Original subtitles

- Bull's eye.

- Achtung! Achtung!

- Dive! Dive!

- Why the hell have you dived?

(clatter)

NARRATOR: Britain may have dealt with Donitz' aces...

- No way back to Germany this time.

NARRATOR: ..but his U-boats keep coming.

- Fire.

- New orders for Group Paukenschlag.

- Attack at will in all coastal areas.

NARRATOR: They sink ships faster than Britain can build them.

- If we keep losing ships at this rate,

the country will be down to just a few weeks of supplies.

- People will be starving to death.

- Happy hunting.

NARRATOR: The Royal Navy turned to retired war gamer,

Commander Gilbert Roberts...

...and a group of young women.

- Sir.

- Ladies, if we lose the battle of the Atlantic, we lose the war.

Our job is to find a way to sink the U-boats.

That is what we will do here.

- Sir, the board is set.

- By recreating battles and playing through scenarios,

in a war game.

- Is that Donitz' master tactic?

- We need to work out how to destroy them.

NARRATOR: Gilbert Roberts reports to Western Approaches' command,

the Royal Navy's Centre of Operations

for North Atlantic convoys, in Liverpool, England.

- Gilbert Roberts could be doing so much more at this point.

- Here's a man who's had two years training in war games.

War gaming allows you to understand how tactics work

and it allows you to explore new tactics.

- Churchill couldn't be less pleased with how the battle is turning out.

The fact that they're losing hundreds of thousands of tons

of merchant shipping to U-boats.

- Enter.

- Churchill has to not just stay in the war, but win it,

and you can only win it if you win the battle of the Atlantic.

- Sir. Commander Roberts.

- Thank you, that will be all.

Commander Roberts retired.

I thought London was sending me a Captain?

- No, sir, Sector Commander:

Portsmouth Naval Anti-Invasion Battalion.

The Home Guard?

Instructions from the Admiral say I'm to...

give you the top floor of the exchange building. For?

- A school, sir. - School?

- A tactical school.

The Prime Minister has asked me to analyse U-boat attacks,

decipher their tactics and develop counter tactics to sink them.

These would then be taught to Escort Commanders at the school.

- We already have a counter tactic, Roberts.

Buttercup, developed by our own Commander Walker,

a man who has actually sunk U-boats.

Have you? - No, sir.

And I'd very much like to begin with Buttercup.

By analysing Commander Walker's actions,

I can then play through other scenarios in a war game

and identify any tactical weakness that we -

- War game? Tactical weakness?

I'm sorry, but what does a Sector Commander of the Home Guard

know of tactics?

- I spent two years at the Portsmouth Tactical School, sir.

War gaming... (coughs)...

...before retirement.

- A school to play games.

- And I need men to staff the Unit too, men with good analytical minds.

good with records, but mostly good at playing the game.

- Commander, I'm in the middle of fighting a war.

All my best men are at sea.

Might be able to find a couple of our unfit for active service,

but if you need more to play your game, you should speak to London.

- Thank you, sir.

- Oh, and Roberts, this school.

perhaps you can run occasional courses

for half a dozen reserve officers,

but don't bother me with it. I'm a busy man.

Dismissed.

- Percy Noble isn't taking on board the importance

of finding new tactical ways forward.

- (coughs)

- Donitz is a tactical master.

This is a time where it's more crucial than ever

that he listens to Roberts.

- Sir. Secrecy is paramount.

- Yes, quite right.

NARRATOR: And for the Royal Navy,

help arises from an American tragedy.

After the attack on Pearl Harbour, the USA declares war on Japan.

Four days later, Germany sides with their Japanese ally

and declares war on the USA.

The Americans have already been unofficially supporting Britain

through the war.

Now they mobilise at full strength.

- The idea was to get to Germany to defeat it first,

but of course doing that meant getting supplies and equipment

and now manpower as well to the British Isles

in preparation for an eventual invasion of Nazi Germany.

But the American involvement created new opportunities

for the German U-boats to attack American shipping.

Donitz saw this immediately.

- The United States Navy should have been prepared

for a submarine campaign,

but the problem they have in early '42 is,

they have too few destroyers to protect merchant shipping.

Most of them had gone to the Pacific to fight the Japanese.

NARRATOR: This lack of protection

presents Donitz with a golden opportunity.

e measures his U-boat captain's success

by the number of ships they send to the bottom.

- Admiral. Orders for Group Paukenschlag.

Proceed to Naval square C-A-28, New York.

- Yes, Herr Admiral.

- They knew the shipping would concentrate off New York,

off Cape Hatteras; off Cape Cod.

- American involvement in the war gave the U-boats

a lot of new targets off the American coast.

- Herr Admiral?

- Have the Americans learned nothing from the British?

Very heavy traffic. Mainly north-south.

Very many tankers, Occasional neutrals.

- No surveillance. - (chuckles)

- They're not even trying to protect their ships.

- The United States Navy don't have escort vessels they need

to establish a system of convoy, so they decide not to do that.

There's a marvellous directive from the Office of War Information.

Quite simply, "The Germans can sink as many ships as they like,

really doesn't matter. Because American industry

is just gonna bury them in new shipping."

- All the more prey for the wolves to feed on.

New orders for Group Paukenschlag.

Attack at will in all coastal areas.

- January of 1942. They sank 41 ships, 250,000 tons

in just two weeks.

A lot of those sinkings were just off the coast of the United States,

literally within sight of American home territories.

- German success is so profound. it's known as the second happy time

for the U-boat fleet.

- With the Americans being destroyed in such numbers,

it's more and more important that the convoys that do survive

are protected, that the Royal Navy gets the ships across.

NARRATOR: The scale of the task is enormous.

Every available man is put to work. But there aren't enough.

- Without women, we realise we can't win the war.

That is a whole new ball game for men to get their heads around

and for young women to engage with.

NARRATOR: The Royal Navy are forced to rely more and more

on Vera Laughton Mathews' Wrens.

- I do appreciate having your Wrens here.

it's certainly brightened the place up.

- They can do more than that.

Much more.

- To begin with, the Wrens have just nine roles,

and they are fairly humdrum.

If you're lucky, you're a typist. Or a driver.

Those minimal opportunities expand to over 125 roles.

NARRATOR: One of those are as codebreakers

at the highly secretive Bletchley Park,

deciphering radio messages between Donitz and his U-boats,

providing vital intelligence on when to expect U-boat attacks.

But despite the best efforts of the men and women of the Royal Navy,

they still haven't deciphered the enemy's tactics.

- Even though Roberts initially gets a very frosty reception,

he is delighted to be back.

He'd been cast out of the Navy due to having TB four years earlier.

- (coughing)

- This was a man who had spent a lot of time in the inter-war period

thinking about these problems.

He can use his skills, he can contribute to Naval success

and if possible, he can contribute to victory.

- As if to undermine Roberts' position even further,

he isn't put in the main headquarters.

His offices are in a building which hasn't even been finished.

It's still under construction AND it's been bombed!

- What's this? (clatter)

- A gift from Hermann Goring. Damage from an incendiary bomb.

- Needs to go. Arrange for it to be cleared.

- Yes, sir.

- (coughs and wheezes)

I'll need battle reports.

Anything detailing a successful U-boat kill,

including convoy HG76.

Commander Walker's Buttercup triumph.

- Yes, sir.

- He needs as much information as he can get

about what's really facing commanders

when they're out in combat,

to figure out what the U-boats are doing and how to defeat them.

- I'll also need supplies to build the game board.

- Canvas sheet,; roll of linoleum...

- Chalk, string, paint

and model ships, yes?

- Yes, sir. - Very good.

- These requests raise eyebrows at Western Approaches.

Here is this newcomer who wants to play games

while battle rages in the Atlantic.

- Anyway, sir, all this tactics and war gaming might be for nought.

We captured that Otto Kretschmer

and they already started interrogating him.

Surely he'll spill the beans and give up all of Donitz' secrets.

- Surely.

NARRATOR: From 1939 to 1941,

Kretschmer unleashed a reign of terror against Allied shipping.

- A hunter's moon. Just as I like it.

Prepare for attack. - Yes, sir.

- Fire bow torpedo.

NARRATOR: Sinking 47 ships across the North Atlantic,

over 273,000 tons,

more than any other U-boat ace.

- That's as good as it gets.

NARRATOR: The human toll is 830 lives.

For his service to the Third Reich,

Hitler awarded him the Knight's Cross of the Iron Cross,

with Oak leaves and swords.

- Danke schoen.

NARRATOR: At the time, Nazi Germany's highest Naval award.

- Achtung! Achtung!

Dive! Dive!

- Why the hell have you dived?

Are you sure we couldn't have got away on the surface?

NARRATOR: But in March 1941, his luck ran out...

- Sir, we lost both thrust from the propellers.

- Blow the ballast tanks, everything we've got. We have to lose depth.

Prepare scuttling charges and destroy all documents and ciphers.

No way back to Germany this time.

- Otto Kretschmer is this extraordinary U-boat ace.

He's caught alive. That is such a win for the Allies.

The MI9 have got hold of him.

MI9 is a unit established to interrogate prisoners of war.

It's like a latter-day Guantanamo Bay.

Here's your chance, boys. Drill into him!

Download his microchip of knowledge

and you are gonna turn the tide of this war.

- No, thanks. - You speak English.

Would you rather we spoke German? - No. English is good.

I might as well get used to it now

- Quite an impressive tonnage, Commander Kretschmer.

Must make you very popular back home. The Tonnage King!

Isn't that what Goebbels calls you?

- It's just propaganda. I'm a good copy for the Nazi papers.

My picture gets more women waving flags,

more men signing up to the U-boat core.

What for? To sink more ships?

For Hitler?

Sorry if I don't seem too enthusiastic.

I grew weary of this war long ago.

- You won't miss sinking ships?

- I have sunk enough ships.

The thrill of the hunt left me long ago too.

- And how do you..."hunt"?

You've sunk more ships than anyone.

How do you do it? What are your tactics?

- A U-boat captain, I mean a real captain,

has to be able to take advantage of whatever the passing moment offers.

You never know when you'll stumble upon a convoy.

A real captain is born with the intuition

to know when to attack

and how to press home your advantage.

- Smashing.

- Do they get the key to Otto Kretschmer's knowledge?

Do they find a way in? Do they hell as like!

This guy ain't the top U-boat captain for no good reason.

NARRATOR: Kretschmer reveals very little to his captors.

Donitz' U-boat tactics remain a mystery.

NARRATOR: At Western Approaches' command,

Roberts tried to decipher them.

- Sir, the report you requested. - Ah...

Convoy HG76.

Commander Walker's famous Buttercup tactic.

- Thank you. - Sir.

- A Report of Proceedings was a standard report

that was written by anybody in the Navy

who had encountered the enemy.

It explains what the enemy has done,

but it also explains what the commander from the Allies has done.

- Buttercup astern!

- H276 is important because Walker had some success during it.

He wants to understand why Walker was successful.

(chink of glasses) - Sir.

- What has he thought up?

Why did he behave the way he did?

But if you're looking at a report, any kind of report,

they're very, very dry.

They don't really tell you anything about the human side of decisions.

(knock on door)

- Enter.

Sir. Commander Roberts.

- What is it, Roberts?

Sir, I'd like permission to speak with Commander Walker,

about convoy HG76.

- Don't you have his Report of Proceedings?

- Yes, sir, I do.

- And you've read it? - Yes, sir.

But to truly understand how Buttercup works,

I need to speak with the Commander.

What assumptions did he make?

Why deploy his escorts when he did?

- Roberts, Buttercup works. I's a sound tactic,

which is why I ordered it to be put into group operational instructions.

- I'm aware, sir.

- Now our escorts are being fitted with a new piece of technology.

Ship-mounted radar.

We'll be able to spot U-boats on the surface miles away.

- That would be a great help, sir, undoubtedly.

But to complete my work, I will still need to see Commander Walker.

- (huffs) Very well.

When Walker gets back from sea, if he can spare the time, you may.

- Thank you, sir.

- Now, if you don't mind...

NARRATOR: And Noble has another reason to be confident.

The work of the Wrens is turning Western Approaches' command

into an intelligence hub.

Up and down the country,

Wrens working in radio listening sites known as Y-stations

are tracking U-boat positions.

- My first station was on the Yorkshire coast,

not very far from Scarborough,

where there was a very big listening centre.

NARRATOR: By comparing the bearing of the U-boat's radio signal

with another Y-station, the U-boat's position can be triangulated.

- U-boats of course very seldom spoke,

but now and then one would come up

and would do a signal to its base or to other U-boats.

When they did, it was a very, very tense atmosphere

because they were such a menace to our convoys and ships.

I was there when a U-boat came up

while they got the signal from the U-boat down

and particularly the position of the U-boat,

because they could then report this back to Admiralty

and they might be able to take action.

- Very good.

- That intelligence arrives pretty pronto, via radio,

to Western Approaches, telling you the real-time positions

of U-boat flotillas, so you plot them, you mark them

on your giant map on the wall.

NARRATOR: And Western Approaches are also benefiting

from long-range aerial photo reconnaissance.

- A lot of the analysis of these photographs was done by women.

They wanted to see for example the U-boat pens along the French coast.

By looking at these sorts of images,

you had more of an idea of when they were going to leave the pens,

when did they get back, how long were they out at sea,

and what was their direction.

NARRATOR: It means Western Approaches are much more aware

of when to expect attacks.

- Excellent, thank you. That's good work.

NARRATOR: But they still can't work out

how the U-boats are attacking the convoys.

- Sir, this is the room.

Candidates will be with you shortly. - Thank you.

- Before he could begin his work, Roberts clearly needs a team.

- He needs people who are "whip sharp".

He needs the finest brains, boys who are gonna knock the tactics

back at the enemy.

- Please, take a seat.

- Lieutenant Commander Cousins, DSC, sir.

- DSC? - Distinguished Service Cross, sir.

Awarded for gallantry against the enemy.

- I see. What experience do you have of tactics?

- Tactics?

We smash the U-boats with depth charges. That's all we need.

We hound them out of the Atlantic.

- I see.

Thank you.

- Thank you.

(knock on door)

(door opens)

- Lieutenant Commander Higham, sir.

- Your experience of tactics?

- Sir, I've served on both submarines and ships.

- And tactics? - My ship sunk.

I had to be hauled out of the water on a rope! (chortles)

- Dismissed.

- Donitz is a genius. He needs men who can think mathematically,

tactically; very clear-headed, clear-minded.

These are clearly not the sort of men he's going to need

to decipher Donitz' tactics.

(door opens)

- Commander Roberts. Vera Laughton Mathews,

Director of the Women's Royal Naval Service.

- The Wrens?

- I hear you're in need of staff.

- I can meet all your requirements.

I've been recruiting the people you need for three years.

- Wrens? I need Naval Officers!

- And how's that working for you, hm?

Wren Drake, please enter.

Please take a seat.

...Elizabeth Drake, the daughter of an insurance actuary, yes?

- Yes. ma'am.

- Measuring risk must run in your family, yes?

- Yes, ma'am.

- Thank you, Drake. That'll be all. - Yes, ma'am.

- Sounds essential for your tactical game, Commander.

Next!

- Wren Nancy Wales, sir.

- Wren Wales, what experience do you have of tactics?

- Well, sir, I captained the Yorkshire hockey team for years.

- An expert in team tactics. Thank you, Wales.

Janet Okell. I hear you're a formidable bridge player.

- Well, yes, ma'am.

- And what makes for a formidable bridge player?

- Well, reading your opponent is important, ma'am.

- Reading opponents. And scenarios strategically?

- Ma'am, what is this all about?

- Thank you, Okell. That'll be all.

And finally, a real gem.

(knock on door) - Wren Laidlaw, please enter.

- Good afternoon, ma'am. Sir.

- Wren Jean Laidlaw. Accountant. - Yes, sir.

- I haven't met a woman accountant.

- I'm one of the first to qualify in the United Kingdom, sir.

- I see... A keen mind for numbers, I suppose?

- Yes, sir, very keen.

- Just what your game needs

to calculate those moves.

I suppose.

- Indeed.

- Thank you, Laidlaw. That'll be all.

- Yes, ma'am. Sir.

- Bright.

- All of them, Commander.

And they all bring a special set of skills to the table.

- Exactly what the game needs.

- In the early war period, almost every nation does not consider women

for these sort of roles.

The Wrens were a risk.

- The task these young women are set

is one of the most important in the war.

If the battle of the Atlantic is lost, Britain is lost,

and if Britain is lost, the Western Allies will probably lose the war.

NARRATOR: In Liverpool, Gilbert Roberts and the Wrens

begin the next phase of their mission.

- What knot is that?

- It's a bowline, sir.

- Where'd you learn it? - The Sea Rangers.

- The simplest and most resilient.

Very good.

Men, rig the canvas sheets around the frames like these.

- Yes, sir. Sir, your linoleum, string, paint, chalk

and model wooden ships.

- Excellent.

Any news of the great Otto Kretschmer's interrogation?

Did he spill all their U-boat secrets?

Of course he didn't. That would be far too easy.

It's up to us to decode them,

and the first step for that is to build the board for the war game.

- The board, sir? - The board.

(coughs) The board.

- Sir, are you all right?

- The board.

- This is the thing which is going to win the battle of the Atlantic.

The idea is preposterous.

- And sir, Commander Walker's just returned from sea.

He's waiting in your office.

- (angry) Well, why didn't you say?

Buttercup.

Wren Laidlaw? - Yes, sir.

- Wait ten minutes, then join me with Commander Walker.

- Yes, sir.

- Roberts wants to understand how Buttercup works.

- Commander Walker.

- The chance to sit down with Walker

and actually try and get inside his mind...

This is a crucial moment.

- What's this about, Roberts?

You want a debriefing on Buttercup to help play a game?

- A war game, to play through scenarios,

decipher Donitz' tactics and learn how to sink his U-boats.

- (scoffs) Something I've actually done, using Buttercup.

- Which is why I wanted to speak with you.

Convoy HG76.

32 merchant ships sailing homeward from Gibraltar.

19th of December. HMS Stanley is torpedoed and you order Buttercup:

What happens then?

- Buttercup astern!

Well, I've... I've drilled all my Escort Commanders

to go to battle stations on the order Buttercup.

They turn away from the con...

- Ah, Laidlaw. Please, take a seat.

Commander Walker, this is Wren Laidlaw, member of my staff.

Laidlaw is a, is an accountant by trade.

- I've never met a woman accountant.

- Laidlaw is one of the first in the country to qualify,

so now you have.

- Uh, the Stanley was hit.

We can't be sure exactly where the U-boat fired from.

They fired from outside the convoy in.

Once a ship is hit, they escape by motoring along the surface.

On the order Buttercup, all escort ships turn outward

away from the convoy, full speed,

chase down the fleeing sub.

- Sir, how can you see the U-boats?

The attack was at night, wasn't it?

- We fire star shells. Flares that light up the sea.

We search for 20 minutes, we spot a U-boat,

uh, well, we destroy them.

Just find that damned hearse and sink it.

Buttercup, starboard.

Come into our little trap.

Prepare to ram.

Buttercup has prevailed.

Dearest Buttercup.

- And it works?

- My dear, we only lost two convoy ships.

I personally sank two U-boats

and three more were hit by other forces under my command.

- Sir, HG76 had 16 escort ships

protecting 32 merchant vessels.

Is that a heavy escort?

- Uh, well, more than most North Atlantic convoys,

but sailing out of Gibraltar, if you don't go in heavy,

then you're asking for trouble.

- And how many escort ships were lost?

- Two escorts.

- Including the aircraft carrier HMS Audacity?

Buttercup works.

We sank five U-boats.

Admiral Noble even asked me to write it up

for the Escort Group Operational Instructions.

- Yes. So I understand.

Thank you.

- Everything they tried previously just failed.

So this was really the first glimmer of success.

It WAS a success.

Walker manages to sink two U-boats himself and three others were sunk

in this whole operation, but it was very, very costly.

- Everything's in place. Roberts has got his game.

He's got his bits in order to make his game work.

He's got detailed battle plans so he can work out

what the U-boats have been doing.

To help him, he's got his team of brilliant minds,

these young, dependable women from all sorts of backgrounds.

- So smart!

- Vera Laughton Mathews must be incredibly proud.

She's hand-picked these young women herself

and these women are not being asked to do menial tasks

of answering phones or driving cars.

- This was taking the fight to the enemy

and spearheading a mission to save lives at sea.

This was using grey matter, women's grey matter.

- Wrens, let's make a start.

Welcome to the Western Approaches Tactical Unit.

WATU for short. (door opens)

- Commander Roberts? (door bangs shut)

Janet Okell. Sir, I'm so sorry I'm late.

I took a wrong turn, and then another, and another

and I couldn't find my way back. - It's all right, Okell.

- So sorry, sir.

And I don't have a uniform yet.

- That's fine; I'm glad you could join us.

The uniforms are here. Please, collect yours.

This is Chief Yeoman Rayner.

He worked with me at Portsmouth.

He knows the game inside out. - Sir, this isn't a Wren's uniform.

- You'll be working a lot on the floor.

- Sir?

- Measuring on your hands and knees. - Sir.

- For this work, the standard skirt isn't exactly appropriate.

- WE'RE wearing the trousers now!

- (all chuckle) - Indeed.

Ladies, if we lose the battle of the Atlantic, we lose the war.

Our job is to find a way to sink the U-boats.

But before we can do this, we need to decipher Donitz' tactics.

That is what we will do here, by playing through scenarios

and recreating battles... in a war game.

This is our board.

The block for the convoy.

Model ships for the escorts.

The players are divided into U- boat captains

and escort commanders.

The escort commanders stand behind these screens

and view the board through these lenses.

Wren Drake, would you...?

How much of the board can you see?

- Sir, I can't see anything.

- Ah, yes. Bit of a problem.

How about now? What can you see?

- Not much. Just a few models.

- Just like at sea. - Exactly.

It mimics limited visibility. Just like a convoy,

stretched for miles across the ocean.

- And the U-boat Captain, Commander Roberts?

- The U-boat Captain sits at the high table.

- There isn't a model for the U-boat.

- No. The escorts can't see the U-boats, just like at sea.

- So how do we plot their positions, air?

- Brown chalk.

Drake, can you see the U-boat track? - Not a thing, sir.

- Brown on brown. Thank you, Drake.

An adjudicator hands action events to the players,

written on these chits.

U-boat contacts, aircraft sightings, ASDIC pings, ships torpedoed.

The players are then given two minutes to make their move.

They write down their instructions on these movement chits -

course, speed,

ASDIC sweeps, depth charges dropped.

They return them in silence so the opposition doesn't know their plan

and the plotters move the models.

The aim of the game is to sink the U-boats.

And the battle report we'll start with...

is convoy HG76. Buttercup.

NARRATOR: Despite the Royal Navy's confidence

that ship-mounted radar and better intelligence

will turn the tide against the U-boats,

they're still sinking ships faster than Britain can build them.

More and more U-boats keep coming.

- Donitz developed the idea that 100 U-boats

on active patrol in the North Atlantic

could all but shut down trans-Atlantic shipping.

NARRATOR: In April 1941,

Donitz had only 28 U-boats hunting at any one time.

By the beginning of 1942, that number has exploded.

- How many boats do we have at sea?

- 88, Herr Admiral. - 88?

That's close to the 100 we need to shut down the Atlantic.

What is the monthly tally from Group Paukenschlag?

- Paukenschlag?

- A five U-boat wolf pack.

23 merchant ships sunk

for 150,000 tons in the last month,

and they ran out of torpedoes.

- But they are just five U-boats.

This is a feeding frenzy.

They are gorging themselves off the coast of America.

- Fire!

- The German U-boat crews are having a field day

off the American East coast. There were so many available targets

that U-boat skippers could pick out the most useful ones.

- This led to a kind of specialisation on hunting tankers,

the most valuable prizes,

because fuel meant war.

- Britain's war machine runs on oil

and very little oil is making it across the Atlantic.

Without fuel, Britain dies. The war effort stops.

This is a very productive hunting ground.

Let's go for the jugular.

- With everything in place, Roberts and his team begin.

The first thing they're gonna do is look at Buttercup

and the HG76 convoy engagement.

- The first time that they actually set up for the war games,

they don't play a game itself:

This exercise is really for Roberts to get all of the ducks in a row;

all the pieces on the board, to figure out what happened.

Every single thing they know, step by step.

Where did the convoy go? Where were the escorts?

Where were the U-boats sunk?

- It provides Roberts and his team with a bird's eye view.

That is gonna give them a real advantage in understanding

what went right on the side of the Royal Lena,

but also what the German U-boats themselves are most likely doing.

- Sir, the board is set.

- Excellent.

Let's begin.

- Convoy HG76. 32 merchant ships with an escort screen of 16 ships.

- The escorts form a protective perimeter.

A merchant ship is hit. What position?

- The merchant ship, sir? Not the escort, HMS Stanley?

- No, the merchant ships are our lifeblood.

I want to see how they're targeted.

- The SS Annavore, convoy position five-three.

- Fifth column, third ship.

- Now what? - Commander Walker orders Buttercup,

The escorts turn outwards at full speed

and fire star shells to illuminate the sky.

- They speed AWAY from the convoy, to try to spot the U-boat.

- Walker manages to sink a U-boat earlier at the rear of the convoy.

- The stern of the convoy. - Astern.

- Good. At Least one U-boat down.

Proof they attack from outside the convoy,

like Commander Walker said.

Is something wrong?

- A merchant ship was hit in the centre.

Can they even hit...

What's the range of a torpedo?

- Uh...

- Leave the board as is. I need to make a phone call.

- Operator? - Flag office, Submarines, London.

- I'm connecting you now.

- Roberts has an old friend who's based at Submarine Command.

So he puts in a call. To his surprise,

it's answered by the Commander, Submarines for the Royal Navy,

That's Sir Max Horton. (telephone rings)

- Admiral Horton?

- Apologies, sir. I was hoping to speak with your Chief of Staff.

- Captain McIntyre isn't present.

You're through to the Flag Officer himself. Who is this?

- Max Morton is a big

He is the head of the Royal Navy Submarine Arm.

He was a submariner in World War One.

He knows everything there is to know about submarine warfare.

- Sir; it-it's Commander Roberts

of the Western Approaches Tactical Unit.

I wanted to speak with Captain McIntyre on submarine tactics.

- I served in subs during the first war. What do you need?

- Oh, thank you, sir.

What is the range of a German torpedo?

- A G7E? Roughly 5,400 yards, but that's the limit.

Effective rang, expect to halve that.

- Now, remember, the ship that was sunk in HG76,

that ship was in the middle of a convoy.

A convoy is 10,000 yards across, How does that make sense?

- Commander, are you still there?

- Yes, sir.

One more thing, if I may.

During the first war, would you ever fire from inside the convoy?

- Of course. It's the only way of being accurate.

- They're inside...

- They're bloody well inside.

- Roberts, does this answer your question?

- Yes, sir. More than you can know.

Commander Walker, the Royal Navy,

they believe the U-boats fire from outside the convoy.

But what if they're wrong?

What if they're firing from INSIDE?

- The U-boats Walker sank.

- It would mean Buttercup is based on a false assumption.

The Royal Navy are relying on luck to protect the convoys.

- The Navy knew all along, but they forgot they knew.

- Is that Donitz' master tactic?

- It's getting late.

Wales, Drake, you're dismissed for the evening. Get some sleep.

Laidlaw, Okell, Rayner. I want you to stay.

- As long as you need us, sir.

- We need to find how the U-boats are getting inside the convoy...

and find a tactic to destroy them.

- Mein Fuhrer, I can strike a decisive blow,

but I need more U-boats.

- U-boat destroyed. - How?

Run the game again. We need to be sure.

- Who devised this tactic? - Wren Jean Laidlaw, sir.

- And do you have a name for it?

- Raspberry. As in, blowing a raspberry at Hitler, sir.

- Well, let's hope it works at sea,

because now Donitz has his 300 U-boats,

and he'll be hell-bent on using them to turn the Atlantic

into a convoy graveyard.

- Imagine the carnage we will sow!

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