Original subtitles

Beneath the densely woven forests of northern Poland,

a jagged scar etches its way across the landscape.

50 kilometres of weathered concrete carves

a path through the waters of Lake Mamry to

the open plains of the Baltic Sea -

a forgotten canal branded by a fallen empire.

This imposing structure bears

the ominous signature of Nazi Germany -

a testament to the imprint they had on this region.

Preceded by decades of failed attempts,

a fragmented foundation lay dormant until Hitler seized

the chance to revive this waterway into

a monument of totalitarian might.

The Masurian Canal, once finished,

would be a symphony of steel and concrete,

bending the waters to the will of the Reich.

There are thousands of tons of concrete in this.

It is difficult terrain to build in.

This was a complete system, designed to dominate

the waterways of East Prussia.

This will become one of

the largest engineering projects that

the Nazis will undertake in East Prussia.

Capable of carrying ships of up to 240 tons,

this ambitious waterway would link

the secluded Masurian lakes to the open sea,

forging a vital artery

of commerce through German-controlled territory.

Though built under the facade of economic progress,

this relic of Nazi engineering may harbour a far darker secret.

Why did Hitler want to resurrect this engineering project?

What potential advantage or benefit did he see in

an abandoned waterway?

To this day, there's still speculation as to

the true purpose of this waterway.

Why was its construction kept a secret?

And in the end, why was it all just forgotten?

1933, East Prussia,

a lonely German enclave isolated by foreign borders.

After World War I, Prussia was divided

and parts of its territory were given to Poland.

East Prussia became

a territory of Germany that was non-contiguous.

The only ways to access it from

the rest of Germany were by land through

the Polish Corridor, or via the Baltic Sea.

Comprised largely of agricultural lands

and lush mixed forests, its northern region also boasts

a rich inland reserve of freshwater lakes.

The Masurian Lakes District

of northern East Prussia has about 2,000 lakes.

It covers an area of roughly 52,000 square kilometres,

similar in size to a country like Costa Rica.

It extends eastward from the lower Vistula River to

the modern day border between Poland

and the Russian exclave of Kaliningrad.

However, this region finds itself in a precarious position,

located in an outpost of Germany that's deeply vulnerable

to external interest.

As the Nazi Party ascends to power,

the Masurian Lakes and the Greater East Prussian

stronghold take on new significance.

It is not just a border that Germany needs to protect,

it is also a buffer zone between Germany and Russia.

It is territory which can be used

for infrastructural developments such as factories,

armament factories, that would help Germany in its war effort.

And then finally it is geo-strategically important

for Germany for the logistical movement of its troops.

For any kind of operation launching into

the Soviet Union, it's a good staging point.

It's also a good staging point if they go to war with Poland.

After Hitler comes to power, the Nazis begin

to transform East Prussia from

agricultural heartland into more of an industrial area.

Yet to unlock the vast potential of this wooded region,

an extensive overhaul of infrastructure would be required -

a web of railways, roads and robust waterways.

As Nazi planners survey the East Prussian landscape,

their attention is drawn to a winding trail

of abandoned concrete beds snaking through the terrain -

the remnants of the Masurian Canal.

These sprawling foundations were the beginnings of

the Masurian Canal,

a transportation project that had broken ground decades earlier.

The plans for this waterway was to connect

the Masurian Lakes with the Baltic Sea.

By the dawn of Hitler's reign,

the art of canal engineering was well-established across Europe.

The Reich's ambitions, however,

would breathe new life into this age-old technology,

etching a symbol of their empire into the earth.

Canals are a really important part of our

transportation infrastructure.

They allow marine traffic to traverse

a shorter distance between different bodies of water,

different elevations of water.

It's a very difficult construction to do,

but it can be very meaningful in allowing communities

to evolve and flourish, and it is a critical piece

of infrastructure to drive that growth.

The first proposals for the Masurian Canal can be traced back to at least

the 18th century, the golden age of waterway construction.

During this era, administrators under King Frederick

the Great of Prussia seek to establish new channels of trade

and transport across their kingdom

and note the potential of this expansive lake district.

Between the 17th and 19th centuries, Europe experienced a canal age,

a period of increase in the building of these waterways,

because they'd become the fastest means

for long distance travel and transport.

By the 19th century,

Europe has an intricate network of canals that connects

the English Channel with the Atlantic Ocean,

with the Mediterranean Sea.

Canals really become the veins through which

the lifeblood of European progress flows.

This idea, however, would lie dormant until the mid-19th century,

when the notion resurfaces as the Allenburger Canal Project,

a 50-kilometre long route capable

of carrying cargo ships into the heart of the region.

This proposed channel would allow freighters to navigate

an elevation change of over 100 metres

from the coast to the interior -

a vertical feat that would require the incorporation of

a crucial mechanism.

The elevation difference between the Baltic Sea

and the Masurian Lakes is 111 metres.

That's about the height of Big Ben.

By the end of the 19th century,

canal construction is facing competition from

the advancements in steam locomotives.

The canal proposal and the land it would traverse undergo

a number of changes in the following years.

As the region is absorbed into the German Empire,

revisions reflect new priorities, one of which sees

the initially promising inclined plane design replaced by

a more conventional yet reliable lock mechanism.

An inclined plane is simply a mechanical method

for moving boats between different elevations.

Using a system of cables and powerful engines and brakes,

that boat is either raised up or lowered down the incline.

Lock gates have been used to raise

and lower boats along waterways for thousands of years,

and the theory behind them is actually very simple.

If a ship is moving downstream to enter the lock,

it goes through the entrance gates where

the lock gates close behind it,

and it is now in a watertight chamber.

A valve is then opened,

which drains that water inside the chamber

and lowers the ship.

Once lowered, the exit gates open

and the ship can sell out through it,

now at a lower elevation.

And, if it needs to go the other way,

ie back up, you just reverse the process.

By the spring of 1911, after decades of deliberation,

the project finally navigates the maze of bureaucracy

and emerges with official authorisation

and a budget of 15 million marks.

The sound of machinery breaks the silence of

the East Prussian woodlands,

and the vision of this enormous hydro-course begins

to take physical form.

But, as workers toil to reshape the terrain,

a distant rumble grows on the horizon,

one that would soon reverberate across the continent

and bring construction to an abrupt halt.

1914, a young Adolf Hitler leaves the streets of Vienna for

the German city of Munich,

a place pulsating with nationalistic fervour.

Swept up in the patriotic tide,

Hitler disregards his foreign status

and enlists with the Bavarian Army.

The Great War has begun,

and he eagerly heeds the call to arms.

Hitler's involvement in the First World War is

a seminal moment in his life.

Before he enlists in the Bavarian Army,

he is a failed artist, he is a man without purpose.

His involvement in the First World War gives him

purpose for the first time in his life.

This is the most positive,

formative experience that Hitler had

in imbibing German nationalism, patriotism,

fighting alongside other German soldiers

and developing that sense of military honour,

it's a very transformative experience for Hitler.

As Hitler joins the front line in Belgium,

the German Empire faces a grave threat from the East.

The Russians have set their sights on Berlin,

but, before they can march on the capital,

they first must contend with their enemy's nearest frontier,

East Prussia.

In this outlying province, the Masurian Canal sits unfinished

and exposed - a testament of German engineering,

now vulnerable to the tides of war.

As the summer of 1914 harrowingly unfolds,

Russian forces surge across the border

and the tranquil lake district is transformed into

a deadly battleground.

The province of East Prussia, on the periphery of Germany,

is actually the only part of

the German Empire itself that saw direct combat during World War I.

By this time, the Masurian Canal is already

three years into construction,

but only a tiny proportion of earthworks have been completed.

And whilst by today's standards that speed

of progress might seem incredibly slow,

you need to understand the challenges that were presented

by the rugged and remote terrain it was attempting to cross.

Though the Germans hold their ground in East Prussia,

their leaders will ultimately

surrender after years of combat against

a powerful coalition of enemies.

In the war's aftermath,

the defeated Weimar Republic is left to count its losses.

As the nation struggles to rebuild from

the ashes of defeat, work on the Masurian Canal resumes.

However, in just a few years,

the Republic's withering economy once again brings the project,

along with many others, to a standstill.

Eventually, this stalled mega structure will fall

into the hands of a burgeoning radical

intent on transforming the nation.

1934, under Hitler's Germany,

labourers are sent in droves to

the forests of East Prussia to resurrect

the failed Masurian Canal.

And soon an "Arbeitslager", or labour camp,

is erected to accommodate the growing pool of local

and conscripted workers.

A sense of urgency lingers in the air -

Nazi administrators wish to see the canal completed by

the turn of the decade.

There seems to be a really aggressive push

to resurrect this canal project.

Why is it that there is such focus placed on this undertaking?

So there's many different objectives that could have been at the back

of Hitler's mind.

The one that they probably started off with, before even

the beginning of World War II,

was to kick-start economic growth and development.

A decade earlier, the toll of Germany's surrender

had severely deteriorated the economy.

Runaway inflation had plummeted the mark to absurd lows,

with citizens requiring wheelbarrows of money to buy

a single loaf of bread.

Following their reluctant signing of the Treaty of Versailles,

effectively ending the war,

the Weimar Republic was broke and defenceless.

The Treaty of Versailles is

the peace treaty that Germany is forced

to sign when it loses the First World War.

It sets out a number of terms and conditions,

and these include the loss of territory,

the loss of their army,

which has to be limited to a very restricted number of troops

and cannot be developed significantly.

Germany is required to pay significant

reparations that end up crippling its economy.

The "stab in the back" myth is this idea that Germany didn't actually

lose the war on the battlefields,

that it was stabbed in the back by a group of Jews,

socialists and pacifists.

And it is a myth that is perpetrated by

the German high command to save face -

the idea that Germany didn't lose the war.

It is a total myth, because Germany did lose the war.

There's absolutely no doubt about that -

Germany signed the Armistice because it couldn't keep fighting.

Hitler seizes the simmering resentment like a weapon,

ascending the public stage as a leading member of

the nationalist Nazi movement.

His fiery call for a New German Order

herds thousands to his support.

Although the Nazi Party forms in the early 1920s,

it isn't until the late 1920s, and in particular when

the Great Depression really sets in in Germany after 1929,

that we see a significant rise in

the popularity of this political party.

The party's radical platform finds growing appeal among

a populace that's disillusioned by the failures of

the Weimar Republic.

Soon, the Nazis become the largest party in the Reichstag,

and Adolf Hitler cements his seat as the absolute dictator of Germany.

His initial ambition is to rebuild Germany economically,

and for him, the way to do that was to create jobs.

How do you create jobs? You launch a whole lot of

infrastructure projects all over Germany,

and you try to start building up the army,

go on the defensive,

protect the German economy in order to rebuild the country.

Under Hitler's iron-fisted rule, every corner of

the Reich sees dramatic transformation,

as a series of aggressive policies

and infrastructure projects are hastily set in motion.

In the enclave of East Prussia, change is already well under way.

At the orders of the provincial Nazi leader, Erich Koch,

agricultural lands once tilled by independent farmers

is collectivised and the region moves towards

mass industrialisation.

Erich Koch is the regional leader

of East Prussia when Hitler takes power.

Erich Koch uses these emergency relief funds

to really establish industry in East Prussia.

Koch is quick to tout his success, asserting that his policies have

eradicated unemployment in East Prussia -

a feat that garners widespread acclaim throughout the Reich.

Koch proclaimed that he had

eradicated unemployment in East Prussia,

and this became a powerful tool of Nazi propaganda -

Hitler would tout that.

And by claiming to have eradicated unemployment in East Prussia,

Koch became famous - he was the recipient

of widespread acclaim throughout Nazi Germany.

Soon the unfinished Masurian Canal,

previously left abandoned to the forest floor,

resurfaces yet again -

the perfect foundation for a network of maritime traffic.

In 1934, Hitler's first year as Fuhrer,

his party approves the continuation

of this crucial bridge to the Baltic,

with a commitment of 19.5 million Reichsmarks.

Connecting the Masurian Lakes to the Baltic Sea,

opens up a new artery of trade and transport for the Germans.

But, maybe there were other reasons, beyond economic reasons,

that Hitler wanted to complete this canal.

From what we know about Hitler today,

it's very likely there was an ulterior,

perhaps darker motive behind this project.

In the bug-infested backwoods of the Masurian Lakes,

labourers rush to advance

the Masurian Canal's long-awaited 50 kilometre span from Lake Mamry to

the Lyna River,

where vessels could then navigate onwards to the Baltic Sea.

The timeline from 1934

to 1941 that Hitler imposed on

the project to be completed by is incredibly ambitious.

It would take years of planning

and design to make this work - it's a giant project.

Though having sat dormant for a decade,

its unfinished contours had slowly been reclaimed by the elements.

Years of neglect had taken their toll,

and, before Nazi shovels can carve new ground,

the existing foundation must be reassessed.

The first step of any construction project is actually

to build infrastructure just to get to the site,

let alone making sure that you have materials available on site to build

the things you want to do.

We're talking about excavators,

the potential blasting if they hit rock.

That is just an incredible undertaking.

To address a project of this scale, planners pull hands from

the consortium that would become known as Organisation Todt.

Organisation Todt is an extensive civilian

and military labour force.

This organisation is responsible for building roads,

railways, factories, and fortifications across the Reich.

Organisation Todt will be the largest workforce in Germany.

Eventually, they'll have over a million,

I don't want to say employees

because they include slave labour, conscripted labour,

foreign labour and prisoners of war,

but they will have over

a million people slaving for them indeed.

The task ahead is monumental and the specifications daunting -

a 2.5 metre deep gash in

the earth that weaves over 50 kilometres through

a dynamic landscape.

At its lowest point, the canal bed would span 13 metres wide.

And, once eventually filled with water,

the breadth from bank to bank would stretch 23 metres across.

The canal itself would then be accompanied by hundreds

of subordinate structures such as siphons,

tunnels, bridges, outbuildings, reservoirs,

and even small passages for local wildlife.

And the challenges extend beyond sheer size.

The Masurian landscape is a mosaic of rolling hills

and marshy lowlands.

Cutting through this unpredictable

terrain demands constant adjustments.

To smooth its course,

the Nazis create massive embankments along the spine of the canal.

Certain sections of a canal construction will need

the use of embankments, which are essentially lengths

of compounded raised earth that are used

to avoid any significant height fluctuation for the waterway.

And some of the embankments on

the Masurian waterway measured up to 15 metres high.

That's a lot of earth to build up.

From the sprawling earthwork arises

a chain of ten reinforced concrete locks,

massive mechanisms used to drop

and elevate ships along their route to and from sea.

There are ten locks across this canal,

and they categorise those locks based on

the elevation change from eight metres of elevation change all

the way upwards to 30 metres - that's a really big distance.

The manual capabilities

of these locks is crucial in case there is some kind

of malfunction or any kind of power outage.

One end of the canal touches the edge of Lake Mamry,

in the heart of the Masurian Lakelands.

Here, vessels will pass through the grandest feature of

the entire system.

The scale of the Lesniewo Upper Lock is a true sight to behold.

It is the king of this canal.

The length of its chamber is a whopping 46 metres.

Working in tandem with its sister lock,

the Lesniewo Lower Lock,

it can lift or lower ships 33 metres.

That's about the height of a ten storey building.

Inside the lock's chamber,

the Nazis also built a labyrinth of rooms to house

the mechanism for operating the lock.

Now known as the Lesniewo Upper Lock,

Schleusen Furstenau is

the crown jewel of this ambitious project,

a showpiece of the Nazi regime,

its towering concrete facade,

emblazoned with the Imperial Eagle, the Reichsadler

and the swastika of the Third Reich's coat of arms.

The financial investment of this canal is staggering.

Building a single kilometre of

the canal costs 800,000 Reichsmarks,

which is the equivalent of $7 million today.

In fact, it is second only to the development of

the autobahn in East Prussia.

This canal has sort of had a stop/go history,

so it seems now with the Nazis in power,

that for the first time, the canal will actually be finished.

For some time,

it seems the Nazi promise of new infrastructure

and economic rebirth in East Prussia is coming to fruition.

Between 1933 and 1936,

employment in the construction industry across

the Reich nearly triples.

The Masurian Canal is poised to be a testament of progress.

But a dark undercurrent runs beneath the surface.

As the decade lingers on, Hitler's true ambitions,

and perhaps the ultimate purpose

of this inland waterway will soon be revealed.

This canal doesn't feed any big city,

so what is it about this region that lures the intrigue

and the interest of the Nazi leadership?

For all its power and scale, the construction of

the Masurian Canal is shrouded in secrecy.

Only high ranking loyalists are privy to

the true extent of the plans,

leaving many to wonder about

the real purpose behind this massive undertaking.

In the late 1930s,

the canal does not appear on any maps.

You don't want it advertised, or certainly

identified where exactly it is.

The closer we get to the War,

the more it seems this canal is being hidden.

But, the completion of the canal may be far more than

an economic endeavour -

perhaps this waterway is

a key piece of Hitler's grand political puzzle.

Could this canal be used to serve areas that are being used

for clandestine military operations?

Is it possible that this remote,

isolated outpost is in fact a launchpad

for Hitler's vision for "Lebensraum"?

Lebensraum is a very old concept in German history -

"living space".

It entails this idea that

the German people should take over essentially Eastern Europe,

all the way to the Ural mountains which divide Russian Asia

from European Russia.

Beneath the shadows, Hitler is rolling out

plans that brazenly defy the punitive Treaty of Versailles.

Under the guise of performing routine maintenance

on his existing fleet, he secretly approves

the expansion of the Navy,

projecting the construction of battleships,

destroyers, and submarines,

all in direct violation of the Treaty's terms.

His aim is clear, to transform his allowable,

small defensive force into

a formidable military capable of offensive action.

This marks the first step towards building the fearsome Wehrmacht.

Hitler was always looking for ways

to re-militarize in defiance of the terms of

the Treaty of Versailles

and take steps to create a powerful German military,

the Wehrmacht, Germany's unified military made up of the Heer

or the Army, the Kriegsmarine, the Navy,

and the Luftwaffe, the Air Force.

Hitler is essentially mobilising

the entire population of Germany to be on a war condition.

September 1st, 1939,

the fragile peace in Europe abruptly implodes as

German forces unleash "Fall Weiss",

a devastating blitzkrieg across the Polish border.

As Luftwaffe planes darken the skies over Warsaw

and Panzer units thunder into the country,

Poland finds itself surrounded by Hitler's relentless war machine.

Within days, their defences crumble under the onslaught

and the world watches in horror as

the once sovereign nation is torn apart.

This signals the beginning of

the deadliest conflict in human history -

the Second World War has begun.

Hitler had been preparing the country for greatness, essentially.

Ever since he'd taken over power, he was trying to rebuild Germany

and help Germany regain its foothold in Europe.

As Hitler plunges Europe into the Second World War,

every single strategic resource that Germany has becomes essential

for its war machine.

And this could potentially extend to the Masurian Canal.

Yet, as the conflict spreads across the continent,

priorities shift dramatically.

All attention pivots to the immediate exigencies of warfare.

In the remote reaches of Masuria,

work on the canal is consequently paused, as resources

and labour are redirected to a more pressing need in

the Eastern Corridor.

It makes sense that the workers who were building

the Masurian Canal at the time were redirected

to start building the Wolf's Lair,

because that was a military headquarters,

and it was extremely essential for Hitler,

because that's where the entire war plan was created.

And it needed to be in a place that was well-protected,

in a place that was well-hidden, and a place that was well-supplied.

Around 20 kilometres southwest of Lake Mamry,

nestled in the wilds of Gierloz,

a grand undertaking is set to outpace the canal.

Utilising the natural barrier of the Masurian Lakes,

builders hurriedly work at constructing

a 6.5 square kilometre compound to house

the eastern headquarters of the Fuhrer himself.

Aptly named Wolfsschanze, or the Wolf's Lair,

this will become the heavily fortified nerve centre from which

Hitler will orchestrate all military operations in the eastern arena.

All these resources that are being deployed to the canal,

suddenly those resources are now cut back to build the Wolf's Lair.

This complex of bunkers that is enormous,

that is as big of an engineering enterprise as,

you know, a few miles of canal.

Additional subordinate headquarters associated with

the Wolf's Lair are dispersed throughout the region.

The largest of these satellite compounds sits on

the western bank of Lake Mamry.

Designed as a base for the Wehrmacht's Supreme Army Command,

the Oberkommando Des Heeres.

Construction of the sprawling settlement known as OKH Mauerwald

is entrusted to the Organisation Todt workforce

that has previously carved the bulk of the Masurian Canal.

Within a single year, they're tasked with erecting one of

the most impressive military bases

for Chief Staff that East Prussia has ever seen.

Mauerwald translates to "Wall Forest"

and is essentially what it sounds like -

it is a wall of concrete in the middle of the forest.

This is a place that has its own power grid,

drainage system, communications network,

and even a hospital.

And, at its busiest time during the war,

there are over 1,500 officers living and working here.

Thousands of labourers are employed over

the next four years to build this massive complex.

A common practice employed by

the Nazis in their massive construction projects was

to shuffle workers out.

And this was in the interest of security -

there wasn't anyone who had worked on

a project from beginning to end and knew its full scope

and all of its dimensions.

Both Mauerwald

and the Wolfsschanze were also camouflaged as chemical plants.

Nobody realised that there was kind of

a military significance to the Mauerwald.

The operations at Mauerwald are shrouded in protection.

The site itself is a fortress of secrets.

Access to the compound is strictly controlled,

connected to Wolfsschanze only via a single rail line.

Interestingly, Mauerwald is located along

the southern edge of the Masurian Canal.

Situating this major military base so close to

the canal does suggest that the purpose of

the canal from day one was not just economic.

And obviously, in war, control of the waterways is paramount.

The Germans build

a number of these fortified command posts in East Prussia,

because they are planning an invasion of Eastern Europe.

In August 1939,

Hitler and Stalin sign a non-aggression pact.

This gives Hitler the green light to start World War II.

It's also very interesting,

because what it means is between the invasion of Poland

and Operation Barbarossa, Nazi Germany and

the Soviet Union are essentially allies.

It means that after Hitler's conquered Poland, he knows he has

a friendly power on his eastern border,

so he can turn his full attention to the West.

Hitler sets his sights on knocking Britain out of the war,

and he tries to do this through the Battle of Britain.

He fails - Britain wins the Battle of Britain.

So, then Hitler turns his attention to his ultimate goal,

which is the defeat of the Soviet Union.

As the war brutally treads on, steel is forged

and machines take shape across the Reich.

Envisioning an ocean fleet capable of maritime dominance,

Hitler calls for the widespread production of

the nation's most ferocious naval weapon, the U-boat.

Arguably, the U-boat is the German's most powerful naval

weapon of the 20th century.

Initially used in the First World War,

these vessels could dive to a depth of around 50 metres

and had a range of 40,000 kilometres.

Because the U-boat can travel long distances without being detected,

it allows the Germans to be able to circumvent Allied blockades.

Lurking beneath the waves of the Atlantic,

this silent predator gains notoriety for its ability

to strike from the depths without warning,

leaving a trail of destruction in its wake.

In the First World War alone,

German and Austrian U-boats sank around 8,000 Allied merchant

and warships many times their size, claiming the lives of tens

of thousands of sailors in the process.

Submersible vessels experience an incredible amount

of pressure as they dive deeper into the water.

The U-boat design employed

a new alloy that was stronger than previous steels

and allowed them to go deeper

and to resist that pressure and to be safe.

During the Second World War,

the Nazis continuously developed the design of the U-boat

and at one point incorporating the G7e electric torpedo.

Whilst it sacrificed some speed

and range compared to its steam powered counterpart,

it no longer had the telltale stream of bubbles behind it,

which made it much more difficult to detect.

At the start of the Second World War,

the Kriegsmarine has just 46 operational U-boats,

but by 1941 that number increases to 365.

Producing U-boats is very challenging.

Not only are they a large machine that takes

a lot of work to actually build them,

the U-boat construction is being targeted by the Allies.

And the reason for that is because they are one of

the biggest threats that the Allies face.

The Battle of the Atlantic is a life or death struggle

for the continued ability of Britain to resist against the Nazis.

If you were looking to build up the capacity

of your Navy, away from any external prying eyes,

there's probably no better place to do it than away from

the coast in this remote forestland.

And, through the canal,

with the potential to have access to the open water,

it's almost the perfect place to set up a secret shipyard.

Some say the canal may be intended to service

a secretive U-boat shipyard that

allows easy access from German territory to

the Baltic Sea, where vessels could then navigate onwards

to cause devastation in the Atlantic.

The canal is wide at certain areas,

and that's a critical design aspect.

These widened areas allow for a larger turn radius of up

to 40 metres - that is the turn radius of a smaller U-boat.

There is a big issue with that idea -

the canal is only 2.3 metres deep,

while the draft of a U-boat is over four metres.

Putting it simply, a U-boat could not sail through that canal.

However, as the Kriegsmarine scales back manufacturing from massive

shipyards to smaller factories that produce prefabricated parts,

the feasibility of work along the canal remains.

The Allied bombing campaign really undermines

Germany's war economy,

as it forces them to make radical changes

to how they're producing war machines.

They suddenly now have to build them in

heavily-fortified factories and then

bring them all together for assembly.

Prefabricated parts can be barged out, you know,

hide the prefabricated factory outside

of occupied Prussia.

If one gets bombed out,

they can turn to another factory for the parts.

Could Mauerwald have served a dual purpose,

not only as a command centre,

but also a cog in the machine of the Nazi war effort?

The function of most of the buildings at Mauerwald

are known to us today, but some still retain an air of mystery.

Buildings 11 and 12 are a little bit suspicious.

They're really big - they're 13 metres by 21 metres,

and they were purported to be a boiler room and a power plant.

These buildings are way bigger than what would be needed

for those utilities.

It might have been built for something else in mind.

Was there a secret shipyard for building U-boats,

or for making components for U-boats in

the Masurian Canal? We don't know.

But if a secret U-boat shipyard or a factory did exist,

where along this canal could it have been?

As the war rages on,

work on the Masurian waterway is slowed to

a near halt by 1941.

But this vast structure will soon find

a new purpose not as a transport route,

but as a strategic barricade in yet another deadly offensive.

June 22nd, 1941,

more than three million Nazi soldiers are quietly amassed along

the 2,900 kilometre border between the Reich

and the Soviet Union.

At the utterance of a simple command,

they blazed forward in a brutally deceitful attack -

Operation Barbarossa.

When Hitler then defies the non-aggression pact

and opens up the Eastern Front with Operation Barbarossa,

I think his calculation was that this would stunt

the Russians and would give Hitler

the edge going into the war against the Russians.

Backed by thousands of tanks and aircraft,

the Germans steam-roll east,

swallowing vast swathes of land,

crushing the ill-prepared resistance

and unleashing a conflict that would ultimately decide

the Second World War.

Operation Barbarossa is arguably

the biggest strategic blunder that Hitler makes during

the Second World War.

He hasn't actually finished his war in the West,

because Britain still exists.

And, so what he does is he condemns Germany to fight

a war on two fronts.

OKH, German High Command, becomes one of

the most important units during the planning of this operation.

The location of the Wolf's Lair and Mauerwald allows Hitler

and his generals to closely monitor what's happening

in their fight against the Soviet Union.

Operation Barbarossa ushers in a new chapter of

the war, as Nazi forces relentlessly push into

the Russian countryside, their sights set on Moscow.

Yet despite their meticulous preparations,

the invasion is a gamble.

And, in December of 1941,

after months of successful German advances,

the Red Army unexpectedly turns the tide,

forcing the Wehrmacht into a steady retreat.

Though construction had already stopped,

the Masurian Canal was around 90% complete

and virtually filled with water.

As the Germans retreat

and the Soviets advance into Germany proper,

the Germans are forced to turn everything

and anything into a defensive line.

And so the Masurian Canal becomes part of that defence.

And what you see is the canal is being used by

the Germans to try and halt the unstoppable Soviet onslaught.

And as part of that, they're actually destroying parts

of the canal, including bridges, to try and do anything

to slow down the Red Army's advance.

But this hastily cobbled defensive line,

an act of desperation in the face of defeat,

is not nearly enough to stave off the oncoming attack.

A tide of Soviet steel and determination pours westward,

fuelled by the blood of millions and the support of Allied resources.

City after city falls,

each bringing the roar of Russian tanks closer to

the heart of the Third Reich.

By May 1945, the Soviets seized Berlin,

and the war in Europe is finally brought to an end.

At the end of the war,

Josef Stalin meets with American President Harry Truman

and British Prime Minister Winston Churchill to decide

the fate of Germany.

They sign the Potsdam Treaty,

which divides Germany between the superpowers.

East Prussia is divided into two parts.

The majority is annexed by Poland,

and the remainder goes to the Soviet Union.

Poland and the Soviet Union find themselves in possession of

a regime's scattered remains across East Prussia.

The two powers divide the course of

the unfinished Masurian Canal between them.

Roughly 20 kilometres fall under Polish control,

while the remaining 30 kilometres becomes Soviet territory

with five locks in each section.

However, this partition does little to breathe new life into

the long neglected project.

Neither Poland nor the USSR possesses the resources or

the will to complete the canal's construction.

The grand vision of a navigable waterway connecting

the Masurian Lakes to the Baltic Sea,

and the secrets it once contained fades into obscurity,

overtaken by the pressing demands of the postwar era.

The fact that the canal does not get much use during

the war means that perhaps it did not meet its full

strategic potential.

Today, the canal is in a state of disrepair and decay.

A lot of the elements were either destroyed,

deteriorated, filled in.

It is not a functional structure.

Much of the equipment from the lock gates has been looted,

rendering them completely inoperable.

There's still a lock that has a kind of a shadow of

the old eagle Nazi symbol,

leaving this kind of imprint of its Nazi history to this day.

Seeing this intimidating Nazi symbol on this imposing feat

of engineering would really drive home

to anyone passing through,

this regime has built something impressive -

they are leaving their mark on the landscape,

they are a force to be reckoned with.

What's interesting here is, as they were taking off

the actual emblem, it fell into the water.

So, it poses this interesting question,

is it actually still in the canal?

Though seemingly forgotten, the Masurian Canal

and its neighbouring base have since been reclaimed by nature.

Their once formidable concrete shells softened under

a veil of moss and leaves.

These hollow skeletal remains,

once bustling with the frantic activity of warfare,

now stand as nothing more than a haunting monument in

a landscape transformed by the dark tides of history.

We have to wonder what the true intent was for this canal.

Why was its construction kept secret for so long?

And, more importantly,

how would the course of history have changed had

the canal actually been completed and that access to

the Baltic Sea had been opened up?

Subtitles by Red Bee Media