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- [Narrator] A message
intercepted from the Germans.
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00:00:05,005 --> 00:00:06,454
- The British are in possession
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00:00:06,454 --> 00:00:09,319
of an essential piece
of intelligence.
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00:00:09,319 --> 00:00:12,529
- [Narrator] That could save
Britain in its darkest hour.
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00:00:12,529 --> 00:00:15,498
- Germany want
Mexico to go to war
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00:00:15,498 --> 00:00:18,156
against the United
States of America.
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00:00:18,156 --> 00:00:21,228
- [Narrator] For World War
I's greatest code breakers,
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deciphering the message
is just the beginning.
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- The British have
got this information
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by spying on the Americans.
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00:00:30,202 --> 00:00:31,928
- [Narrator] Britain's
very survival
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00:00:31,928 --> 00:00:35,207
rests with a team of
eccentric geniuses.
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- He ran down the
corridor and said,
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"Do you want to bring
America into the war, sir?"
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- This was one telegram
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that changed the entire
course of modern history.
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[dramatic music]
[explosions rumble]
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00:00:50,878 --> 00:00:54,226
- [Narrator] These are the
codes that changed our world,
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00:00:54,226 --> 00:00:59,231
bizarre markings, random
letters, and numbers,
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words that make no sense,
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[dramatic music]
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but cracking them
unlocks military secrets,
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decodes ancient civilizations,
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and reveals enemies
in our midst.
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[dramatic music]
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Now we uncover how
they were decoded,
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the genius minds
that broke them,
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and the secrets they reveal.
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[dramatic music]
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[explosions rumble]
[gunfire blasting]
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January 16th, 1917.
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Britain and Germany
have been locked
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in a seemingly unending war
for two and a half years.
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The fiercest fighting
has played out
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on a series of battlefields
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spread across hundreds of miles
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of Northern France
and on into Belgium.
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[explosion rumbles]
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Now, with almost two million
soldiers dead on both sides
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and morale at an all time low,
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Britain's chances of
turning the war around
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are looking hopeless.
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- The bloody cost of the war
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has become apparent to everyone.
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The casualties so far
have been unprecedented.
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Clearly this pace of slaughter
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is not sustainable
for either side.
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One or the other is going to
have to find a new strategy,
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otherwise, this is just gonna
be a slaughter without end.
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[dramatic music]
[explosion rumbles]
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- [Narrator] Then,
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at Britain's lowest
point in the Great War,
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a remote telegram station
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on the westernmost
tip of Britain
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intercepts a suspicious
coded message.
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[telegraph beeping]
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Unknown to the
telegram operator,
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the message conceals
Germany's latest strategy.
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Devised by the
fiercely hard line
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German foreign secretary
Arthur Zimmermann.
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- If you look at these codes,
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you would just see
a string of numbers,
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which would be quite meaningless
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and apparently quite
random as well.
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- [Narrator] The Allies have
intercepted a communication
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from a top German
government official.
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It's in code and
not just any code,
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the most secret code
that Germans possessed.
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- [Narrator] Convinced
his code is un-crackable,
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Zimmermann has sent the telegram
via open diplomatic cables.
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[telegraph beeping]
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But he's underestimated
Britain's intelligence
capabilities.
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[dramatic music]
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Located deep within the
old Admiralty building
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in Whitehall, London,
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is a top secret organization
known as Room 40.
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- This was a pioneering
intelligence operation
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00:04:06,660 --> 00:04:09,110
looking at mainly Naval signals,
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tactical information to see
where the shipping roots were
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00:04:12,217 --> 00:04:13,977
and where the
Germans were forming.
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But increasingly they began
to pick up other signals,
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looking at different aspects
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of the German war
effort and strategy.
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- And they're
particularly interested
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in these secret messages
sent by the Germans.
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Code making and code breaking
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have arrived at modern warfare,
and they're going to stay.
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[suspenseful music]
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- [Narrator] Room 40 is
made up of a brilliant
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if eccentric mix of linguists,
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classical scholars,
and puzzle addicts,
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and they're about to prove vital
in the war against Germany.
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- This is their real strength
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that it's a diversity
of expertise,
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a diversity of brain power.
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Different people, solving
puzzles in different ways
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that can lead some really
innovative solutions.
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- You're dealing with
a small team of people,
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half a dozen at
most, in one office,
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who would be quietly working
with pencil and paper,
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trying to understand
these messages
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and working out the way
in which decode worked.
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- [Narrator] Members
of this crack team
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include Nigel de Grey, a
brilliant cryptographer,
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so mild-mannered, they
call him the dormouse.
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Alfred Dilwyn Knox, or Dilly,
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a classic scholar whose best
work comes while soaking
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00:05:37,129 --> 00:05:40,167
in his specially installed
bathtub in Whitehall.
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And the man heading up
this groundbreaking team
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is no less eccentric.
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The director of British
Naval intelligence,
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Captain Sir Reginald
"Blinker" Hall.
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- Blinker Hall,
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who was known to those who
worked with him as Blinker
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because he had a
persistent facial twitch
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was not a professional
cryptographer.
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He was originally a captain
of a battle cruiser.
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He was a Naval man, but
because of ill health,
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they had to assign
him to other duties,
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and I'm sure he saw
this as a step down
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going from being
master and commander
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of one of the great
warships at sea
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to riding herd over a
bunch of puzzle experts
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and mathematicians.
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00:06:27,594 --> 00:06:29,872
But it turns out that
what Blinker Hall
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is going to achieve with Room 40
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00:06:32,012 --> 00:06:34,601
is worth a fleet
of battle cruisers.
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[telegraph beeping]
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- [Narrator] Blinker
Hall's Naval background
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means he knows only too well
the importance of codebreaking.
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Intercepting and
decrypting enemy codes
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can determine how battles
are fought and won.
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- He could see that
signal's intelligence
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was particularly important
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00:06:56,277 --> 00:06:59,936
in providing a detailed
view of the enemy,
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00:06:59,936 --> 00:07:01,490
but also provide information
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which could be used to wrong
foot the enemy as well.
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- Forewarned is forearmed.
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- [Narrator] By the time
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the mysterious German
telegram lands on his desk,
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Blinker Hall's crack
codebreaking team
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has already more than proved
its worth to the war effort.
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[dramatic music]
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[suspenseful music]
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Two years earlier,
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they managed to decode
an encrypted message.
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Revealing the German high seas
fleet was planning an attack
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on British fishing
vessels in the North Sea.
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- There was a plan afoot
for the German Navy
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to set sail and to
attack British trawlers,
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which were thought to be
passing on information
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part of the
intelligence network.
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- [Narrator] The early
warning courtesy of Room 40
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meant the British Royal Navy
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was able to intercept
the German ships
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long before they
reached the trawlers.
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- This led to the
Battle of Dogger Bank,
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which was a victory
for the British.
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[explosions rumble]
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- [Narrator] Two
German ships were sunk
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and nearly a thousand
German sailors lost.
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This early success
cemented Room 40's position
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as a key weapon in the
war against Germany.
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[dramatic music]
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[telegraph beeping]
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But codebreaking is still
a very new military weapon.
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[explosion rumbles]
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At the very start of World War
I, it was a different story.
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A tragic mistake just
months after war broke out,
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highlighted the need for
secret coded transmissions.
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[dramatic music]
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In September, 1914,
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the German Army was
advancing on Paris
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intent on capturing the city,
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but German wireless operators
made a fatal decision
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that cost hundreds of lives.
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- The Germans made
incredible inroads.
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They're on the outskirts of
Paris, but there's a problem.
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They're advancing so quickly
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that they don't have time
to encrypt the messages
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that they're sending
back and forth,
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and they end up sending a
lot of vital information
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right over these radio waves.
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- [Narrator] As the
German military plans
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were openly broadcast,
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operators at an
interception station
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located high up on the Eiffel
Tower were listening in.
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- For the French, that's
intelligence gold.
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They can hear what the
Germans are planning
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before they do it.
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- [Narrator] Germany's
uncoded transmissions
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allowed French intelligence
to forewarn their troops
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and head off the German advance.
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[explosions rumble]
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- They were able to anticipate
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where the Germans were going
to allocate their troops,
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00:10:02,843 --> 00:10:04,983
where they were going to
put their primary attacks,
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00:10:04,983 --> 00:10:06,260
and make sure they had forces
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00:10:06,260 --> 00:10:08,746
in place to counter
those attacks.
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[dramatic music]
[explosions rumble]
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- [Narrator] The Germans
were forced to retreat
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and Paris left untouched.
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- This carelessness born
out of speed and necessity
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00:10:20,689 --> 00:10:23,277
ends up costing the
Germans many lives.
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00:10:26,384 --> 00:10:30,250
The defense of Paris was a
key turning point in the war.
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00:10:30,250 --> 00:10:31,492
If the Germans had been able
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00:10:31,492 --> 00:10:33,667
to capture Paris,
take France out,
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the whole history of the
war would've been different.
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[dramatic music]
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- [Narrator] The result of the
disastrous offensive on Paris
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is that both Germany and Britain
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develop their own form of code.
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00:10:50,063 --> 00:10:53,549
Swapping letters,
words, and phrases
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with other words or
numbers from a code book.
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00:10:57,795 --> 00:11:00,694
- The code book works
like a dictionary.
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00:11:00,694 --> 00:11:04,318
You have a book with
all the common words,
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00:11:04,318 --> 00:11:08,978
and if you want to encrypt the
word, you need to look it up.
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00:11:08,978 --> 00:11:11,636
[suspenseful music]
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00:11:11,636 --> 00:11:15,329
[explosions rumble]
220
00:11:15,329 --> 00:11:18,263
- [Narrator] Now almost
two and a half years on,
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coded messages are being used
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00:11:19,989 --> 00:11:23,268
by both sides for every
military maneuver,
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00:11:24,373 --> 00:11:28,342
as well as top secret
communications,
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like the one intercepted at
the Cornish relay station.
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00:11:31,932 --> 00:11:34,694
[dramatic music]
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00:11:36,385 --> 00:11:39,353
[explosions rumble]
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At this stage in the war,
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any intelligence on
the enemy's next move
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could be the difference
between winning and losing.
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So, as soon as the mysterious
telegram arrives in Room 40,
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00:11:53,574 --> 00:11:57,233
Blinker Hall's team races
to unlock its contents.
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00:12:00,029 --> 00:12:03,343
- The Allies and the central
powers are exhausted.
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00:12:03,343 --> 00:12:05,621
They're running out of people
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00:12:05,621 --> 00:12:08,175
and they're running
out of resources.
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00:12:08,175 --> 00:12:09,383
[explosion rumbles]
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00:12:09,383 --> 00:12:12,076
- [Narrator] As the
death toll rises daily,
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00:12:12,076 --> 00:12:14,492
Britain is facing
a serious problem.
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00:12:15,493 --> 00:12:17,495
There are simply not enough men
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00:12:17,495 --> 00:12:20,774
to replace the injured
and fallen troops.
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00:12:20,774 --> 00:12:22,845
- The original British Forces
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00:12:22,845 --> 00:12:27,056
were well trained professional
soldiers, but by 1917,
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00:12:27,056 --> 00:12:29,956
the casualties have been so high
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00:12:29,956 --> 00:12:31,474
that the majority
of British troops
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00:12:31,474 --> 00:12:33,580
are going to be conscripts,
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00:12:33,580 --> 00:12:37,308
and they're gonna
have relatively low
levels of training.
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00:12:37,308 --> 00:12:40,380
They just don't
have the experience.
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00:12:40,380 --> 00:12:44,039
World War I has
become a meat grinder
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00:12:44,039 --> 00:12:45,488
and these new conscripts
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00:12:45,488 --> 00:12:50,286
are going to be thrown
into the mix and ground up.
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00:12:50,286 --> 00:12:53,324
[explosion rumbles]
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00:12:53,324 --> 00:12:57,328
- [Narrator] Making matters
worse, food, fuel, and weapons
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00:12:57,328 --> 00:13:00,020
are also in increasingly
short supply.
253
00:13:01,470 --> 00:13:04,507
- World War I is a
war of logistics.
254
00:13:04,507 --> 00:13:06,544
It's literally who
has more material,
255
00:13:06,544 --> 00:13:08,788
who can last the longest.
256
00:13:09,858 --> 00:13:11,825
- [Narrator] The
reliance on outside help
257
00:13:11,825 --> 00:13:14,241
is becoming ever more critical.
258
00:13:14,241 --> 00:13:17,762
[dramatic music]
259
00:13:17,762 --> 00:13:20,661
The only thing now
keeping Britain afloat
260
00:13:20,661 --> 00:13:22,353
is help from America.
261
00:13:24,010 --> 00:13:25,943
- America is neutral
at this point,
262
00:13:25,943 --> 00:13:29,084
but they are providing a
vital service to Britain
263
00:13:29,084 --> 00:13:32,708
by sending supplies, both
of arms and ammunition,
264
00:13:32,708 --> 00:13:36,850
but also of general
materials and food resources.
265
00:13:38,540 --> 00:13:41,061
- The most crucial
transportation link
266
00:13:41,061 --> 00:13:44,271
is across the vast
stretches of the Atlantic,
267
00:13:44,271 --> 00:13:47,136
bringing the massive
material resources
268
00:13:47,136 --> 00:13:48,793
of the United States,
269
00:13:48,793 --> 00:13:51,727
to where the Allies need the
most on the Western Front.
270
00:13:53,142 --> 00:13:55,835
All the help from the United
States doesn't come for free.
271
00:13:55,835 --> 00:13:58,216
Britain has to pay
for these goods,
272
00:13:58,216 --> 00:14:00,736
either up front or
by taking out loans,
273
00:14:00,736 --> 00:14:03,152
and the debt is rising.
274
00:14:05,845 --> 00:14:07,191
- [Narrator] American supplies
275
00:14:07,191 --> 00:14:10,125
are not going to be
enough to win the war.
276
00:14:11,643 --> 00:14:16,096
Britain needs more
men and more money.
277
00:14:16,096 --> 00:14:20,480
Its only hope of survival
is America joining the war,
278
00:14:20,480 --> 00:14:24,725
but the US president
refuses to budge.
279
00:14:24,725 --> 00:14:28,557
- America at the time, sees
itself as the peace broker.
280
00:14:28,557 --> 00:14:32,388
This is a European conflict
that it would rather see end.
281
00:14:32,388 --> 00:14:33,873
They're not going to throw
282
00:14:33,873 --> 00:14:35,978
their young men into
that meat grinder.
283
00:14:35,978 --> 00:14:38,981
[explosion rumbles]
284
00:14:42,605 --> 00:14:43,813
- [Narrator] The
British government
285
00:14:43,813 --> 00:14:45,988
is now desperate
for any intelligence
286
00:14:45,988 --> 00:14:48,266
that might persuade
the American president
287
00:14:48,266 --> 00:14:49,958
to change his mind.
288
00:14:51,821 --> 00:14:54,548
So, the pressure's on
Blinker Hall's team
289
00:14:54,548 --> 00:14:56,274
to deliver the goods.
290
00:14:58,483 --> 00:15:00,623
Within 24 hours of
getting his hands
291
00:15:00,623 --> 00:15:02,798
on the encrypted telegram,
292
00:15:02,798 --> 00:15:05,835
Room 40's chief
codebreaker, Nigel de Grey,
293
00:15:05,835 --> 00:15:09,218
has identified key
information in the code.
294
00:15:11,600 --> 00:15:14,051
- Although to the
nonprofessional,
295
00:15:14,051 --> 00:15:16,674
these intercepted
messages looked like
296
00:15:16,674 --> 00:15:19,263
just a jumble of
meaningless numbers.
297
00:15:19,263 --> 00:15:23,543
To those who are working day
in, day out on these messages,
298
00:15:23,543 --> 00:15:26,580
they can spot certain
patterns that occur.
299
00:15:28,513 --> 00:15:30,343
- [Narrator] After
almost three years
300
00:15:30,343 --> 00:15:33,553
of analyzing Germany's
secret communications,
301
00:15:33,553 --> 00:15:35,313
de Grey is able to identify
302
00:15:35,313 --> 00:15:38,834
which code has been used to
encrypt the original message
303
00:15:38,834 --> 00:15:43,045
simply by the presence
of certain number groups,
304
00:15:43,045 --> 00:15:47,601
and he's got lucky
with this message.
305
00:15:47,601 --> 00:15:50,328
[dramatic music]
306
00:15:51,260 --> 00:15:54,091
It's been encrypted with a code
307
00:15:54,091 --> 00:15:59,096
already known to the Room
40 codebreakers as 0075.
308
00:16:01,408 --> 00:16:04,791
This number is included at
the start of the message
309
00:16:04,791 --> 00:16:07,897
and is the key the receiver
needs to decipher it.
310
00:16:09,796 --> 00:16:12,212
0075 is the latest variant
311
00:16:12,212 --> 00:16:16,320
of a code Germany has been
using since the war began.
312
00:16:16,320 --> 00:16:21,325
And by 1917, it's
being used to encrypt
313
00:16:22,809 --> 00:16:25,915
Germany's most top secret
diplomatic communications.
314
00:16:25,915 --> 00:16:27,641
- It's using a
top priority code,
315
00:16:27,641 --> 00:16:30,437
which shows that
it almost portrays
316
00:16:30,437 --> 00:16:32,163
that this is an
important message.
317
00:16:34,131 --> 00:16:37,065
- [Narrator] De Grey knows
that every sequence of numbers
318
00:16:37,065 --> 00:16:39,032
relates to a specific word,
319
00:16:39,032 --> 00:16:44,037
but to know what that word
is requires a code book.
320
00:16:45,728 --> 00:16:48,283
- So, you have a
plain language word,
321
00:16:48,283 --> 00:16:52,425
ship, town, cloud, destination,
322
00:16:53,840 --> 00:16:56,808
and for each entry of those
plain language in the code book,
323
00:16:56,808 --> 00:16:58,500
you then have a
string of numbers.
324
00:17:00,640 --> 00:17:02,228
- [Narrator] Once encrypted,
325
00:17:02,228 --> 00:17:05,576
the message is then
transmitted in Morse code
326
00:17:05,576 --> 00:17:08,613
and sent via cable to
the intended recipient,
327
00:17:09,820 --> 00:17:12,928
who also has a copy
of the code book.
328
00:17:12,928 --> 00:17:14,204
[telegraph beeping]
329
00:17:14,204 --> 00:17:15,550
- On receipt of the message,
330
00:17:15,550 --> 00:17:17,967
the operator would look
in a reverse code book,
331
00:17:17,967 --> 00:17:20,003
see the number,
look up the number,
332
00:17:20,003 --> 00:17:23,076
and then find out the
plain language word.
333
00:17:23,076 --> 00:17:24,491
[telegraph beeping]
334
00:17:24,491 --> 00:17:26,147
- [Narrator]
Believing their code
335
00:17:26,147 --> 00:17:27,701
to be un-crackable
without a code book,
336
00:17:27,701 --> 00:17:29,289
Germany now transmits
337
00:17:29,289 --> 00:17:32,810
all of its most top secret
diplomatic communications
338
00:17:32,810 --> 00:17:36,055
using code 0075,
339
00:17:36,055 --> 00:17:39,920
but its faith in its
code is badly misplaced.
340
00:17:41,301 --> 00:17:43,993
- All the German code books
had certain similarities
341
00:17:43,993 --> 00:17:46,030
and there were features
which were common
342
00:17:47,100 --> 00:17:48,860
to all types of code book.
343
00:17:48,860 --> 00:17:50,724
So, once you started working out
344
00:17:50,724 --> 00:17:54,694
how the Germans designed
their code books,
345
00:17:54,694 --> 00:17:55,971
then you would have insight
346
00:17:55,971 --> 00:17:58,007
into a new code book
when it came along.
347
00:17:59,181 --> 00:18:01,045
- [Narrator] Since
the war broke out,
348
00:18:01,045 --> 00:18:03,530
Blinker Hall's team
has managed to get hold
349
00:18:03,530 --> 00:18:06,085
of several old
German code books,
350
00:18:06,085 --> 00:18:08,294
which are now
proving invaluable.
351
00:18:09,778 --> 00:18:13,126
- The Germans thought their
codes were fairly secure,
352
00:18:13,126 --> 00:18:16,198
but in fact, they were
very, very simple codes
353
00:18:16,198 --> 00:18:19,028
and they weren't
changed often enough.
354
00:18:20,616 --> 00:18:24,655
- Very often, the code
makers used one code book
355
00:18:24,655 --> 00:18:27,554
as the basis for the next one,
356
00:18:27,554 --> 00:18:29,901
and so if they knew the one,
357
00:18:29,901 --> 00:18:34,147
it wasn't too difficult for
them to guess the next one.
358
00:18:34,147 --> 00:18:35,493
[suspenseful music]
359
00:18:35,493 --> 00:18:37,944
- That critical
error by the Germans
360
00:18:37,944 --> 00:18:41,568
now plays directly into
Blinker Hall's hands.
361
00:18:43,087 --> 00:18:44,951
[telegraph beeping]
362
00:18:44,951 --> 00:18:47,264
The codebreakers already
know the message is German
363
00:18:47,264 --> 00:18:49,369
and highly top secret.
364
00:18:50,784 --> 00:18:54,443
It was heading on a cable
from Berlin to Washington DC.
365
00:18:56,273 --> 00:18:59,207
The code used means it's
a diplomatic communication
366
00:18:59,207 --> 00:19:03,935
and they're about to find
out exactly who sent it,
367
00:19:03,935 --> 00:19:08,664
because the message's
numbers hold another clue.
368
00:19:10,321 --> 00:19:13,635
De Grey has discovered that
the final five digit number
369
00:19:13,635 --> 00:19:16,948
in every message is
a signature and code,
370
00:19:18,433 --> 00:19:20,918
and a search of his
comprehensive records
371
00:19:20,918 --> 00:19:22,989
reveals a likely match.
372
00:19:24,163 --> 00:19:26,130
De Grey is certain
that the telegram
373
00:19:26,130 --> 00:19:30,203
has to be from top German
politician Arthur Zimmermann.
374
00:19:32,550 --> 00:19:35,760
- The Room 40 folks work
out that this message
375
00:19:35,760 --> 00:19:38,142
is from the German
foreign secretary,
376
00:19:38,142 --> 00:19:40,524
and the Americans had
always seen Zimmermann
377
00:19:40,524 --> 00:19:44,459
as someone that might
be a good possibility
378
00:19:44,459 --> 00:19:47,220
for brokering this
diplomatic solution
379
00:19:47,220 --> 00:19:49,222
to the bloodshed of
the first World War.
380
00:19:51,500 --> 00:19:54,089
- [Narrator] But as de Grey
and his fellow codebreakers
381
00:19:54,089 --> 00:19:57,610
begin to unscramble
fragments of the message,
382
00:19:57,610 --> 00:20:01,890
it becomes clear that America
couldn't have been more wrong
383
00:20:01,890 --> 00:20:04,755
about Zimmermann's ambitions.
384
00:20:04,755 --> 00:20:08,172
[dramatic music]
385
00:20:08,172 --> 00:20:10,347
From what they can make out,
386
00:20:10,347 --> 00:20:11,900
it seems that Zimmermann
387
00:20:11,900 --> 00:20:15,386
is encouraging more,
not less aggression.
388
00:20:17,871 --> 00:20:20,943
Their initial decoding
suggests Germany is planning
389
00:20:20,943 --> 00:20:24,740
to unleash deadly U-boat
attacks in British waters.
390
00:20:27,018 --> 00:20:29,228
And that means no vessel,
391
00:20:29,228 --> 00:20:32,852
not even neutral American
ships will be spared.
392
00:20:33,922 --> 00:20:37,028
- Unrestricted
submarine warfare means
393
00:20:37,028 --> 00:20:39,307
that they can target any ship
394
00:20:39,307 --> 00:20:42,102
regardless of what
flag it's flying,
395
00:20:42,102 --> 00:20:43,483
if they have good evidence
396
00:20:43,483 --> 00:20:46,521
to believe it's
carrying war material.
397
00:20:48,005 --> 00:20:52,009
- The idea was to destroy
the British supply lines
398
00:20:52,009 --> 00:20:56,047
of ammunition,
machinery and food.
399
00:20:56,047 --> 00:20:59,016
[explosion rumbles]
400
00:21:02,053 --> 00:21:04,746
- [Narrator] Nigel de
Grey immediately realizes
401
00:21:04,746 --> 00:21:07,266
how explosive this
information is.
402
00:21:08,922 --> 00:21:10,786
The fact that American ships
403
00:21:10,786 --> 00:21:13,617
will no longer be
safe in the Atlantic,
404
00:21:13,617 --> 00:21:17,690
could be just what Britain
needs to finally persuade the US
405
00:21:17,690 --> 00:21:20,520
to come to its aid
and join the war.
406
00:21:22,142 --> 00:21:24,213
Because the telegram's contents
407
00:21:24,213 --> 00:21:26,664
are a blatant disregard
of an agreement
408
00:21:26,664 --> 00:21:28,528
Germany made with the US
409
00:21:28,528 --> 00:21:31,911
following a terrible
military blunder.
410
00:21:31,911 --> 00:21:34,948
[suspenseful music]
411
00:21:38,504 --> 00:21:40,471
A year into the war,
412
00:21:40,471 --> 00:21:42,922
British Navy ships
formed a blockade
413
00:21:42,922 --> 00:21:46,857
to stop any supplies
reaching German shores.
414
00:21:46,857 --> 00:21:51,033
The intention to starve
Germany out of the war.
415
00:21:51,033 --> 00:21:53,726
- The Germans are blockaded
416
00:21:53,726 --> 00:21:56,211
and there's only a
limited amount of supplies
417
00:21:56,211 --> 00:21:57,833
that they have
available to them.
418
00:21:58,765 --> 00:22:00,319
- [Narrator] In retaliation,
419
00:22:00,319 --> 00:22:01,941
The German Navy was ordered
420
00:22:01,941 --> 00:22:04,599
to seek and destroy
any neutral ship
421
00:22:04,599 --> 00:22:07,326
that was supplying Britain
with war materials.
422
00:22:08,603 --> 00:22:10,225
- The Germans are
gonna try to set up
423
00:22:10,225 --> 00:22:13,193
their own response
to the blockade.
424
00:22:13,193 --> 00:22:15,955
They're gonna deploy a
terrifying new weapon,
425
00:22:17,059 --> 00:22:20,062
the Unterseeboot, or U-boat,
426
00:22:20,062 --> 00:22:23,756
and they're going to use
that, not to target warships,
427
00:22:23,756 --> 00:22:26,655
but to target the
vital supply lines
428
00:22:26,655 --> 00:22:31,246
that are bringing in food,
and fuel, and ammunition,
429
00:22:31,246 --> 00:22:34,007
and the Germans realize
430
00:22:34,007 --> 00:22:37,010
if they can choke off
that vital supply line,
431
00:22:37,010 --> 00:22:38,633
that'll be enough
to end the war.
432
00:22:39,875 --> 00:22:42,706
- [Narrator] But
on May 7th, 1915,
433
00:22:42,706 --> 00:22:45,191
off the coast of
Southern Ireland,
434
00:22:45,191 --> 00:22:47,676
a submerged German
U-boat torpedoed
435
00:22:47,676 --> 00:22:50,955
what it claimed was
an enemy troop ship.
436
00:22:50,955 --> 00:22:53,372
[dramatic music]
437
00:22:53,372 --> 00:22:54,165
It wasn't.
438
00:22:55,788 --> 00:22:58,411
[ominous music]
439
00:23:00,413 --> 00:23:03,451
The Lusitania was a
British ocean liner
440
00:23:03,451 --> 00:23:05,660
carrying civilian passengers.
441
00:23:07,386 --> 00:23:11,631
Over 1,200 innocent
people died in the attack.
442
00:23:11,631 --> 00:23:14,393
128 were American.
443
00:23:15,601 --> 00:23:16,878
- Civilians were
not supposed to be
444
00:23:16,878 --> 00:23:19,846
targeted intentionally
in war time,
445
00:23:19,846 --> 00:23:22,193
and this is why the
sinking of the Lusitania
446
00:23:22,193 --> 00:23:25,093
stands out as such a big deal.
447
00:23:25,093 --> 00:23:28,061
It is treated as an
act of barbarism,
448
00:23:28,061 --> 00:23:32,065
of brutality, of
unnecessary cruelty.
449
00:23:34,447 --> 00:23:36,311
- [Narrator] America was enraged
450
00:23:36,311 --> 00:23:38,865
by the attack on the Lusitania,
451
00:23:38,865 --> 00:23:43,422
but Germany claimed it was
a case of mistaken identity
452
00:23:43,422 --> 00:23:45,596
and vowed to do better.
453
00:23:46,735 --> 00:23:49,531
- The Germans realize
that the Americans
454
00:23:49,531 --> 00:23:53,155
entering the war would
be a game changer.
455
00:23:53,155 --> 00:23:57,505
So, the Germans make a promise
that they will redouble
456
00:23:57,505 --> 00:23:59,921
their efforts to make
proper identification,
457
00:23:59,921 --> 00:24:02,717
to make sure any targets
engaged by the U-boats
458
00:24:02,717 --> 00:24:05,789
are legitimate military targets.
459
00:24:05,789 --> 00:24:08,101
- [Narrator] Despite the
devastating loss of life
460
00:24:08,101 --> 00:24:11,070
on the Lusitania,
President Woodrow Wilson
461
00:24:11,070 --> 00:24:13,141
accepted Germany's new policy,
462
00:24:13,141 --> 00:24:18,146
and America stayed on the
sidelines of World War I.
463
00:24:19,285 --> 00:24:20,666
- The sentiment in America
464
00:24:20,666 --> 00:24:22,737
was very strongly
against getting involved,
465
00:24:22,737 --> 00:24:24,497
so this promise
really gives Wilson
466
00:24:24,497 --> 00:24:27,155
an excuse to keep America out.
467
00:24:29,571 --> 00:24:31,193
- [Woodrow] I know that
you are depending on me
468
00:24:31,193 --> 00:24:33,472
to keep this nation out of war.
469
00:24:33,472 --> 00:24:35,266
So far, I have done so,
470
00:24:35,266 --> 00:24:39,857
and I pledge you my word
that God helping me, I will.
471
00:24:39,857 --> 00:24:44,552
- The public line was "Keep
America Out of the War,"
472
00:24:44,552 --> 00:24:47,002
supply the Allies with
the equipment they need,
473
00:24:47,002 --> 00:24:50,661
but don't send
American boys overseas.
474
00:24:51,869 --> 00:24:53,664
[explosions rumble]
[somber horn music]
475
00:24:53,664 --> 00:24:56,667
And they can see the casualty
numbers as clearly as anybody
476
00:24:56,667 --> 00:25:01,430
and to send over American
men into that mess,
477
00:25:01,430 --> 00:25:05,331
into what's really a European
war from their perspective,
478
00:25:05,331 --> 00:25:07,713
it's just not
politically tenable.
479
00:25:07,713 --> 00:25:10,163
[dramatic music]
480
00:25:10,163 --> 00:25:13,166
- [Narrator] Two years after
the sinking of the Lusitania,
481
00:25:13,166 --> 00:25:15,583
President Wilson has
won a second term
482
00:25:15,583 --> 00:25:18,517
with his promise
to stay neutral.
483
00:25:18,517 --> 00:25:19,794
[boots stomping]
484
00:25:19,794 --> 00:25:21,830
Britain needs some
serious leverage.
485
00:25:21,830 --> 00:25:25,040
If Wilson is going to
perform a drastic U-turn
486
00:25:25,040 --> 00:25:28,285
and send American
soldiers to war.
487
00:25:28,285 --> 00:25:31,012
[dramatic music]
488
00:25:32,531 --> 00:25:36,362
In Room 40, even
mild-mannered Nigel de Grey
489
00:25:36,362 --> 00:25:38,640
believes what's
been decoded so far
490
00:25:38,640 --> 00:25:42,541
from the Zimmermann Telegram
could prove to be crucial.
491
00:25:44,853 --> 00:25:46,545
- He ran down the corridor
492
00:25:46,545 --> 00:25:49,824
to Blinker Hall's
office and said to him,
493
00:25:49,824 --> 00:25:52,827
"Do you want to bring
America into the war, sir?"
494
00:25:52,827 --> 00:25:55,761
To which Blinker Hall
replied, "Yes, why?"
495
00:25:55,761 --> 00:25:58,073
Well, we've got the
telegram that might do it.
496
00:25:59,178 --> 00:26:00,835
- For those who do want to see
497
00:26:00,835 --> 00:26:03,354
America get off the sidelines,
498
00:26:03,354 --> 00:26:05,598
this could be the thing
that makes it happen.
499
00:26:06,772 --> 00:26:08,912
[suspenseful music]
500
00:26:08,912 --> 00:26:11,500
- [Narrator] But
there's a problem.
501
00:26:11,500 --> 00:26:13,468
In fact, there are several.
502
00:26:14,952 --> 00:26:18,818
- The first part is, it's
only been partially decoded,
503
00:26:18,818 --> 00:26:21,234
so there's a huge risk moving
forward with this information
504
00:26:21,234 --> 00:26:24,548
before you have all the
information available.
505
00:26:24,548 --> 00:26:27,171
- [Narrator] The second
issue is security.
506
00:26:27,171 --> 00:26:29,657
If even partial
contents are released,
507
00:26:29,657 --> 00:26:33,005
the Germans will know the
British have cracked their code.
508
00:26:34,489 --> 00:26:37,388
- If they reveal that they
can read any of that code,
509
00:26:37,388 --> 00:26:39,736
the Germans will immediately
change their system overnight,
510
00:26:39,736 --> 00:26:42,117
and all of the
British decoding work
511
00:26:42,117 --> 00:26:43,947
done in Room 40 will be wasted.
512
00:26:43,947 --> 00:26:46,190
They'll have to start
from scratch again.
513
00:26:46,190 --> 00:26:47,916
[dramatic music]
514
00:26:47,916 --> 00:26:51,264
- [Narrator] But the third issue
is the hardest to overcome.
515
00:26:53,232 --> 00:26:57,616
It's the way the message was
intercepted in the first place.
516
00:26:57,616 --> 00:27:00,135
- The British have
got this information
517
00:27:00,135 --> 00:27:02,897
by spying on the Americans.
518
00:27:02,897 --> 00:27:06,038
[telegraph beeping]
519
00:27:06,038 --> 00:27:08,765
[suspenseful music]
520
00:27:08,765 --> 00:27:10,214
- [Narrator] The
root of the problem
521
00:27:10,214 --> 00:27:14,356
dates back two and a
half years to July, 1914,
522
00:27:14,356 --> 00:27:17,394
just hours after World
War I was declared.
523
00:27:18,706 --> 00:27:20,673
In a covert operation,
524
00:27:20,673 --> 00:27:23,952
a cable laying ship slipped
out of the port of Dover
525
00:27:23,952 --> 00:27:25,713
on Britain's south coast.
526
00:27:27,093 --> 00:27:30,165
It made its way to the middle
of the English channel,
527
00:27:30,165 --> 00:27:32,029
weighing anchor directly above
528
00:27:32,029 --> 00:27:34,860
a series of German
owned telegram cables,
529
00:27:34,860 --> 00:27:38,657
connecting Germany to America
under the Atlantic Ocean.
530
00:27:41,142 --> 00:27:44,007
The crew of the CS
Alert then began
531
00:27:44,007 --> 00:27:47,458
systematically tearing up
every cable from the seabed.
532
00:27:49,012 --> 00:27:50,634
- So the transatlantic cables
533
00:27:50,634 --> 00:27:52,015
are one of the great feats
534
00:27:52,015 --> 00:27:55,225
of communications
technology in that period.
535
00:27:55,225 --> 00:27:58,159
There are five German cables
going across the Atlantic
536
00:27:58,159 --> 00:28:00,575
and the CS Alert
severs all of them.
537
00:28:02,025 --> 00:28:05,097
- [Narrator] For Britain, this
was a tactical master stroke.
538
00:28:05,097 --> 00:28:08,583
For Germany, a
monumental disaster.
539
00:28:08,583 --> 00:28:13,588
- All German communications
internationally were cut off.
540
00:28:15,038 --> 00:28:16,798
- The modern equivalent would
be, as soon as war breaks out,
541
00:28:16,798 --> 00:28:18,593
shooting down the
enemy satellites.
542
00:28:18,593 --> 00:28:21,389
You are blinding them
and deafening them.
543
00:28:23,667 --> 00:28:25,048
- [Narrator] With
its vital lines
544
00:28:25,048 --> 00:28:27,360
of communication out of action,
545
00:28:27,360 --> 00:28:30,847
Germany had no choice
but to seek outside help.
546
00:28:32,020 --> 00:28:33,366
- If they want to communicate
547
00:28:33,366 --> 00:28:35,714
with their representatives
in Washington,
548
00:28:35,714 --> 00:28:37,577
they're going to have
to use the cables
549
00:28:37,577 --> 00:28:39,441
that belong to another country.
550
00:28:41,340 --> 00:28:43,411
- [Narrator] By 1917,
551
00:28:43,411 --> 00:28:46,138
any telegram sent between
Germany and America
552
00:28:46,138 --> 00:28:48,727
must travel along
the cable route
553
00:28:48,727 --> 00:28:51,419
that passes through
British waters,
554
00:28:51,419 --> 00:28:53,593
[telegraph beeping]
555
00:28:53,593 --> 00:28:56,804
and wireless operators at
the remote telegram station
556
00:28:56,804 --> 00:28:59,392
on the Cornish coast are
secretly tapping the line,
557
00:29:00,808 --> 00:29:04,501
intercepting every message
that uses the underwater cable
558
00:29:04,501 --> 00:29:06,296
linking Britain to America.
559
00:29:07,711 --> 00:29:10,369
And that's why intercepting
the Zimmermann telegram
560
00:29:10,369 --> 00:29:12,681
is such a big deal.
561
00:29:12,681 --> 00:29:15,029
[suspenseful music]
562
00:29:15,029 --> 00:29:17,479
The message the British
codebreakers hope
563
00:29:17,479 --> 00:29:20,137
will force America into the war
564
00:29:20,137 --> 00:29:22,070
has been picked up
by eavesdropping
565
00:29:22,070 --> 00:29:24,210
on supposedly secure lines
566
00:29:24,210 --> 00:29:28,318
reserved for highly
confidential diplomatic traffic.
567
00:29:29,526 --> 00:29:31,735
- America had agreed
to let the Germans
568
00:29:31,735 --> 00:29:33,668
continue to use these cables
569
00:29:33,668 --> 00:29:37,189
specifically for
peace negotiations.
570
00:29:37,189 --> 00:29:40,468
But of course, that
wasn't entirely what
they were used for.
571
00:29:40,468 --> 00:29:43,264
- Britain had been
decoding American messages
572
00:29:43,264 --> 00:29:44,886
from late 1915,
573
00:29:44,886 --> 00:29:47,268
and so were keeping an
eye on what was going on
574
00:29:47,268 --> 00:29:49,960
and rapidly saw
the German messages
575
00:29:49,960 --> 00:29:53,136
being passed bundled in
with American messages.
576
00:29:54,240 --> 00:29:55,310
- [Narrator] Germany
may have been
577
00:29:55,310 --> 00:29:57,899
abusing America's goodwill,
578
00:29:57,899 --> 00:30:02,455
but Britain has been snooping
on its potential ally.
579
00:30:02,455 --> 00:30:05,286
- So, the British have to
be delicate about this.
580
00:30:05,286 --> 00:30:07,564
The last thing they want
is for the Americans
581
00:30:07,564 --> 00:30:11,188
to think that they
are being spied on.
582
00:30:11,188 --> 00:30:13,915
[dramatic music]
583
00:30:16,815 --> 00:30:18,782
- [Narrator] Even though
Blinker Hall's team
584
00:30:18,782 --> 00:30:21,509
has decoded enough of
the Zimmermann telegram
585
00:30:21,509 --> 00:30:23,373
to make the case that Germany
586
00:30:23,373 --> 00:30:24,926
is about to start targeting
587
00:30:24,926 --> 00:30:28,309
American merchant
ships in the Atlantic,
588
00:30:28,309 --> 00:30:33,314
they need a rock solid cover
story to explain how they know.
589
00:30:35,626 --> 00:30:37,628
- The British are in possession
590
00:30:37,628 --> 00:30:40,804
of an essential piece
of intelligence.
591
00:30:40,804 --> 00:30:45,015
But if they're not extremely
cautious in how they use it,
592
00:30:45,015 --> 00:30:47,224
they run the risk
of offending someone
593
00:30:47,224 --> 00:30:48,847
they're seeking as an ally.
594
00:30:48,847 --> 00:30:51,263
- [Narrator] Blinker Hall
knows now is the time
595
00:30:51,263 --> 00:30:55,784
to refer up and share Room
40's findings with his boss,
596
00:30:55,784 --> 00:30:58,787
the British Prime Minister,
David Lloyd George.
597
00:31:00,686 --> 00:31:03,654
Despite Britain
desperately needing help,
598
00:31:03,654 --> 00:31:06,795
Lloyd George believes
the timing isn't right,
599
00:31:08,280 --> 00:31:11,939
revealing the secretly
intercepted message
to America now
600
00:31:11,939 --> 00:31:14,734
could be catastrophic
for future relations.
601
00:31:16,184 --> 00:31:20,706
So, he decides the only
thing to do is wait.
602
00:31:20,706 --> 00:31:22,673
- If he just sits on this
603
00:31:22,673 --> 00:31:24,952
and Germany goes through
with what they're threatening
604
00:31:24,952 --> 00:31:26,815
unrestricted submarine warfare,
605
00:31:26,815 --> 00:31:28,817
that might bring
America into the war,
606
00:31:28,817 --> 00:31:31,579
and they have good
reason to believe that.
607
00:31:31,579 --> 00:31:34,202
[dramatic music]
[explosion rumbles]
608
00:31:34,202 --> 00:31:37,343
- [Narrator] On
February 1st, 1917,
609
00:31:37,343 --> 00:31:40,519
two weeks after the
telegram was intercepted,
610
00:31:40,519 --> 00:31:43,108
Germany launches the offensive
611
00:31:43,108 --> 00:31:46,835
Zimmermann outlined
in his coded telegram.
612
00:31:46,835 --> 00:31:50,356
Unrestricted U-boat
warfare in the Atlantic
613
00:31:50,356 --> 00:31:52,496
is a clear betrayal
of the agreement
614
00:31:52,496 --> 00:31:54,740
made between
Germany and America,
615
00:31:56,224 --> 00:31:57,777
but will this aggression
616
00:31:57,777 --> 00:32:00,815
be enough to bring
America into the war?
617
00:32:01,885 --> 00:32:04,577
[dramatic music]
618
00:32:09,134 --> 00:32:11,170
In Washington, D.C.,
619
00:32:11,170 --> 00:32:15,002
President Wilson's reaction
to Germany's hostile actions
620
00:32:15,002 --> 00:32:16,486
is a long way
621
00:32:16,486 --> 00:32:18,522
from what the British
government is hoping for.
622
00:32:19,730 --> 00:32:20,939
- And though America breaks off
623
00:32:20,939 --> 00:32:22,941
diplomatic relations in protest,
624
00:32:22,941 --> 00:32:25,667
they don't immediately enter
on the side of the Allies.
625
00:32:27,290 --> 00:32:31,190
- [Narrator] The wait and
see approach has backfired,
626
00:32:31,190 --> 00:32:33,399
but there's still
one last chance
627
00:32:33,399 --> 00:32:36,506
to change the US
president's mind.
628
00:32:36,506 --> 00:32:38,266
- The unrestricted
submarine warfare
629
00:32:38,266 --> 00:32:40,130
didn't bring America in.
630
00:32:40,130 --> 00:32:43,237
But what about the other
part of the message?
631
00:32:43,237 --> 00:32:46,240
[suspenseful music]
632
00:32:48,311 --> 00:32:49,829
- [Narrator] Back in London,
633
00:32:49,829 --> 00:32:52,971
Blinker Hall's team is
now working day and night
634
00:32:52,971 --> 00:32:54,903
to decode the rest
of the message
635
00:32:54,903 --> 00:32:57,630
in the hope it contains
more information
636
00:32:57,630 --> 00:32:59,978
to bring America into the war.
637
00:33:03,050 --> 00:33:06,708
As Nigel de Gray unpicks
more and more fragments,
638
00:33:07,744 --> 00:33:09,918
he discovers
something unexpected.
639
00:33:11,920 --> 00:33:14,993
Although the telegram
was heading for America,
640
00:33:14,993 --> 00:33:19,307
the US wasn't the telegram's
final destination.
641
00:33:19,307 --> 00:33:21,792
After reaching Washington D.C.,
642
00:33:21,792 --> 00:33:26,004
the Zimmermann telegram
was forwarded on to Mexico.
643
00:33:28,489 --> 00:33:32,010
And this immediately
raises a red flag.
644
00:33:33,425 --> 00:33:37,670
- Germany was making
diplomatic overtures to Mexico,
645
00:33:37,670 --> 00:33:40,052
which appeared to be
trying to entice them
646
00:33:40,052 --> 00:33:42,537
into joining the
war on German side.
647
00:33:44,160 --> 00:33:46,714
- [Narrator] And the
more information the
team unscrambles,
648
00:33:46,714 --> 00:33:50,373
the more shocking the
intelligence becomes.
649
00:33:50,373 --> 00:33:53,997
- They can only understand
patches of that code,
650
00:33:53,997 --> 00:33:55,757
and yet the
potential is massive.
651
00:33:57,242 --> 00:33:58,829
- [Narrator] They want Mexico
652
00:33:58,829 --> 00:34:02,833
to go to war against the
United States of America.
653
00:34:02,833 --> 00:34:04,456
- This has the potential
654
00:34:04,456 --> 00:34:07,631
to change the entire course
of the First World War.
655
00:34:10,393 --> 00:34:12,395
- [Narrator] The German
foreign secretary
656
00:34:12,395 --> 00:34:14,534
is a hard line strategist,
657
00:34:14,534 --> 00:34:17,917
and he's desperate to
see Germany win the war.
658
00:34:19,091 --> 00:34:22,060
He hopes that exploiting
Mexico's lingering anger
659
00:34:22,060 --> 00:34:25,027
with the US over
territory the country lost
660
00:34:25,027 --> 00:34:29,722
to America 70 years
earlier will do just that.
661
00:34:29,722 --> 00:34:31,897
[suspenseful music]
662
00:34:31,897 --> 00:34:35,141
- There's no small number
of people in Mexico
663
00:34:35,141 --> 00:34:39,732
that still see that territory
as Mexican territory,
664
00:34:39,732 --> 00:34:41,734
not American territory.
665
00:34:43,667 --> 00:34:46,187
- [Narrator] Zimmermann
appears to be promising
666
00:34:46,187 --> 00:34:51,018
that Germany will finance a
military invasion of the US,
667
00:34:51,018 --> 00:34:53,746
allowing Mexico to claim back
668
00:34:53,746 --> 00:34:58,613
their lost states of Texas,
Arizona, and New Mexico.
669
00:35:00,477 --> 00:35:02,928
- It is astounding that the
German foreign secretary
670
00:35:02,928 --> 00:35:06,518
would write to the
Mexican authorities,
671
00:35:06,518 --> 00:35:11,109
encouraging them to make war
on the United States of America
672
00:35:11,109 --> 00:35:14,042
and to claim territories
such as Texas
673
00:35:14,042 --> 00:35:16,597
from the United
States of America,
674
00:35:18,046 --> 00:35:20,152
and yet this is precisely
what this telegram does.
675
00:35:20,152 --> 00:35:22,154
[suspenseful music]
676
00:35:22,154 --> 00:35:25,640
- If Blinker Hall and his
team's decoding is correct,
677
00:35:25,640 --> 00:35:27,884
Zimmermann's plan
is a clever one.
678
00:35:29,023 --> 00:35:32,026
A war on home soil
will distract America,
679
00:35:32,026 --> 00:35:36,996
effectively keeping the country
out of World War I for good.
680
00:35:38,515 --> 00:35:39,999
- In effect,
681
00:35:39,999 --> 00:35:44,418
this cable was supporting a
direct attack on American land.
682
00:35:45,626 --> 00:35:47,628
- [Narrator] An
American Mexican war
683
00:35:47,628 --> 00:35:49,630
would also have
the added benefit
684
00:35:49,630 --> 00:35:53,116
that the US supplies
keeping Britain in the war
685
00:35:53,116 --> 00:35:54,635
would dry up.
686
00:35:54,635 --> 00:35:59,157
- It would force America to
redirect all the supplies
687
00:35:59,157 --> 00:36:02,021
it's been sending
across the Atlantic
688
00:36:02,021 --> 00:36:03,644
to the Allied war
effort in Europe,
689
00:36:03,644 --> 00:36:06,164
to defending its own borders.
690
00:36:09,581 --> 00:36:13,032
- [Narrator] Increased
aggression by U-boats
691
00:36:13,032 --> 00:36:14,482
may not have been enough
692
00:36:14,482 --> 00:36:16,760
to change President
Wilson's mind,
693
00:36:17,968 --> 00:36:19,729
but Blinker Hall and
his team are hoping
694
00:36:19,729 --> 00:36:23,595
that the very real threat
of a border war with Mexico
695
00:36:23,595 --> 00:36:25,700
will finally hit home.
696
00:36:25,700 --> 00:36:28,289
[dramatic music]
697
00:36:28,289 --> 00:36:29,463
[explosions rumble]
698
00:36:29,463 --> 00:36:31,361
But as with the
previous intelligence,
699
00:36:31,361 --> 00:36:34,226
they're still facing
the same problem
700
00:36:34,226 --> 00:36:37,747
of how the information was
gathered in the first place,
701
00:36:38,851 --> 00:36:40,336
by British intelligence,
702
00:36:40,336 --> 00:36:43,201
spying on America's
supposedly secure
703
00:36:43,201 --> 00:36:45,341
diplomatic communications.
704
00:36:45,341 --> 00:36:47,032
[telegraph beeping]
705
00:36:47,032 --> 00:36:48,723
- Blinker Hall had to work out
706
00:36:48,723 --> 00:36:51,381
how to deliver this information,
707
00:36:51,381 --> 00:36:53,728
covering up what he
needed to cover up,
708
00:36:53,728 --> 00:36:55,972
but exposing what
he needed to expose.
709
00:36:56,904 --> 00:36:59,907
[suspenseful music]
710
00:36:59,907 --> 00:37:03,082
- [Narrator] Three
weeks after intercepting
711
00:37:03,082 --> 00:37:07,225
and decoding the telegram's
incendiary contents,
712
00:37:07,225 --> 00:37:08,536
Blinker Hall comes up
713
00:37:08,536 --> 00:37:10,952
with a brilliant
solution to the problem.
714
00:37:12,368 --> 00:37:13,852
It's complex,
715
00:37:13,852 --> 00:37:16,751
but it could provide
the perfect cover story,
716
00:37:17,683 --> 00:37:19,927
if he can pull it off.
717
00:37:21,411 --> 00:37:24,034
The Zimmermann
telegram left Berlin
718
00:37:24,034 --> 00:37:26,071
and was sent onto Copenhagen,
719
00:37:26,071 --> 00:37:29,764
then Britain by overland
and underwater cables.
720
00:37:29,764 --> 00:37:32,767
[telegraph beeping]
721
00:37:34,907 --> 00:37:36,599
It then reached Washington D.C.
722
00:37:36,599 --> 00:37:41,051
via transatlantic
cable, but crucially,
723
00:37:41,051 --> 00:37:44,054
it would've been relayed
from Washington D.C.
724
00:37:44,054 --> 00:37:49,059
to a telegram station in Mexico
city via a separate cable,
725
00:37:50,475 --> 00:37:54,306
and that means a second copy
of the message must exist.
726
00:37:56,791 --> 00:38:00,070
If it does, it will be a
version of the telegram
727
00:38:00,070 --> 00:38:01,555
that couldn't have
been picked up
728
00:38:01,555 --> 00:38:03,522
by British telegram operators
729
00:38:03,522 --> 00:38:06,318
illegally tapping
the US cable lines.
730
00:38:08,009 --> 00:38:12,462
- If they can get hold
of that second message,
731
00:38:12,462 --> 00:38:14,947
that would be much more useful,
732
00:38:14,947 --> 00:38:18,537
at least in terms of publicly
revealing how they got it.
733
00:38:20,367 --> 00:38:21,816
- [Narrator] In Mexico,
734
00:38:21,816 --> 00:38:25,199
a British agent
known only as Mr. H,
735
00:38:25,199 --> 00:38:28,927
is tasked with locating
the relay telegram.
736
00:38:28,927 --> 00:38:30,411
- It turns out that
the interception
737
00:38:30,411 --> 00:38:33,034
of the second message
is much easier.
738
00:38:35,278 --> 00:38:38,039
They do it the old-fashioned
way using money.
739
00:38:39,178 --> 00:38:41,491
- By bribing some
post office officials,
740
00:38:41,491 --> 00:38:44,977
they managed to get this
original second cable.
741
00:38:44,977 --> 00:38:47,359
- [Narrator] Blinker
Hall's inspired plan
742
00:38:47,359 --> 00:38:49,119
has worked to perfection,
743
00:38:50,328 --> 00:38:52,330
but he's about to be
thrown a curve ball
744
00:38:52,330 --> 00:38:55,367
that no one in Room
40 is expecting.
745
00:38:55,367 --> 00:38:58,059
[telegraph beeping]
746
00:38:58,059 --> 00:39:00,545
[dramatic music]
747
00:39:00,545 --> 00:39:03,893
Within 48 hours of
the Mexican operation,
748
00:39:03,893 --> 00:39:07,621
Blinker Hall has two copies
of the Zimmermann telegram,
749
00:39:09,070 --> 00:39:12,453
but it's immediately clear
to the Room 40 codebreakers
750
00:39:12,453 --> 00:39:14,041
that the new Mexican copy
751
00:39:14,041 --> 00:39:18,183
is not identical to the
original intercepted message.
752
00:39:20,634 --> 00:39:24,534
- It turns out that that second
cable was an earlier code.
753
00:39:24,534 --> 00:39:27,710
- So, now we have
another decryption task.
754
00:39:27,710 --> 00:39:29,919
[suspenseful music]
755
00:39:29,919 --> 00:39:33,060
- [Narrator] Once again,
luck is on their side.
756
00:39:34,682 --> 00:39:36,857
As with the first telegram,
757
00:39:36,857 --> 00:39:38,755
a string of numbers at the start
758
00:39:38,755 --> 00:39:41,517
of the Mexican message
provides a clue.
759
00:39:42,828 --> 00:39:47,626
The number 13042 tells
the receiver which code
760
00:39:47,626 --> 00:39:50,802
has been used to
encrypt the message.
761
00:39:50,802 --> 00:39:52,942
[suspenseful music]
762
00:39:52,942 --> 00:39:54,875
This code is a close relation
763
00:39:54,875 --> 00:39:57,015
to an earlier diplomatic cipher
764
00:39:57,015 --> 00:40:00,915
that Nigel de Grey and his team
are not only familiar with,
765
00:40:00,915 --> 00:40:04,160
they've already cracked it.
766
00:40:04,160 --> 00:40:06,542
[dramatic music]
767
00:40:06,542 --> 00:40:07,784
- So, rather fantastically,
768
00:40:07,784 --> 00:40:10,166
the British can now
read the entire message,
769
00:40:10,166 --> 00:40:11,409
not just patches of it.
770
00:40:12,962 --> 00:40:15,205
- [Narrator] Within
a matter of hours,
771
00:40:15,205 --> 00:40:18,795
the team has unscrambled
the full explosive contents
772
00:40:18,795 --> 00:40:22,489
of Zimmermann's message to the
German ambassador in Mexico.
773
00:40:24,456 --> 00:40:28,115
Even better, it confirms
the codebreaker's decryption
774
00:40:28,115 --> 00:40:30,428
of the original message.
775
00:40:30,428 --> 00:40:33,051
[telegraph beeping]
776
00:40:33,051 --> 00:40:35,571
First, the U-boat offensive
in the north Atlantic.
777
00:40:37,055 --> 00:40:39,851
- [Codebreaker] The intent to
begin on the 1st of February
778
00:40:39,851 --> 00:40:42,336
unrestricted submarine warfare.
779
00:40:43,233 --> 00:40:45,235
- The second message confirms
780
00:40:45,235 --> 00:40:47,445
everything they have
from the first message.
781
00:40:47,445 --> 00:40:50,758
This is an explosive
piece of intelligence.
782
00:40:51,932 --> 00:40:54,037
- [Narrator] Then,
as already suspected,
783
00:40:54,037 --> 00:40:57,282
Zimmermann's plan is to
forge a military alliance
784
00:40:57,282 --> 00:41:00,043
with Mexico to keep
America's focus
785
00:41:00,043 --> 00:41:02,632
on home soil, not Europe.
786
00:41:02,632 --> 00:41:06,567
[gunfire blasting]
[explosion rumbles]
787
00:41:06,567 --> 00:41:10,053
- [Codebreaker] We make war
together, make peace together.
788
00:41:11,192 --> 00:41:13,712
Mexico is to reconquer
the lost territory
789
00:41:13,712 --> 00:41:17,371
in Texas, New
Mexico, and Arizona.
790
00:41:18,717 --> 00:41:20,236
- You even get a
little extra from it,
791
00:41:20,236 --> 00:41:22,721
which is an invitation
to the Mexican president
792
00:41:22,721 --> 00:41:27,485
to encourage the Japanese
to also join the war
793
00:41:27,485 --> 00:41:29,694
on the side of the
central powers.
794
00:41:29,694 --> 00:41:30,902
[dramatic music]
795
00:41:30,902 --> 00:41:32,490
- [Codebreaker]
Signed, Zimmermann.
796
00:41:34,146 --> 00:41:38,772
- Room 40 has found the very
piece of evidence that it needs
797
00:41:38,772 --> 00:41:41,222
to lead the United
States of America
798
00:41:41,222 --> 00:41:43,604
into war against Germany.
799
00:41:46,020 --> 00:41:48,540
- [Narrator] Blinker
Hall's plan has worked.
800
00:41:49,852 --> 00:41:52,889
The new fully deciphered
version of the telegram
801
00:41:52,889 --> 00:41:55,167
leaves nothing to
the imagination
802
00:41:55,167 --> 00:41:59,275
about Germany's planned acts
of aggression against America
803
00:42:01,035 --> 00:42:02,934
and even better,
804
00:42:02,934 --> 00:42:06,489
British intelligence now
has a cast iron cover story
805
00:42:06,489 --> 00:42:09,423
for how the top secret
information was gathered.
806
00:42:10,493 --> 00:42:11,943
[suspenseful music]
807
00:42:11,943 --> 00:42:14,532
- This is really the perfect
outcome for the British.
808
00:42:14,532 --> 00:42:16,948
They can use this essential
piece of intelligence
809
00:42:16,948 --> 00:42:18,225
the way they wanted to use it,
810
00:42:18,225 --> 00:42:20,261
but they can do it
without revealing
811
00:42:20,261 --> 00:42:22,436
that they've broken
this German code
812
00:42:22,436 --> 00:42:24,714
without revealing that
they've been spying
813
00:42:24,714 --> 00:42:27,441
on the United States
for years already.
814
00:42:29,892 --> 00:42:33,378
- [Narrator] On
February 24th, 1917,
815
00:42:33,378 --> 00:42:37,037
four weeks after the original
message was intercepted,
816
00:42:37,037 --> 00:42:40,074
the copy of the telegram
sourced from Mexico
817
00:42:40,074 --> 00:42:42,249
is presented to
President Wilson.
818
00:42:43,457 --> 00:42:47,668
- Wilson's reaction to
this explosive telegram
819
00:42:47,668 --> 00:42:49,981
that threatens a
war with Mexico,
820
00:42:49,981 --> 00:42:54,123
that threatens to bring
in Japan is outrage.
821
00:42:55,331 --> 00:42:58,161
- "Oh Lord," he says,
and he knows immediately
822
00:42:58,161 --> 00:43:00,785
that American neutrality
can be no more.
823
00:43:00,785 --> 00:43:03,753
They cannot accept
a planned invasion
824
00:43:03,753 --> 00:43:06,480
or attack on American territory.
825
00:43:06,480 --> 00:43:08,206
[dramatic music]
826
00:43:08,206 --> 00:43:09,897
- [Narrator] Four days later,
827
00:43:09,897 --> 00:43:13,763
the Zimmermann telegram is
published in the American press.
828
00:43:16,076 --> 00:43:19,113
US intelligence is
credited with intercepting
829
00:43:19,113 --> 00:43:21,944
and deciphering the
scandalous message,
830
00:43:21,944 --> 00:43:25,775
keeping attention away from
Blinker Hall's very British team
831
00:43:25,775 --> 00:43:27,881
of codebreakers in Room 40.
832
00:43:29,952 --> 00:43:31,988
- This telegram is
particularly startling
833
00:43:33,472 --> 00:43:36,855
because it brings the war
home to their own borders,
834
00:43:36,855 --> 00:43:40,514
a border with a
nation such as Mexico,
835
00:43:40,514 --> 00:43:42,378
who they already
have conflict with.
836
00:43:43,551 --> 00:43:47,659
It makes Americans feel
that they're not safe.
837
00:43:47,659 --> 00:43:50,386
[dramatic music]
838
00:43:52,077 --> 00:43:53,216
- [Narrator] Incredibly,
839
00:43:53,216 --> 00:43:56,323
the telegram's contents
are so shocking
840
00:43:56,323 --> 00:43:59,533
that doubt begins to surface
about its authenticity.
841
00:44:00,638 --> 00:44:02,329
- Although the
Americans have said
842
00:44:02,329 --> 00:44:04,711
that it was American
intelligence that
found this telegram,
843
00:44:04,711 --> 00:44:07,783
there is still a number
of suspicions around it.
844
00:44:07,783 --> 00:44:10,164
- [Narrator] Proof that
the information is correct
845
00:44:10,164 --> 00:44:13,443
comes from an unlikely source.
846
00:44:13,443 --> 00:44:16,274
- Zimmermann himself
puts his hand up
847
00:44:16,274 --> 00:44:19,691
and admits that he
wrote this telegram,
848
00:44:19,691 --> 00:44:22,487
so authenticity is certified.
849
00:44:25,904 --> 00:44:27,665
- The American public react
850
00:44:27,665 --> 00:44:30,840
with utter shock
at this revelation.
851
00:44:32,324 --> 00:44:33,843
- [Narrator] In Washington,
852
00:44:33,843 --> 00:44:37,502
President Wilson knows there's
no ignoring this information.
853
00:44:38,641 --> 00:44:41,402
[dramatic music]
854
00:44:41,402 --> 00:44:45,406
As well as the threat of a
German backed war with Mexico,
855
00:44:45,406 --> 00:44:48,237
he's also now facing
the stark reality
856
00:44:48,237 --> 00:44:50,308
of the increased
U-boat aggression
857
00:44:50,308 --> 00:44:53,449
he had previously
chosen to ignore.
858
00:44:53,449 --> 00:44:55,831
[explosion rumbles]
859
00:44:55,831 --> 00:44:57,315
- In March, 1917,
860
00:44:57,315 --> 00:45:00,145
the gloves have really
come off in the Atlantic.
861
00:45:00,145 --> 00:45:03,839
The Germans are now torpedoing
any ship that they suspect
862
00:45:03,839 --> 00:45:07,152
are carrying war
material of any sort.
863
00:45:07,152 --> 00:45:10,638
At this point, Wilson
really has no choice.
864
00:45:11,639 --> 00:45:12,848
He has to act decisively.
865
00:45:13,883 --> 00:45:15,816
[dramatic music]
866
00:45:15,816 --> 00:45:18,854
- On April 6th, 1917,
867
00:45:18,854 --> 00:45:21,166
three months after the
Zimmermann telegram
868
00:45:21,166 --> 00:45:22,927
was first intercepted,
869
00:45:22,927 --> 00:45:25,688
President Wilson
finally abandons
870
00:45:25,688 --> 00:45:28,726
his long held policy
of neutrality,
871
00:45:28,726 --> 00:45:33,144
and America officially
declares war on Germany.
872
00:45:33,144 --> 00:45:34,973
[dramatic music]
873
00:45:34,973 --> 00:45:37,976
- This is really the
worst possible outcome
for the Germans.
874
00:45:37,976 --> 00:45:42,705
The Americans can now release
all the safety catches,
875
00:45:42,705 --> 00:45:44,914
flood the Western
Front with material,
876
00:45:44,914 --> 00:45:48,815
and worse yet they can
bolster the depleted ranks
877
00:45:48,815 --> 00:45:52,957
of the Allied troops with
this immense pool of manpower
878
00:45:52,957 --> 00:45:54,061
that they can draw on.
879
00:45:54,924 --> 00:45:57,755
[dramatic music]
880
00:45:57,755 --> 00:45:59,549
- [Narrator] By May, 1917,
881
00:45:59,549 --> 00:46:03,553
the American expeditionary
forces have arrived in Europe.
882
00:46:06,556 --> 00:46:08,041
Within weeks,
883
00:46:08,041 --> 00:46:11,009
the war has begun to turn
in favor of the Allies.
884
00:46:13,736 --> 00:46:14,979
[explosions rumble]
885
00:46:14,979 --> 00:46:16,946
- Prior to this point,
886
00:46:16,946 --> 00:46:19,121
Germany had every
reason to believe
887
00:46:19,121 --> 00:46:23,159
they'd at least be able to
fight the Allies to a stalemate,
888
00:46:23,159 --> 00:46:25,713
but now the Americans
have come in,
889
00:46:25,713 --> 00:46:28,475
and it's a whole new ballgame.
890
00:46:28,475 --> 00:46:30,684
The German leaders and
the German generals
891
00:46:30,684 --> 00:46:32,686
were willing to
keep on fighting,
892
00:46:32,686 --> 00:46:36,794
but the Germans
themselves had had enough.
893
00:46:36,794 --> 00:46:39,141
They are not willing
to fight anymore.
894
00:46:42,592 --> 00:46:44,491
[people cheering]
895
00:46:44,491 --> 00:46:47,252
- [Narrator] On the 11th
hour, of the 11th day,
896
00:46:47,252 --> 00:46:50,462
of the 11th month of 1918,
897
00:46:50,462 --> 00:46:53,845
World War I is officially over.
898
00:46:53,845 --> 00:46:58,850
[triumphant music]
[people cheering]
899
00:47:05,063 --> 00:47:08,826
An estimated 16 million
people have been killed
900
00:47:08,826 --> 00:47:12,105
in the so-called
war to end all wars,
901
00:47:12,105 --> 00:47:14,659
and a further 21
million injured.
902
00:47:15,867 --> 00:47:18,663
[dramatic music]
903
00:47:21,252 --> 00:47:23,702
The decoding of the
Zimmermann telegram
904
00:47:23,702 --> 00:47:27,051
was a crucial turning
point in World War I,
905
00:47:27,983 --> 00:47:30,571
yet the incredible contribution
906
00:47:30,571 --> 00:47:35,576
of the former Navy captain
Sir Reginald "Blinker" Hall
907
00:47:36,750 --> 00:47:38,925
and his pioneering
team of codebreakers
908
00:47:38,925 --> 00:47:42,825
remains a closely guarded
secret for decades to come.
909
00:47:44,033 --> 00:47:45,414
- So, why don't we hear more
910
00:47:45,414 --> 00:47:48,486
about the extraordinary
efforts of Room 40
911
00:47:48,486 --> 00:47:50,868
and the key role they
played in bringing America
912
00:47:50,868 --> 00:47:55,217
into the war and thus allowing
for an Allied victory?
913
00:47:56,045 --> 00:47:57,702
[dramatic music]
914
00:47:57,702 --> 00:48:00,567
Well, secret codebreakers
are only good
915
00:48:00,567 --> 00:48:02,086
as long as you keep 'em secret.
916
00:48:03,052 --> 00:48:04,812
[suspenseful music]
917
00:48:04,812 --> 00:48:08,126
- [Narrator] After the
war, Blinker Hall retires,
918
00:48:08,126 --> 00:48:11,543
but keeps active as a lecturer
on intelligence gathering.
919
00:48:12,544 --> 00:48:15,271
Nigel de Grey stays with Room 40
920
00:48:15,271 --> 00:48:18,896
as the team is merged with the
Army's intelligence agency.
921
00:48:19,862 --> 00:48:21,484
The new outfit becomes
922
00:48:21,484 --> 00:48:24,694
the world famous Government
Code and Cipher School,
923
00:48:25,764 --> 00:48:27,870
which has moved 50 miles north
924
00:48:27,870 --> 00:48:30,908
of the Admiralty building
to Bletchley Park.
925
00:48:32,254 --> 00:48:34,635
- So we all know about Bletchley
Park and the enigma machine
926
00:48:34,635 --> 00:48:35,913
and how crucial that was
927
00:48:35,913 --> 00:48:38,398
to the Allied efforts
in the Second World War,
928
00:48:38,398 --> 00:48:42,367
but Room 40 was really
the origins of all that.
929
00:48:44,059 --> 00:48:45,474
- [Narrator] The contribution
930
00:48:45,474 --> 00:48:48,615
of Bletchley Park's
codebreakers in World War II
931
00:48:48,615 --> 00:48:50,410
can never be underestimated,
932
00:48:53,206 --> 00:48:54,759
but it may never have happened
933
00:48:54,759 --> 00:48:59,143
without the groundbreaking
work of the Room 40 team.
934
00:49:00,696 --> 00:49:02,629
- The breaking of
the Zimmermann code
935
00:49:02,629 --> 00:49:07,289
illustrates how
important cryptography
is to the war effort.
936
00:49:08,152 --> 00:49:09,601
- The Zimmermann telegram
937
00:49:09,601 --> 00:49:13,951
is probably the most influential
coded telegram message
938
00:49:13,951 --> 00:49:16,091
sent certainly in
the First World War,
939
00:49:16,091 --> 00:49:18,817
and possibly in both world wars.
940
00:49:18,817 --> 00:49:22,442
- This was one
telegram that changed
941
00:49:22,442 --> 00:49:24,996
not just the course of the war,
942
00:49:24,996 --> 00:49:27,447
but the entire course
of modern history.
943
00:49:28,551 --> 00:49:31,313
[dramatic music]
74661
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