be

with the force of just
one or two people.

And it's amazing to
me that it still works

to this day, some
80 years later,

because the Germans
were at the forefront

of technology and engineering.

- [Narrator] But the
design of this bridge

seems to raise only
more questions as
to its true purpose.

When engaged, the platform
swings out into the canal,

seemingly cutting
off water traffic.

- Movable bridges today

allow for two types of
traffic to use them.

We have vehicle traffic on top

that goes over the bridge
when the bridge is in place,

and then we move that
bridge outta the way

via a swinging motion or a
tilting motion or a lift motion

to allow for marine traffic

to go under and
through the waterway.

But this bridge had a
completely different intent.

- But when this bridge opens,

it's right in the middle
of the river still.

It's still blocking
the waterway,

which doesn't seem like any
kind of design of bridge

that you'd need for building
a road or a highway.

So, what is going on here?

- [Narrator] Perhaps a clue
for Germany's motivation

could be gleaned from
the location itself.

While this territory
is now part of Poland,

it was previously
occupied by Germany.

- This is territory which
is really vulnerable.

It's quite open,
relatively flat.

It's a fairly accessible
corridor for a foreign army.

- [Narrator] And this
area is very close

to the heart of the
Third Reich: Berlin.

In fact, one can travel by
vehicle from this region

to the German capital in
less than three hours.

- So, it hits all
of the high marks

for German obsession with
it, right, to protect it.

- [Narrator] Could this
structure's proximity to Berlin

explain its design?

- The fact that when
this bridge opens,

not only does it still
block the waterway,

it also creates a
gap in the roadway,

and it makes you think, "Maybe
that's exactly the point.

"Maybe this is a
defensive structure

"to prevent people accessing

"what's on the other
side of the bridge."

- [Narrator] Suddenly,
a clearer picture

of Germany's intention for
this bridge begins to form.

- It was used to
control who and when

was able to traverse
that waterway.

- [Narrator] But
the swinging bridge

is only a piece of a
much larger puzzle.

Dams and canals are put into
place throughout the region

with the ability to
quickly flood areas.

- It is a little medieval,
using water to instill chaos

or control the access
to this parcel of land.

We don't really use
water in that way today.

We use water in other ways.

We harness it for energy
turbines to generate energy.

We use water for
good. [laughing]

This was a much more sinister
use of an energy source.

- To build a concrete wall
to prevent trucks and tanks

from approaching your
position is very expensive.

We have to move a lot of
material to construct a wall.

It's not simple, it's not easy.

Whereas if I build
a couple of dikes,

I build a couple of dams and
have some controls to pump

or to allow water
to flow naturally,

I can achieve essentially
exactly the same thing

with far less manpower,

with far less movement
of material and goods.

- Any time an army
has to cross a river,

it becomes more tricky.

So, if you up the
ante by building

some complicated fortifications,

you make it easier to defend.

- If we imagine
those invading forces

trying to seize the area
and trying to reach Berlin,

for sure, they would be stopped
by this hydrology system,

which makes the area around
impossible to break through.

- [Narrator] While
a few waterworks

to allow for a highway
might be one thing,

this is on a scale so immense

it has the rumblings
of a fortification

rather than roadwork.

- This is an immense
infrastructure project.

I mean, it really
is on a grand scale.

But it was done in a way
that wasn't grossly obvious

because you were building
small pieces at a time

that built up to a
much larger thing,

rather than having tens
of thousands of people

building one large obvious
structure all at once.

- [Narrator] What could
the Nazis' intentions be

for this region and
the massive hydro works

that they've created?

- Hitler's looking around and
seeing threats everywhere.

The French have already started
building the Maginot Line,

the world's most technically
advanced static line of defense

from the late-'20s onwards.

So, he sees this
threat from the west,

and Hitler's answer to that
is his own Maginot Line,

the Festungsfront on
the eastern border.

- [Narrator] Beyond the
hydrological defenses,

an even more massive
construction project

begins in the region.

Steel and concrete is quickly
smuggled into the area.

- Could this have
been interpreted as a
highway at the time?

This was very obviously
military-related.

You look at it, it just
looks [pausing] evil.

- I can't imagine how
you can keep a secret.

The continuous
delivery of trucks

full of aggregate,
full of concrete,

full of just all
of the materials

that you need for
your construction.

- [Narrator] Polish
spies and intelligence

manage to infiltrate the area

and suspect that
this is something

far greater than
highway construction.

- Polish intelligence
have absolute knowledge

that from the other side
of the Polish border,

something about 30
kilometers from Poland,

Germans are building
huge fortification line.

- [Robert] You get a
sense of real dread

because you've faced
the German army before.

You know that these
are fortifications

the likes of which you've
not really seen before

at any point in the war.

And this is not a state
that's giving up easily.

- The road to
Berlin is wide open.

Festungsfront is the
gate that slams it shut.

- [Narrator] But this is
just the tip of the iceberg.

Unbeknownst to Soviet
and Polish intelligence,

Germany is building
something underground

that is more secret and colossal

than they had ever imagined.

Across a vast area
in eastern Germany,

a massive construction
project is secretly underway.

Germany believes whatever
invading force comes

will be vastly different

from what it had previously
seen in World War I.

But this is just the
tip of the iceberg.

Germany sets to building
hundreds of concrete structures

across the Festung region.

Jutting from the earth,
over three feet tall,

are some cement dragon's teeth.

- They stretch as far
as the eye can see.

- It's obviously purposeful
and out of place,

and it gives me a
sinister feeling.

- [Narrator] These aren't
merely concrete structures.

They're reinforced with steel

to ensure their destruction
would be nearly impossible.

- In general, as engineers,

when we see a reinforced
concrete structure,
we start going,

"Oh my god, how am I
actually going to move this?"

- What on you see on the surface

are these dragon teeth
jutting out of the ground.

But what you don't
necessarily see

is that there are huge great
slabs of concrete underground

that connect all
these teeth together.

They combine them as
one great long carpet

of dragon's teeth,
if you'd like.

- [Narrator] What
could the purpose

of these jagged structures be?

- World War I has
shown that the next war

will probably be mobile.

Tanks almost played
a crucial role,

and the Germans were
caught on the back foot.

Hitler's determined not to
make that mistake this time.

- They recognized that tanks
were going to get bigger

and better and
faster and stronger.

You need to build a blockade
to prevent an attack

of this mechanized
new military machine

that you need some
incredible embattlement,

some system to
prevent those tanks

from reaching your facilities.

- There's no way any
motorized vehicle

was gonna make its way
successfully across this.

- [Narrator] Why would Germany
favor such a strange design?

- Another option
to stop vehicles

might be a really large wall.

You could build a vertical wall.

That would also need
a really large footing

underneath the ground to prevent
that wall from overturning.

Whereas with the dragon teeth,

we have individual
superstructure,

structure that's
above the ground,

tied together with a more
efficient underground footing,

so you'd likely use
a lot less material.

You don't have to build
all the vertical rebar,

you don't have to form
up the vertical wall,

and you have probably
a smaller footing

to deal with that overturning.

- The construction of the
dragon's teeth at Festung

is so strong that after the war,

Polish army would like to use it

and they were
trying to remove it.

But they used so many
resources to do it,

but totally unsuccessful.

That's the proof
how strong it is

and how complicated
the construction is.

- [Narrator] While
the dragon's teeth

are powerful enough as they are,

they still possess yet
another devastating function.

- As if the front itself
wasn't heavily defended enough,

the Germans even think
up this mini canal system

connected to the dragon's teeth

which could be flooded
at a moment's notice.

- [Narrator] The dragon's
teeth wouldn't stand alone

to fend off an attacking force,

but act in tandem with other
elaborate defensive measures.

- The dragon's teeth
are the foundation,

kinda this concrete
permanent structure

of this defense line, but
there would also be trenches,

there would be barbed wire,

there'd be other
mechanisms in there

to deter people from
going in, soldiers,

and other smaller
vehicles passing through.

It was part of a system
that was built up

and layered upon to build
an entire defense line.

- It's absolutely massive.

It's designed as effectively
a dividing military line

between themselves and
the eastern territories.

- [Narrator] Beyond this
complex series of waterways,

trenches, minefields,
and anti-tank barriers

lie some of the
most sophisticated

defensive structures ever built.

Hitler had been a
corporal in World War I

and saw firsthand the downfall
of primitive trench warfare.

- Germany really learned
a lot from World War I.

A huge amount of the military
casualties in World War I

were as a result of the
conditions in the trenches.

- And the biggest
problems were, one, rain,

'cause the men were
out in the open

and any trench or
bunker would flood;

two, rats, the infestation
from rats; and three, disease.

If it was a rainy season,

you were ankle or
knee-deep in muck,

and diseases were spread.

- [Narrator] In 1929, France
has started to develop

the next generation of static
warfare: the Maginot Line.

Comprised of
interconnected bunkers,

it was to be the next
generation of static warfare.

- So, the Nazis are in an
arms race with the French.

The French have
the Maginot Line,

and now the Nazis
have Festungsfront.

- What these fortifications
do is to try to close up

that really vulnerable
corridor into Berlin.

That's a knife that is thrust
at the heart of Germany

in no uncertain fashion.

- [Narrator] Germany's
answer to what's been seen

on the Maginot Line
is the Panzerwerk,

a heavily-defended bunker.

- Those bunkers are
like nothing we've seen

anywhere else before.

- [Narrator] Germany develops

its own advanced bunker
system, the Panzerwerk.

- This system would
enable the Germans

to maintain almost
indefinitely a defense.

It was really ideal
for making sure

nobody could ever
get past this point

and was an innovative idea
to address all the issues

that occurred in the
trenches in World War I.

It really was an
amazing undertaking

to protect themselves
from future attacks.

It's gonna change
the battle entirely.

- [Narrator] The
bunkers were built

with massive concrete walls

that were between
three and 10 feet wide.

- If you spot someone pouring

nine- or 10-feet-thick
concrete walls,

that's something to
pay attention to.

- Whatever is down there,

if you're pouring
that much concrete,

you want it to be protected.

- Reinforced concrete is a great
way to construct a building

that starts to become
virtually indestructible.

Short of launching massive
ton-sized munitions,

these structures were gonna
be essentially impenetrable.

- The bunkers are also
built into the hill.

They're using this natural
landscape to help build form,

to create these bunkers,
to hide them as well,

and to allow these
structures to be buried

to protect them from any impacts

from bombs or other artillery.

- [Narrator] What could
the Nazis be hiding

beneath these bunkers

that made them go to such
great lengths to defend them?

Germany sees France's
Maginot Line to the west

and sets to creating its
own massive defensive line

called the Festungsfront to
protect the road to Berlin

from any
eastern-invading forces.

- What on Earth is going on
down inside these bunkers

that would make the
Nazis put so much effort,

so much expense into
fortifying them?

- [Narrator] Fixed
atop each bunker

were steel domes
known as cupolas.

These armored domes
were constructed

with thick steel walls
at least three feet wide.

- Some of these cupolas weighed

the equivalent of two
T-34 Russian tanks.

That is incredibly heavy!

- Those cupolas was extremely
strong and powerful,

but also extremely expensive.

- It's not necessarily
overkill, though,

if you are designing it
for a specific purpose.

You must be putting them there

so that it protects
you from bombs.

- You can see one of the
cupolas has gouges out of it.

It looks like clay almost,

and those are
remnants of shelling.

And what happens is the
shell with this huge energy

hits this steel and
the steel deforms

and dissipates
that energy through
deformation of the steel.

- [Narrator] These
weren't simply domes.

Utilizing unique mechanics,
each cupola could be rotated,

becoming a deadly turret.

- There had to be some
sort of track at the bottom

and some sort of wheels to, one,

bear the weight
of those cupolas,

as well as allow someone to
manually rotate these cupolas

via a gearing
system to translate

that energy, that human energy,

into moving this massive
chunk of steel around.

It's likely a pretty
efficient system.

- [Narrator] Concealed
inside of the cupola

were state-of-the-art
machine guns

capable of
frightening firepower.

- To top it all off, the
Nazis bring the MG 34 to bear.

This was considered
the most advanced

general purpose machine
gun of its time.

In '36, they're already ready

and they're arming that
line to the teeth with them.

I've seen them myself,

and the idea of trying to charge
up against this machine gun

capable of firing
900 rounds a minute,

it brings chills to my body.

- [Narrator] World War I
brought a frightening new weapon

to the battleground:
mustard gas.

- The prolific use of
mustard gas in World War I

prompted the Nazis
to build this complex

so that it was protected
against any gas attacks.

- You had to think about, "How
do we deliver enough oxygen

"for the occupants," and
manage also these explosions

that were happening that could
suck that air pressure out,

that could change the
toxicity of the air,

that could cause people
to die, to suffocate.

- But it also had
state-of-the-art

air filtration and
ventilation systems,

meaning that if they needed to,

they could stay underground
for months at a time.

- [Narrator] Tucked away
in one of the rooms,

experts find the remnants
of a mysterious machine.

- When you look
at this machinery

and the room that it's
all contained within,

it's quite eerie, to be honest.

You get a feeling deep down
that this is all geared

toward something quite brutal,
something quite sinister.

- [Narrator] Pipes lead
from this ominous machine

to the surface
level of the bunker

and then stretch all the way
down to massive reservoirs.

- When you look at the mechanics

and the infrastructure
within this room,

it seems to be that
it's all about moving

large amounts of fuel
and moving it very fast,

which to me says one
thing: flamethrower.

- Positioned at the top of
each of these bunker complexes

is a two-and-a-half-ton
FN flamethrower

capable of firing
out sheets of flame

that would've incinerated
anyone for up to 60 meters.

- Fire is a very
effective deterrent.

A soldier's far more
willing to charge

against a position with a gun

than they are with
a flamethrower.

It's visually obvious to
the attacking soldiers.

It's a psychological barrier
for the attacking force

to try and take that position.

- The rush of flames,
the visual, it's
just fear-inspiring.

It would be crushing.

- [Narrator] Each FN
flamethrower came equipped

with a staggering
reservoir of fuel,

which housed an impressive
2,500 liters of fuel.

- For comparison, today's SUVs,

an average SUV has 50 to
60 liters of fuel in it.

This flamethrower had access
to 2,500 liters of fuel.

That's 50 times a single SUV,

and it would burn 27 liters
of those in one minute.

That would burn half a tank of
your SUV fuel in one minute.

It's unreal.

- I just can't
imagine the intensity

or the size of flame that
that's gonna produce.

Absolutely terrifying!

- [Narrator] Still deeper
in this bunker complex

awaits another secret.

- As if all of these
defenses weren't enough,

the Germans have the MG
19, a grenade launcher

capable of firing
120 rounds a minute.

If you're an
advancing infantryman,

not only would the
ditches slow you down,

not only would the
barbwire stop you,

but these grenades will cut
you to pieces in seconds.

- [Narrator] The MG
19 grenade launcher

contains one of the
earliest targeting systems,

accounting for trajectory,
wind speed, and velocity.

This weapon could
deliver a shell

on advancing forces
with deadly accuracy.

- In the 1930s, the
Germans started developing

systems that would
automatically calculate

all of those parameters for you

so that you could more
accurately guide the shell

or direct the shell to
where it needed to land.

- [Narrator] Still, there was
yet another devastating weapon

housed in these
concrete bunkers:

the MG 08 heavy machine gun
stationed at the bunker door.

This weapon was capable of
delivering a deadly barrage

that could devastate
enemy troops

with a range of over 6,000 feet.

The design of the
bunker was so complex

it even had special
modifications

which protected the
operator of the MG 08.

- In the bunker wall,
they would've had openings

for machine guns, and
the openings are stepped.

So, at the interior, the
opening is quite small,

and it steps out as you get
to the exterior of the wall,

and this would
allow a machine gun

to protrude out into the opening

and allow it to maneuver
from left to right.

And it also protected the user
by stepping in that opening

to keep that opening
as small as possible,

but allow the range
of motion of the gun

to be as wide as possible
at the same time.

- [Narrator] But
the deadly design

of this bunker doesn't end here.

If invading forces manage
to make it into the bunker,

a surprise awaits them.

A strange metal
sheet would swing up,

revealing a pit below.

- It's a trap door.

It's like something out
of a medieval castle.

I guess it proves that
sometimes the old methods

are the most effective.

- Even if you get
to these positions

and you start taking
these positions,

you're certainly still
not gonna be able

to get into the larger complex

and attack the soldiers therein.

- The Nazis, they wanted
to build themselves

and protect themselves

further and deeper
into their bunkers,

and how can they do that?

How can they stop people
from entering further?

So, various characteristics
like narrow hallways

and inset machine
guns here and there,

and traps, essentially, to
prevent any sort of assault

from getting deeper
into the bunker.

And they would have
stores and safe spaces

further in their bunker for
them to survive, basically.

They wanted to
lock themselves in.

- The Festung is
the most advanced

and modern fortification system
maybe even in 20th century.

- When you actually look
at these structures,

they're terrifying.

They have enough armament

and capabilities to
defend themselves.

They have enough
people and supplies

almost to defend
themselves in perpetuity.

"Even if the attackers come,

"I'm comfortable sitting
in here, defending myself.

"Let them wear themself out

"and fall at the feet
of my door in futility."

That's kind of what
these structures were.

- You put this together,
the heavy artillery,

the dragon's teeth, the canals,

the ditches, the barbed wire,

the machine guns,
the grenade launches,

and then, to top it all off,

this complex series
of flamethrowers;

I mean, if any infantrymen
had been able to get close,

they would've been
absolutely terrified

and it would've
been sheer murder.

- [Narrator] This is just
the tip of the iceberg.

Beneath these bunkers
lie even more secrets.

Breaking the terms of their
defeat in World War I,

the Nazis are building a
top-secret massive complex

of defensive systems to
guard the gateway to Berlin.

- This is the advent
of the Autobahn,

the advent of
these mega-projects

that are really on a scale

that is well beyond what
man had done previously,

that would be something
that any attackers

would not be
anticipating in that era.

I mean, this is totally
new to the world.

- [Narrator] Inside
of the bunker,

a secret lurks in the bowels
of this defensive line.

Buried up to 180 feet

are a series of interconnected
tunnels so massive

it questions how they were
constructed in the first place.

- Imagine if you
had made it through

all that defensive concrete.

Well, it turns out that's
just the beginning.

What's beneath your feet

is a whole network of
underground tunnels.

It's an underground
city down there.

- It's extensive.

There's a lot of
planning and engineering

and building and resources and
thought that goes into this.

It's difficult to
wrap your head around

how they were intending to
basically live here, if need be.

- If you imagine that
you can go downstairs

and walk through these
tunnels for three or five days

and you will still not reach
another part of that system,

you can realize how huge it is.

- [Narrator] These
massive tunnels were
bored into the earth

by the company Siemens & Halske,

who had built the
Berlin subway system.

The tunnel system
impressively connects

to the hundreds of
bunkers above ground

and stretches for
miles underground.

- Imagine tunneling in
the 1930s under duress

and having this ambitious
scope and length of tunnels.

It changes that whole dynamic.

It makes a lot riskier.

- Tunneling in any
environment is challenging.

And the technology
that is available now

has advanced way more, and
it's still very challenging.

So, to think about
tunneling in the 1930s

and to think about the
length of these tunnels

and how deep they had to go

with the technology
that was available then,

it must've been an
insane amount of work.

- [Narrator] Even
more astounding,

these tunnels were
bored in sand.

- Tunneling in sand is
an unstable endeavor.

It's loose, it's not compact,
it doesn't self-support.

Not only did they have
to excavate the sand,

deal with that excavated
material, get it out of the way,

but they also had to
pump concrete down

to re-support these tunnels

so that they wouldn't
cave in on themselves.

- [Narrator]
France's Maginot Line

only contains six
miles of tunneling,

which connected to select
bunkers on the surface.

But here, the Festung tunnels
stretch for over 20 miles

and connect to every
topside bunker.

To top it all off, these
tunnels were outfitted

with an impressive rail system
that was entirely electric.

- When you understand there
were underground train networks

which connected at
least a few dozen

elaborate tunnel systems-

- If we imagine
the modern subway

with all those tunnels
and subway stations,

it's quite comparable, in fact.

In Warsaw, we had less subway
lines than in the Festung.

- [Narrator] This rail
line could transport troops

across miles of tunnels
to defend any location,

should an attack occur.

- This is the next level
of military defenses.

Talking about bunkers with
up to 10-foot-thick walls

with shafts running down
under the ground to 180 feet

to reach rail tracks
that allow you to travel

across 22 miles of
interconnected systems.

- If you can't get the food

and the resupplies
to the troops,

you're not really
gonna be effective.

And building an underground
electrified railway

was a great way for the Germans

to ensure those troops were
well-supplied, comfortable,

and made sure they had
everything they needed

to sit there for
literally months of attack

and not have any
real supply issues.

- In the underground
tunnels, there were storages,

bunkers, a lot of ammunition,
lot of food supplies.

So, for three months, they
can act in total autonomy.

- Everything you can
possibly imagine is there,

and you can come away from that

with an obvious sense of dread.

- [Narrator] These
tunnel systems

included their own water
reservoir, communication systems

linking the full
network of structures,

hospitals, and its own
dedicated ventilation system.

Over 20,000 troops
could be housed

in these underground tunnels,
where they had enough supplies

to last for up to three months.

- These structures,
while huge on the inside,

really aren't that
giant on the outside.

So, the attacking
force is looking at it,

going, "Well, that's
really not that bad."

I mean, this is totally
new to the world.

Nobody had built any
system of this size,

of this interconnected bunkers

that could house tens of
thousands of soldiers.

There was a lot of thought
put into this design

in order to maximize
its ability to defend.

- [Narrator] Germany
has spared no expense

in building these
fortifications,

and they've come
at a great cost.

- Unlike in later complex
engineering projects

of the Second World War,

the German Nazi regime have
no slave labor to build this.

You have to understand,
this is a project

costing hundreds of
millions of Reichsmarks.

This is one of
the biggest things

they'll do in 1930s Germany.

And it's all under the
nose of the Allies.

- [Narrator] The
Festungsfront defense line

is extremely
technologically advanced.

It requires a
specialized military crew

to effectively utilize the wide
range of devastating weapons

employed at the
bunkers and to operate

the complex systems of
rails and the tunnels below.

- In 1938, there was
many troops specialized

in fighting in such facilities,

very specialized troops
knowing the system,

knowing how to use
it effectively.

- [Narrator] This defensive
line would be insurmountable

for any invading forces,
but things were changing.

In 1938, Hitler
inspects the system,

and suddenly construction
comes to a complete halt.

- But why?

What possible reason
could there be

to just abandon such
a huge investment?

- What we see today is just
a piece of this whole system.

They didn't end up
finishing this project,

but they still achieved
so much in six years.

- [Narrator] If it
were to be completed,

this site would contain

nearly 13 million
cubic feet of concrete.

- That's just unimaginable.

- If we look at Yankee
Stadium, for example,

it would not be
nearly in that range;

maybe around 20,000
cubic meters.

Here, we're talking 360,000
cubic meters of concrete

that woulda been used had the
project gone to completion.

That's a lot of concrete.

- [Narrator] Why would the
Nazis put so much effort

into this massive system,

only to halt it before
it was finished?

In under six years, the
Nazis have managed to create

one of the most
technologically advanced

and powerful defensive
systems the world has seen.

Then, all of a sudden,
before it's completed,

Hitler orders it stopped.

Then, in May of 1940,
the Nazis invade

the Netherlands,
Belgium, and France

and introduce a new terror
to the world: the Blitzkrieg.

[explosions booming]

- Blitzkrieg is all about the
rapid advancement of troops

using a combined and
coordinated approach,

from the air and on land,

using tanks, infantry,
and mechanized vehicles.

- You throw everything at
one concentrated point,

and the enemy cannot stop that.

- No one had seen
anything like this before.

And it was very different
to the static warfare

that had played out during
the First World War.

- [Narrator] The shift from
static trench-based warfare

to the rapid
advancement of troops

leaves defensive lines like
Festungsfront in the dust.

- But it's actually
the Nazis themselves

that prove that this
First World War mentality

of static defense isn't worth
the paper it's written on.

In 1940, they carve
through the Maginot Line

like a knife through butter.

- World War II was itself
a revolutionary curve,

so defensive networks like that

became not exactly redundant,

but certainly not as impressive

as they were designed
in the 1930s.

- [Narrator] In spite of
its technological feats

and devastating armaments,

Festungsfront's importance
all but disappears.

- There's a ton of
resources poured into this

that never really
came to fruition.

It was almost a waste, in a way.

There was a lotta
planning and foresight

in anticipation of
what might happen here,

and it never came to.

- Constructing this site took
miles and miles of tunneling.

Tons of concrete and steel
needed to be erected.

A train line was built.

How on Earth did they
achieve all of that?

- It would be difficult
for any government today

to build one of these projects,

not only the science and the
engineering, but the cost.

In today's dollars, we're
talking billions of dollars

for a lotta these projects.

- The fortification
system has its place,

but it is very much
rooted, I think,

in the lessons of World War I

rather than in thinking
about how the next war

might be informed by these
game-changing technologies

that we start to see at
the end of World War I.

- [Narrator] Germany
continues to evolve

its military strategy.

And on June 22nd, 1941,

the Nazis would execute
Operation Barbarosa

and begin their charge
into Soviet territory.

- When you consider Blitzkrieg

and the speed at which the Nazis

sweep through the
occupied territories,

it's kind of obvious
that the Festung

should now become
all but abandoned.

Germany's ever-expanding borders

are now hundreds of miles away,

and Hitler is
feeling invincible.

- Germany's priorities shift

from building these
defensive structures

to an offensive posture,

both on the east and
on the Western Fronts.

- [Narrator] Festungsfront
is now considered

to be in safe territory

and it's unceremoniously
stripped of its
units and supplies

and left nearly derelict.

On July 15th,

less than a month after
invading Soviet territory,

the Nazis capture Smolensk.

- Germany is now practically
knocking on Moscow's door.

- [Narrator] But the
Blitzkrieg technique

reveals its limitations.

- Blitzkrieg is vulnerable,

and it's really
vulnerable to its assets.

It's vulnerable in the sense
that that emphasis on mobility,

on speed, means that
if anything goes wrong

to slow down that speed,

those forces are left
pretty ill-equipped.

That can turn into
a real liability.

- [Narrator] The
tides are changing,

and Germany will realize
that string of successes

in the east will
come at a heavy cost.

[explosion booming]

With their Blitzkrieg strategy,

Germany has driven their forces
deep into Soviet territory,

but they're brought
to a crushing halt

when they reach Stalingrad.

- But the tides are changing.

Suddenly, that German
advance is stopped.

And slowly at first,
but ever faster,

the Nazis are being pushed back.

- They're losing hundreds
of thousands of soldiers

across the various fighting
fronts between 1944 and 1945.

At Stalingrad alone,

the entire Sixth Army
is completely wiped out.

- [Narrator] Germany
quickly retreats

across its former
occupied territories.

Further devastating
Hitler's plans,

the Allies have landed
along the Western Front.

The walls are closing
in on Nazi Germany.

- Hitler realizes he's
vulnerable in his Eastern Front.

So, at the last minute,
he rushes to renovate,

to refit, to expand
this east wall.

- Even though it's unfinished,

could the Festung defenses
now prove to be the catalyst

to turn the tide back in
the favor of the Germans?

- [Narrator] The
Nazi regime diverts

as many resources
as it can to Festung

and prepares for battle,
but the Soviet army

will prove to be a
truly formidable entity.

- And it is an army
bent on revenge.

It's an army that wants
to exact a terrible price

for the suffering
of its own people,

and so it unleashes
fury, hell on Earth.

- I cannot imagine how
frightening it would be

to be living in the
eastern territories

and have the Red
Army come through.

It would've been the most
terrifying experience

of your life.

- [Narrator] As the
Soviet army closes in,

Festung prepares to see if
it can fulfill its purpose

to protect Berlin.

- Even though it was unfinished,

the Festung would've
been their ultimate test.

- [Narrator] But
what kind of forces

have been roused up by Germany

to fortify this
massive defense line?

- In 1945, Goebbels
and Hitler put together

what's know as the Volkssturm,

which is essentially
boys as young as 16

and men as old as 60

who are given obsolete
weapons or no weapons

and told to go out and
defend the German Reichs.

- German forces, they
had to improvise.

And they have no knowledge
about the system,

did not know how huge it is.

There was normally
equipment inside

that you could use to
defend such a fortress.

- In the world of engineering,

no matter what system or
machine or structure you build,

if it's operated by humans,

it's only ever gonna
be as effective as
the humans using it.

And if you can't supply it
with the skills that's needed,

then it's always gonna be
operated at suboptimal level.

- [Narrator] Despite
Germany's last-minute rush

to staff the Festung
defense line,

it's far too little
and far too late.

- The Red Army overran
it in three days,

which is really nothing
when you consider

the size and scale of
these fortifications.

- [Narrator] But because so
much of this defense line

is buried, it remains
a secret initially.

- Most of the Soviet
troops don't even know

that they make their way through

this huge fortification line.

- [Narrator] Original plans
for the Festung defense line

saw construction
continuing up until 1951.

Its already-impressive defenses

would've been made
even more formidable.

- At the end of this story,

you're just left wondering
what could've been.

Had the Festung been completed

and had it been manned with
fully-trained operatives,

might the outcome of the
war have been different?

- [Narrator] Ultimately,
the systems contained

within the massive
Festung defense line

are so sophisticated
that the Russians

and later the Polish
couldn't operate them.

So, instead, they
stripped the site

of the most valuable
metal and technology

and then abandoned the site.

A section of the
massive Festung tunnels

were even filled with waste,
acting as a trash disposal site

for the Polish
army in the region.

- Every element of the Festung
was high-tech on this period.

We have to realize
that these dragon teeth

is connected with
those hydrologic lines,

with those bunkers
connected to each other.

And as we see, it wasn't
also high-tech for the '30s,

of 20th century, but even
now it's really impress.

- [Narrator] Today, these
fortifications still stand

as a testament to their
over-engineered construction.

- They look like they
would have in 1944.

It's almost as if you
took a time machine.

- These bunkers have walls
that are nine or 10 feet thick.

It's just an unreasonable
use of concrete in a wall.

It's just a significantly
heavier purpose

than just resisting
environment loads.

- It's an immense
amount of work.

The scale of it, to
me, is impressive.

- It's like a rabbit
warren, it really is.

It's kinda this underground
endless array of technologies

and building capacities,
and it's scary.

- [Narrator] The Nazis built

one of the most advanced
defensive lines on Earth,

one that outlived its own era.

Ironically, when it mattered
most, it was rendered useless.

But the ghosts of this complex
hint at what could've been

had events played
out differently.

[suspenseful orchestral music]