Original subtitles

I'm James Holland, and one of the things that's always really fascinated me

about the Second World War is the interplay between man and machine.

In this series, I'm going to go inside the Nazi war machine.

Travelling across Europe, I'll explore the extraordinary machines they produced

and uncover rare archives to understand who built them, how they evolved, and

why they're technically brilliant designs.

were militarily flawed.

The magnificent fighter planes no rookie could fly.

You know, the first time you fly a Messerschmitt 109, you just have to take

leap of faith.

The power of the panthers. If I had come up against this, I would have been

terrified. But I'm about to learn one of the biggest cons of them all.

The weapons that couldn't cope with mud or sand.

Wow. It's got... So little kick on it. And you hit the target, I'm proud about

you.

The U -boat that were floating bomb.

That was a suicide command.

Absolute horror.

A journey through the heart of the Nazi war machine.

In this episode, I'll be going to the depths of the Wolf Packs, Germany's U

-boat arm, a force that threatened Britain's survival like no other.

I'll be seeking out what made them such a menace.

The U -boat armies could have just wreaked havoc with the Allies.

They did play havoc.

And I'll be exploring the extraordinary and game -changing submarine, the Type

21. We are not talking about evolution anymore. That's a revolution.

And how they held the key to the outcome of World War II.

At the start of the Second World War, Britain ruled the wave.

The Royal Navy was the largest and most powerful seaborne force in the world,

built to protect its empire and to defend its nation.

It was a power Adolf Hitler

had to defeat if he had any chance of winning the war.

And there was only one way to do it.

Britain is an island nation, and it's almost entirely dependent on supplies

coming from across the sea.

If you manage to cut that supply line, then you've won the war.

That, at least, was the strategy being pushed by Adolf Hitler's U -boat chief,

Vice Admiral Karl Dönitz.

A U -boat commander in the First World War, Dönitz knew firsthand how even a

small fleet of submarines could land a killer blow against the Allies' vital

supply line.

But Hitler doesn't really seem to understand this. You know, he's a

continentalist. He's a landlubber. And this is because Germany is stuck in the

centre of Europe. It does have a coastline, but it's very small.

And the German way of war traditionally... has been to fight on

overwhelming firepower at the point of impact.

Germany has developed blitz warfare, mechanized warfare, armies on wheels,

juggernauts to crush everything before them. Come the start of the Second World

War, this is how Hitler intends to do it again, using firepower and burgeoning

air power to do the hard yards.

Sea power is something he just doesn't really get.

His notion of a navy was a grandiose fleet of massive battleships that could

take on the Royal Navy on the high seas.

After all, where's the fun in launching U -boats when it could be smashing

champagne bottles against giant battleships?

By the outbreak of war, Dönitz U -boat fleet was woefully small.

Just 62 vessels and a mere 3 ,000 men.

This beast was the backbone of the fleet, a Type 7C, and it's the first

going to look at in some detail.

The Type 7s were based on First World War designs and built in shipyards in

Bremen and Kiel.

Unlike its predecessors... It carried new sonar equipment, which greatly

improved its ability to search out enemy shipping.

It was a medium -range combat submarine, 61 .7 meters in length and 6 .2 meters

wide, and carried a crew of 44.

Powered by two 1 ,400 -horsepower diesel engines, backed up by a couple of

electric motors, it was armed with five torpedo tubes and a variety of top

-mounted flak guns and cannons.

It could travel at 17 knots on the surface, but little more than walking

when submerged.

This one is U -boat 995, now permanently berthed in the Baltic port of Labu in

Germany.

I'm on board to get a sense of the impact of this vessel on the war, and

was like to be at sea on the Type 7.

Oh, this is a bit of a tight squeeze.

You know, I'm really not sure how much I'd have fancied going to sleep with a

massive great torpedo above my head.

It makes you realise just how cramped these Type 7 U -boats were. You know, it

was a terrible place in which to exist.

Lots of men on top of one another.

hardly any fresh water, so you couldn't shave, you had to grow a beard, and

you'd be away for weeks at a time. The smell on this place must have been

absolutely horrendous.

Sweat, oil, rotten food, a really physically incredibly tough

environment in which to live and try and fight a war.

The U -boats lie in waiting.

Four, five and six of them together.

Working in flotillas.

Operating in wolf packs, the U -boats targeted Britain's lifeline.

The merchant ships supplying goods and materials from the United States and

Britain's colonies around the world. If we cannot bomb them out, then we will

starve them out.

The wolf packs were staggeringly successful.

Between July and October 1940,

The U -boats alone tanked nearly 1 .5 million tons of shipping.

They will stalk a convoy for days at a stretch, fighting their time until the

chance of wind and weather offers the fattest prize to their torpedoes.

This was a mammoth achievement, which cemented the U -boat's reputation as the

undetected superweapon the Allies desperately needed to destroy.

This is their song.

We're sailing against England.

For Admiral Karl Dönitz, using his crews to starve Britain into submission

remained the key to winning the war.

But without Hitler's full backing, he had a problem.

He didn't have enough boats, and he didn't have enough men.

To help me understand Hitler's failure to grasp the potential of the U -boat,

I've been joined in U -boat 995 by the historian of the German Navy

Dr Jan Witt.

One of the things I find just so extraordinary is, because Britain's an

nation, everything, everything it needs for war has to come through the

Atlantic. So if you can stop those supply lines, you're well ahead of the

So why is it...

that Germany starts the war with a U -boat arm which is just 3 ,000 men

Very simple to answer, because only in the early 1930s they started to build

up, at first in secret, then also openly.

But it takes a long time to build up a new U -boat arm

from scratch.

And so they could only reckon that these U -boats would be available in late

1940, early 1941.

So you have always this kind of delay.

But as Hitler is very, very aware, you know, the whole German way of war is to

fight wars very quickly and get them over and done with because they can't

sustain a long war. Well, you name the problem.

Hitler wasn't thinking in maritime terms.

He followed straight away a land -based strategy.

So, if you bring it to a nutshell, the Second World War was a maritime war.

The decisive battle fleet was the Atlantic. This was something that Hitler

understood fully.

Had Hitler prioritized the creation of a large U -boat fleet before the war,

there's every chance he'd have won.

There's a basic rule of supply and demand for any fighting fleet. Have one

of your vessels on combat patrol, one third traveling to or from patrol, and

third at base on training, maintenance and repair.

This meant that throughout all of 1940, there were never more than 14 U -boats

on patrol in the Atlantic at any one time.

And that was simply not enough to win the war.

One of the many triumphs of Nazi propaganda was to convince the world

Wolf Pact roamed the seas at will, but their limitations were soon to be

exposed.

These were not, in fact, submarines as we understand them now, but

essentially surface vessels with the capacity to die for a very limited

of time, a matter of a couple of hours before they had to come up for air.

As Allied anti -submarine technology swiftly improved, so losses of both

and men increased.

Admiral Dönitz was finding he just didn't have enough trained and

crews to replace them.

First thing that strikes me is there's a heck of a lot of wires and

dials and turning handles and so on. The training for this must be enormous.

Yes, it needs up to six months to train a U -boat crew because everyone on board

has to be fit with all these kind of handle and rules so they know what to do

just a case of emergency.

If you have only an expert in the diving process and he gets killed or injured,

you have a severe problem, especially when you're submerged.

So they took care that anyone on board knew how to handle the diving process.

The gruelling training and long voyages built a powerful esprit de corps among

the crew, from the newest recruit to the commander.

Just think about the men that are...

taking command of these U -boats by the middle stages of the war.

The average age of a crew member is about 20 years old.

Think of the awesome responsibility on their shoulders.

You're out at sea for up to weeks on end, on your own, and you are in

The decisions you make are literally...

a matter of life and death. No matter what you think about the Second World

and the part that Nazi Germany played in it, you cannot help but have an

enormous amount of respect for the young men that were commanding these U

-boats.

The Battle of the Atlantic exposed the limitations of the Type 7 U -boat.

There were simply not enough of them to destroy the Atlantic merchant convoys,

and the superiority of Allied air power and radar technology made them much

easier to detect.

The pilots have at their beck and call the swift and deadly destroyer escort,

packing a murderous wallop in her gun.

To make

matters

worse, by May 1943, Hitler was facing a new threat.

The victory in the Battle of the Atlantic meant that the Royal Navy could

from defence to attack along the extended coastline of Nazi -occupied

The German Navy had to come up with a new plan.

Trouble was, was how to deal with the mass of Allied shipping that was going

be crossing the Channel.

You know, it was going to be very crowded, very congested waters.

They didn't want lots of large -scale submarines. What they wanted was

that had comparatively small range.

but was small, very hard to detect, and which could maneuver very easily and get

close to enemy shipping and sink it. And this was the birth of the midget

submarine.

This 1945 American documentary takes up the story.

The development of the midget submarine by the Germans is another chapter in the

story of sneak craft attack.

The first to be developed was the one -man MOLK.

It was not very successful.

Its range was limited, and it was slow and cumbersome.

After two 15 -boat sorties, in which all craft were lost, she was abandoned.

Her successor was the streamlined beaver, which sacrificed strength for

The beaver, or beaver, had one pilot and was equipped with two torpedoes.

It was just seven metres in length and weighed three tonnes.

Powered by an Opel truck motor for service travel, it had a battery

electric motor when underwater.

Work on the first prototype began in February 1944 and was completed in less

than six weeks.

It then underwent a mere two weeks of testing before it was accepted into

service.

was still small enough to be launched and maintained at quickly constructed

strategic points.

These midget subs were soon to prove more dangerous to their crews than the

enemy.

To find out just what the thinking was behind these extraordinarily dangerous

machines, I'm going to the Technic Museum in Spreyer, just south of

I'm meeting up with a former submarine radio officer, Ulrich Zorn of the German

U -Boat Association.

I mean, I can only imagine what it must be like having to set sail in one of

these with a torpedo strapped to you. Alone.

Yes, I mean, that's horrendous. And anxious, I think. And how long would you

expected to stay in that?

Two days?

One day? Two days, three days, up to four days were the beavers too.

The beavers had many losses.

Did they? What was the percentage loss?

One says 69%, others say more than 70%, 75%.

And what were the problems?

Demonship, material damages.

Right.

So were they not particularly well constructed?

They were constructed at the end of the war.

So it's cheap.

And at the end of the war, they had less material.

They had problems with training for the crew. Right. So you're sending an under

-trained individual, one man, in a vessel, which frankly isn't as good as

might be. Yeah.

And so put that together.

For example, the engine in the Beaver was a normal petrol motor.

He has problems with explosives, and you have carbon monoxide, and lots of crews

died by carbon monoxide poisoning.

Oh, my God.

In 15 sorties using 163 Beavers, 53 of them,

almost a third, failed to return.

Weber was being used as a stopgap until the new midget sub, Seehund, was ready.

At just 12 metres long and weighing 15 tonnes, the Seehund was the largest of

the lot.

Equipped with a diesel engine and an electric motor, it was both fast and

to manoeuvre.

It carried two torpedoes flung either side of the hull.

and was the most successful of all the midget submarines, sinking some 90 ,000

tons of enemy shipping.

The Zeehund had a crew of two, a commanding officer and a leading

We're sitting in front of a Zeehund.

It's a pretty small submarine, and it's just horrendous conditions on it. You

could say horror conditions.

There were two men living in the boat. Right. A commanding officer.

and his engine officer.

He fired the torpedoes at command, and the fish slipped off the track on its

to the target.

They only had two wooden seats.

They had no heating inside the boat. The other problem was the meals.

They only had a small electric cooker.

Inside? Inside. They had no toilet in the boat, so they got special low

-fiber meals on the boat for 10 days maximum.

So you would stay up for 10 days. Yeah, they could stay up to 10 days. If they

had to do... Had to do their business. They put their feces into small tin

containers. And when they surf it, they threw it outside the boat. There was a

horrific smell in that boat. Yeah, yeah. They didn't get real sleep.

You can't sleep on that, can you? Because you've got to control the whole

the whole time.

Yeah, and so they got trucks.

During the war, it was fairly common practice for both the Allies and Nazi

Germany to use drugs to enhance the performance of their front -line troops.

Mainly, these were amphetamines and methamphetamines, although the Nazis

actually curtailed their use before the Allies did.

What's really strange, then, is that towards the end of the war, it is the

Kriegsmarine who are starting to reintroduce these drugs, and not just

methamphetamines, which, after all, is crystal meth.

but cocktails of methamphetamines with pure cocaine and other drugs beside.

And they were carrying out experiments with these drugs on prisoners at

Sachsenhausen concentration camp.

Then having done that, then issuing them to the crews of these midget

submarines. When you're talking about clutching at straws, I mean, these were

really desperate measures.

The last of these so -called submarines was probably the most dangerous of the

lot. A German human torpedo.

The operator enters the control torpedo, which is actually a standard 21 -inch

German torpedo minus the warhead.

This floating bomb had several variations.

The Negev and the Martin.

At its simplest, it was a one -man torpedo with the pilot sitting at the

in a plexiglass bubble.

The real torpedo, the child, was slung below the mother.

She carried it to within close firing range of the target.

But the pilot couldn't see underwater well enough to make an attack, so he had

to surface to get within firing range.

These vessels were to prove more terrifying for the pilot than for the

The first ones beached harmlessly.

They were the subject of more curiosity than alarm.

Later models of the Martin, like the one at the Technic Museum, replaced the

plexiglass bubble with a more substantial diving belt.

Here we are in front of a Martin. The Martin was called a one -man torpedo.

That's just mad, isn't it?

I mean, you can imagine, again, what you must be feeling like going off of that.

I mean, the controls you've got presumably are quite limited.

Yeah. You had only a small lever, like in a plane cockpit.

Right. The low silhouette of the craft running awash with only the dome visible

made the run -in on a dark night relatively easy.

But once he had fired his torpedo and his presence was known, he was quite

helpless against counterattack.

I don't understand it. Quite often the mechanism by which you detached yourself

from the torpedo didn't work. Yeah. So you ended up hurtling off with the

torpedo and effectively becoming a kamikaze bomber. Yeah.

Normally the pilot jumped out of the torpedo.

They had equipment like combat diver equipment, rubber suit, closed circuit

breathing system. Right, right, right. But you still had to be picked up,

Yeah, yeah. Hope getting picked up, for example, mine searching units.

Are most of these operations at night?

Yeah, yeah. So the chances of you being spotted and found on the sea at night?

Zero. Wow.

The losses sustained in these inhumane vessels were immense.

The average age of a Martin pilot was 19.

some 60 % of them were lost.

Another of Adolf's surprises, a human torpedo was driven ashore near Anzio.

His one -man crew, a 17 -year -old Kriegsmarine, a six -month veteran, is

and defiant.

But that didn't stop the Nazis training up the next generation of would -be

suicide submariners.

Well,

as a submariner yourself, you would never have wanted to be in one of these,

would you?

For me, that would be absolute horror.

That's not... Right.

Me going on a submarine, for me, that was a suicide command.

Yeah.

Richard's submarines were a desperate attempt to disrupt the cross -channel

invasion. But if they had any chance of winning the war, they needed to disrupt

the Atlantic sea lanes.

And for that, they needed something much bigger, much more revolutionary.

Something that could change the fate of the war.

With the war entering its final phase, It was clear the days of the Type 7 U

-boats as an effective fighting force were over.

The Nazi is forced to the surface.

Immediately a torrent of gunfire has turned on the triple sub.

It is doomed.

The terrible death toll and loss of vessels have made it nigh on impossible

Admiral Dernis to fight on.

This is the Laboue Naval Memorial.

Built in 1936 to remember those U -boat crews and sailors lost in World War I.

It's now been expanded to include all who died in both World Wars.

Inside, a mural is devoted to every vessel lost by the Kriegsmarine.

By the beginning of 1943, Admiral Durnett at last had the numbers of U

he'd wanted.

But his young and inexperienced crews were going to pay a terrible price

they were still using the same U -boats they'd been using at the beginning of

the war and simply hadn't kept pace at all with the technological advancements

of the Allies.

The hunters had become the hunted.

Only the introduction of a revolutionary new vessel could possibly give the

Kriegsmarine a chance to turn the tide in the war at sea.

They needed a submarine that could change the face of the war.

This is U -boat 2540, the Wilhelm Bauer, docked in the museum harbour in

Bremerhaven.

It's a Type 21.

And it's a vessel I've long wanted to see for myself.

It's the only surviving example of what, to my mind, was one of the most

brilliant military designs to have emerged during the Nazi era.

In order to try and understand the impact this machine was to have on the

of submarine warfare, I'm now on board with naval architect Alexey Konovalov.

I'm just really interested about what a leap forward the Type 21 was.

We are not talking about evolution anymore.

It's a revolution.

For the first time, the submarine was optimized for submerged operation rather

than for surfaced.

The Type 21 really was astonishing because it was the world's first proper

submarine.

So earlier models of submarine had actually been, strictly speaking,

submersibles. What that means is that, yes, they could operate under the

surface, but only for very limited periods of time, and also at much

speeds.

What really made the Type 21 stand out was, because of its revolutionary hull

design, greater numbers of batteries and the fuel it used, it could actually

operate faster.

under the surface than it could on the surface, and for much longer periods

underwater than early models like the Mark VII, the Type VII.

That really was massively revolutionary.

It was the first German vessel to be produced in modular form.

Construction began in 1943, with a total of 133 boats being completed as

assembly yards in Hamburg, Bremen and Danzig.

More than 250 feet long and displacing 1 ,620 tons, the Type 21

packed six torpedo tubes capable of firing more than 23 torpedoes.

It carried a crew of 57, could achieve a top speed of 17 knots submerged, and

survived underwater for up to 75 hours.

It was also the first U -boat to be fully streamlined.

All periscopes and radar masts were fully retractable, and even the flak

were built into streamlined turrets.

Its unique air -breathing snorkel enabled it to remain submerged to

batteries, something modern submarines still do to this day.

Well, up in the conning tower, this is absolutely amazing, isn't it? I mean,

dials and tubes.

Everywhere. I mean, when you're thinking about submarines, this is kind of what

you imagine, isn't it? But who would be up here and when?

This room is used by the commanding officer to lead the attack.

So he sits right behind you on the attack periscope.

Right. So I sit on here.

And I've got two pedals. So is this for controlling, turning it around? Yes. So

this can rotate? The whole turret can rotate.

And this presumably is where they've gone, but this is where the optics would

have been. So I'd be here controlling where I want to go, moving around.

It's just amazing.

Precision engineering, isn't it? It really is.

Actually, when looking at the level of mechanical engineering now in the 21st

century, the kind of precision is not much better than World War II.

We just put more electronics and intelligence in it. But then you look at

and you can sort of understand why.

We make our way down from the conning tower to the mess room, where we can

down on the huge complement of batteries that gave the Type 21 its immense

power.

So these are batteries.

This is half of the battery capacity this submarine actually has.

Really? They increased the amount of batteries times three, and the power.

of electric drive times 10.

Right. I mean, they do look like giant car batteries, don't they? Yeah, because

this is the same principle. They are more sophisticated because they have

additional system for acid circulation and so on, like every modern submarine.

So, presumably, the faster you go, the more revolutions you need, the more

you're using, the quicker they use up their energy.

Yes, exactly.

For this reason, until today, every submarine without air -independent

propulsion has very low endurance when running at high speed.

They can run for many hours at 3, 4, 5 knots.

Right. But if they have to go for 70 knots, it's just about for a couple of

hours.

This is the only footage I've been able to find of the Type 21SC.

U -boat 2513 was surrendered to the Americans, and this is taken as they

evaluating its design and performance.

It was information that was to prove invaluable to the future of submarine

design.

I just find it absolutely stunning that in the era of the Second World War

you're creating something as sophisticated as this. I mean, you look

someone has to invent this, someone has to design this, and teams of engineers

have to create it. It's a very complex thing, isn't it?

Yes, and without modern computer -aided design technology, it's just some

guy standing and drawing something.

I couldn't imagine just doing this for months and years without a computer.

Yep.

I really do think this Type 21 is absolutely amazing.

And, you know, I just can't help thinking that the Nazi regime had a

opportunity with this that they just didn't exploit at all.

You know, they don't start this until 1943, and yet they've got the

the know -how, much earlier than that, and they just don't do anything about

It's just this really bizarre prioritisation.

You know, just imagine if these had been around in the early part of the war.

The only way to really dent the Allies is by destroying their shipping.

This. is the weapon that could have done that.

And yet, incredibly, only two ever go on war patrol right at the very end of the

war. It's a massive opportunity miss for the Nazi regime, and thank goodness for

that.

This particular U -boat never saw combat service and was scuttled by its crew in

1945.

And as I'm about to find out, it was lucky to be built at all.

As the Second World War moved towards its endgame, the Nazis made one more

desperate roll of the dice.

On the 18th of February, 1943, Joseph Goebbels announced a new phase for the

Germans, that of total war.

The entire country was to be mobilized in its defense.

An armaments production was to be increased threefold.

Rapid construction of the Type 21 U -boat was seen as vital to this

but Nazi Germany's meagre resources were becoming ever more stretched by the

Allied bombing campaign.

Most of their shipyards now lay in ruins, so a very special, very secret

assembly facility needed to be built that was immune to Allied attack.

One with walls and a roof so thick,

No bomb would be able to smash it.

It's early 1943, and the Nazi high command urgently needs to get the Type

-boat in the water.

The Valentin assembly plant is to be their answer.

Built of reinforced concrete, It would be the largest fortified U -boat

in Germany, at 426 metres long and 27 metres high.

The walls alone were to be four and a half metres thick, the ceiling an

extraordinary seven metres at its thickest.

The engineers were given just 22 months to build it, and it was built largely by

slave labour.

For the past ten years, museum curator Dr. Markus Meyer has been refurbishing

the rundown factory as an example of German engineering construction, but

as a symbol of the horrors of war.

So how many people are involved in constructing something quite as enormous

this? We're talking about...

8 ,000 slave workers a day plus 2 ,000 engineers, German workers and guards.

And who were these workers?

They were slave workers from all over Europe. They were concentration camp

inmates. Yes. And they were inmates of a local police camp.

And presumably conditions were not good. No, they were very, very bad.

One of the biggest problems was to get enough food.

Most prisoners had a weight of about 46 kilograms after a short period of time.

That's just nothing.

There was basically just soup.

Cabbage soup with cabbage as an idea of cabbage.

So not enough calories to stay alive just by doing nothing. And they had to

very, very, very heavy work.

Carrying stacks of cement, metals, everything.

The living conditions were quite bad.

And do we have any idea how many people died as a result of building this? We

cannot say the exact number, but about 1 ,300 are proved.

Of the 10 ,000 to 12 ,000 men who worked on the construction, it's now estimated

that as many as half perished in the process.

From the perspective of today, this looks like an act of gargantuan folly.

It was dreamed up by Dönitz, by then a grand admiral, in collaboration with

Hitler's favourite architect, Albert Speer.

In the aftermath of the war, both these men honed a carefully cultivated image

of being good Nazis, not really supportive of the worst of the regime.

It's an image that looks more than a little shaky in the shadow of the

bunker.

Why are they doing this?

Dernis knows that the U -boat war is over. I mean, really? Is a Type 21 going

come in to make a difference? I mean, can he possibly believe that? It's hard

say if he really believed it. I think, in a way, he did. But it's kind of

delusional at that point.

But the thing is, total war means not achieving a kind of rational goal

in a war, getting resources, getting territory.

Total war means we are in the end fight and there's just one survivor. Yeah.

There's no chance. It's all or nothing. All or nothing. So if you have the

technology to build a Type 21, which is potentially a game changer, it's worth

going and building a 400 meter long bunker. Exactly. Yeah.

By any cost.

Right. Money.

Yeah, and if it costs 6 ,000 lives in the construction, nobody cares. This is

really one of the last straws they had.

And it's madness.

Yeah, yeah. And that's the special thing about this bunker.

Inside, it's completely logical.

Right. But outside, it's madness.

The madness lay not just in the construction.

but in the belief that a building this size could be kept secret.

I was off to photograph Hamburg.

Unbeknown to the masterminds behind the Valentin, the Allies had been watching

its construction from the very start.

Coming in over the target, I started the automatic camera.

Marcus has uncovered some old files in the British National Archives, which

an insight into the quality of their surveillance.

What the British get out of their air surveillance...

documented um first note is from i think may 43 right uh

okay there's something going on let's check it out and after that we have

reports every three to five months getting much more precise every day

right um even drawings of the bunker okay just taken by by exploring

the photographs they took Right. And their special interest was the thickness

the roof. Right.

They were waiting for the building to be well into construction, but not so

complete they would be unable to penetrate it.

From the reconnaissance photos, the Allies correctly worked out that one

the roof was only five metres thick, not seven.

On the 27th of March 1945...

617 Squadron, the Dam Busters, struck with bombs known as Grand Slams.

These 10 -tonne high -explosive earthquake bombs couldn't penetrate 7

concrete, but they could break through 5.

And that was the part that was successfully targeted.

Well, Marcus, that's a pretty big hole in the roof there. Is that the fatal

blow? That's one of the two fire blows, yes.

Yeah, wow.

And it was caused by a 10 or 12 ton bomb.

Yeah, a grand slam. A grand slam.

Yeah, and this looks very much like the remains of one of the grand slams that

was dropped.

It's amazing, isn't it, that after all those months of construction, just a

couple of bombs, and that brings the whole thing crashing down to a halt.

Yeah, all the planning that went into this place were basically useless,

this was...

Highly visible.

I mean, how could it be anything but?

Yeah, you couldn't camouflage it. No. This bunker could have been built only

because the Allies let it happen.

They could have destroyed it from day one. They didn't because so many

were used here without any danger to anyone. At that point where they

okay, the Germans will finish the roof finally up to seven meters.

They just flew this one attack.

Right. One.

And two bombs hit, and this whole project was gone.

You know, on one level, this place is just so impressive. To think that this

built, you know, in the second half of the Second World War, on such an

scale, is just incredible.

But on another level, this is just absolutely insane.

I mean, you know, Germany is losing the war. Yes, they've got the Type 21, but

they simply cannot build enough of them. And this is not going to be the answer,

because let's just say they do manage to complete the construction of this, and

it isn't actually bombed.

The final assembly of the U -boats, the Type 21, is going to be here.

This would have been a dry dock. You fill it up with water, and then you sail

out. But you sail it out into the River Visa, and that isn't deep enough to

submerge one of these submarines.

So they would have to sail all the way down the river, quite a long way to the

North Sea, above the waterline.

And there is just no way, by that stage of the war, that the RAF or American

planes are not going to be able to spot that.

and destroy them en route. It's just inconceivable.

And to imagine any other course was just so illogical, so irrational.

And it just underlines, I think, just how crazed the senior leadership

in Nazi Germany had become. I mean, what were they thinking?

The war was over.

The U -boat fleet was destroyed, with an appalling loss of life.

At the start of the war, the U -boat arm had been just 3 ,000 men strong.

By the war's end, ten times that number, more than 30 ,000 had been killed.

Had Hitler been a halfway competent military strategist, and had Dönitz got

way in 1939, the war might have ended very differently.

I think what's so amazing about the U -boat arm is you can see the potential

there. You can see how a properly equipped modern U -boat arm could have

wreaked havoc with the Allies.

But it's too little, too late, and not enough focus.

Well, it's the problem if you try to fight the world.

with a handful of ships.

Yes, exactly.

It was the right strategy to follow, but with very limited means.

And from a mere military point of view, that was the key problem.

They had great successes, but in the end, they simply ran out of breath.

While Dönitz failed in his attempt to sever the vital Allied supply lines

the Atlantic, no one can doubt the achievements and sacrifices of the U

arm, nor the astonishing developments in technology that it inspired.

You are aboard one of the newest attack submarines in the US Navy.

It had a fundamental influence on post -war submarine development in both

America and the Soviet Union.

In the years since World War II...

The rapid development of underwater technologies has thrust the submarine

the forefront of the naval balance of power.

Such was the legacy of the Type 21.

Submarines today are faster, better equipped, and have longer endurance than

ever before.

It demonstrated the Nazis' faith in the power of technology.

Perhaps given more time, it could have even helped them win the war.