All language subtitles for Unsinkable.Japans.Lost.Battleship.2020.1080p.WEBRip.x265-RARBG2_English

(dramatic music)
(plane engine roars)

(gunfire popping)
(water splashes)

- [Narrator] The outcome of
World War II is at stake.

Over 400 American and Japanese warships

do battle at Leyte Gulf.

- It was the largest
naval action in history.

(light music)

- [Narrator] Japan is
counting on a secret weapon

the Americans know almost nothing about,

except her name, Musashi.

- You'll find, in the summer of 1944,

the naval intelligence experts groping

for an understanding of these huge ships.

- [Narrator] At 72,000 tons,

she's the largest battleship ever built.

- She's not just 10% bigger than some

of these other vessels,
she's nearly double.

- [Narrator] Bristling with
anti-aircraft batteries

and massive 18-inch guns.

(guns banging)

- You can't believe all the firepower

that comes up at one time.

- [Narrator] Her builders
boast, "She's unsinkable."

Yet, in her first major fight,

this super battleship is sent
crashing to the ocean floor.

(water splashing)
(metal creaks)

But mysteries have always
surrounded Musashi.

(dramatic music)

Now, Americans and Japanese researchers

are joining forces to unlock
her most stubborn secrets.

(graphics whirring)

(Hirotada speaks in foreign language)

- [Interpreter] This front part

is where flooding is taking place.

- [Narrator] Why did an
unsinkable giant go down so fast?

Was it overwhelming American air power

or a fatal design flaw that sent

nearly 1,000 Japanese
sailors to their death?

(Masahiro speaks in foreign language)

- [Interpreter] Hundreds of
people are crying for help

in horrified voices as they
were all sucked into the waves.

(plane engine roars)

- [Narrator] To unravel
the mysteries of Musashi,

the missing giant must first be found.

(water gurgling)

(waves splash)

(light music)

In February 2011, a research vessel

begins a three week expedition

in the Sibuyan Sea of
the Central Philippines.

- You know, if this was anywhere else,

all the coastline would have been changed

with buildings and high-rises
and all sorts of things.

And that's not the case here,
so we know we're looking at

basically what the pilots

saw 70 odd years ago.
(flash bulb popping)

- [Narrator] The expedition
is the brainchild

of the late Paul Allen,
co-founder of Microsoft.

The son of a World War II veteran,

Allen committed significant resources

to searching for the war's
most iconic missing shipwrecks.

Among them, the mysterious Musashi.

(ship crew chattering)

Rob Kraft is in charge of
conducting all sub sea operations.

(guns bang)

- Musashi was the pride
of the Japanese fleet.

It was so important to the Japanese people

that they didn't even
inform the population

that it has sunk.

- Lots of people would
like to find the Musashi.

It's one of the great battleships,

it's one of the truly remarkable ones

that haven't been found.

That is--
- I think there's something--

- [Narrator] David
Mearns has made a career

out of hunting for lost shipwrecks.

(soft dramatic music)

After months spent combing

through military archives
in the US and Japan--

- [David] And what it's showing you here.

- [Narrator] He's identified
the critical clues

he hopes will lead them to Musashi.

- The key is that one.

- [Narrator] One is visual,

(flash bulb pops)

aerial photographs
taken by American pilots

during their final devastating attack.

(flash bulb pops)

- [David] There's the
plane coming in lining up

right there to attack Musashi

and this is the next
frame in the sequence.

You can no longer see the
plane, but we see a torpedo hit.

(flash bulb pops)

- [Narrator] Clearly
recognizable in the background

of these photographs, is the outline

of Sibuyan Island a
few miles to the south.

- [Rob] Outside this circle?

- [David] Outside the blue circle.

- [Rob] Outside the blue.

- [David] Yeah, yeah.

- [Narrator] But there are other clues

that may narrow down
the search even further.

- And the most important one came

from one of the destroyers,
the Japanese destroyer

that was ordered to stand by Musashi.

Kiyoshimo actually took a
position for Musashi sinking.

- [Narrator] Using the position reported

by the destroyer, Kiyoshimo,

Mearns and Kraft have determined

a high-probability search area.

The tool selected for the search

is called a multibeam echosounder.

It's a type of sonar that's
mounted on a ship's hull.

An array of downward-looking
beams emitting sound waves

sweeps across the seabed

to create an image of a mile-wide swath.

(soft dramatic music)
(water gurgling)

- We're over here on the
western side of our box.

We're running the first line to the east

and this happens to be line number 13.

And each line should
take about four hours.

- And because we're looking for,

in the terms of the depth of the water,

quite a small target.

We're mapping the seabed
in very, very high detail.

So the byproduct of our search
is a really detailed map

of this particular part
of the Philippines.

- [Narrator] Even though Musashi is as big

as a 75-story building, the
battleship will only show up

as a small speck on this
vast and unexplored seafloor.

There's no guarantee she can be found.

- It all depends on her
orientation on the bottom,

if she's in one piece,
two piece, three pieces.

We should be able to
detect that and see them

in what they call the backscatter imagery.

When you hit something hard,

it shows up as a very, very dark object.

(soft music)

- [Narrator] It takes four days

to cover the high-probability area.

It yields an impressive
picture of the seabed below,

including a newly discovered seamount.

But so far, there's no sign of Musashi.

- So our highest probability to begin with

was all on the basis of this
Japanese destroyer, Kiyoshimo,

which gave a precise sinking position.

It's now very clear that

that position wasn't as
accurate as I had hoped.

And the cost of that, we're now
having to expand the search.

(soft dramatic music)

- [Narrator] Their focus
shifts to the second,

albeit less precise clue--

- That's the bow.

- [Narrator] The aerial photographs taken

by the American planes attacking Musashi.

- I mean, I think if we go down here,

we're gonna be able
to, we're gonna be able

to get a better feel.

- [Rob] Yeah.

- [Narrator] This cardboard box,

which has the same field of view

as the camera the airmen used,

allows Mearns to get a close
approximation of what they saw.

- Musashi would be about
two kilometers closer

to the island from here when
these photographs were taken.

(flash bulb pops)

And she sinks four hours later.

- [Narrator] With the evidence
gleaned from the photos,

they plot a new series of sonar runs.

- That's what we've covered,
that red line there.

Anywhere outside of that, she could be.

- I would almost bias
it further to the west,

because in that photograph,

(flash bulb pops)

she's clearly heading westerly

as opposed to north.
(flash bulb pops)

- [Narrator] But the clock is ticking.

(flash bulb pops)

The expedition only has two weeks left

to find the mystery ship.

(soft dramatic music)

Musashi was first conceived in the 1930s,

(gun popping)

a time when Japan's efforts
to expand it's territory

and influence in Asia and the Pacific

were increasingly blocked
by it's former ally,

the United States.

- Japanese national prestige
had been dealt an insult

by the Washington Naval Treaty.

Just to put it in numbers,

the treaty created circumstances where

for every 100 United States
warships that are built,

the Japanese are permitted 60.

It created a future in which
the Japanese Imperial Navy

was going to be numerically inferior

to the United States Navy.

- [Narrator] In response,
a powerful faction

begins advocating for
a different strategy.

(Toshiya speaks in foreign language)

- [Interpreter] Japan, at the time,

had neither the resources nor the budget

to build a large number of battleships

to fight against the US.

So they decided to counter
quantity with quality.

That was the idea they came up with.

- [Narrator] Quality meant
constructing giant battleships

that could overcome the
enemy's larger numbers.

The new battleship was
called the Yamato-class

after it's prototype.

To win public support, this
navy handbook likens it

to a powerful figure in a
popular movie of the time.

(sinister music)

(crowd screaming)

The Hollywood film about a
giant ape creating mayhem

in New York was a huge hit
with Japanese audiences.

(woman screaming)

- And so the comparison
is not just a comparison

evocative of power and strength,

it's also kind of pointed
squarely at New York City,

and, therefore, pointed
directly at the Americans.

(soft music)
(film whirs)

- [Narrator] In March 1938,
construction of Musashi

began here at the Mitsubishi
Shipyard in Nagasaki.

Incredibly, the giant
gantry crane that built her

is still in use today.

- The Japanese virtually had to reinvent

naval architecture and design of ships

to be able to build such colossal vessels.

- [Narrator] Work proceeded
under a literal veil of secrecy.

- When they were being built,
they were actually built

behind gigantic curtains

that were raised up in the shipyards.

And so even friendly people couldn't see

what was going on behind there.

So there was some attempt
to keep it a secret.

- A schoolgirl at the time,

Ms. Matsuura remember what it was like.

(Sachie speaks in foreign language)

- [Interpreter] I was told never to look

in the direction of the shipyard,

that soldiers are onboard keeping watch,

"You must not look or the
soldiers will take you away."

Even as a child, I kind of sensed

that a big war was going to break out.

(dramatic music)

- [Narrator] On December
7th, 1941, that war began.

In it's surprise attack on Pearl Harbor,

the Japanese Navy used
carrier-based air power

to devastating effect
against the American fleet.

Ironically, that success
only reinforced it's faith

in it's own new super battleships.

- A lot of the naval theory at the time

was based on this
fleet-on-fleet engagement.

The Japanese, in particular,
were still hoping

for that kind of thing.

This is how you arrest sea
control from the other guy,

you defeat his fleet.

(guns bang)

- [Narrator] In August 1942, Musashi began

secret sea trials.

Weapons and defenses
carefully kept out of sight

from enemy spies were put to the test.

- Mushashi's main
armament came in the form

of three turrets mounting
three Type 94 naval guns.

These were of 18-inch caliber,

and were therefore the
largest naval guns in use

anywhere in the world.

(guns banging)

- [Narrator] To defend
herself, Musashi was shielded

by the heaviest armor
ever used on a ships hull.

The high-grade steel came
from low-phosphorous iron

secretly mined in Japanese
occupied Manchuria.

For 19-year-old Masahiro Ohishi

and the hundreds of young sailors

assigned to serve aboard this giant,

Musashi was a technological wonder.

(Masahiro speaks in foreign language)

- [Interpreter] We never
thought for a second

that Musashi would sink
and people would die.

We believed that such a giant
ship could not be taken down.

(soft music)

- [Narrator] To them, she
was the King Kong of the sea.

(dramatic music)

Day 14 of the Musashi search expedition.

- Five, in this direction here.

- [Narrator] At last, the team thinks

they're onto something.

- [Man] It should be broken
in four pieces sitting there.

- [Narrator] One of their sonar runs

has revealed a promising target.

- [David] That is exactly
what you wanna look for,

bow, superstructure, things
falling off the superstructure,

blah, blah, blah, central
area, engine room,

break here, explosion there, stern.

It's all gonna be right there.

And if it capsized, it's gonna be over.

- [Narrator] But after making
several more sonar runs,

they reluctantly reach the conclusion,

the object is too large.

- [David] You know, it's 100 meters bigger

than what we're looking
for, so it's 30% bigger.

- [Rob] I think it's definitely something

other than geology, but I
don't think it's Musashi.

(light music)

- [Narrator] After three weeks,

the expedition is out of time.

The research vessel must return to port.

But they've covered a
staggering 1,400 square miles,

an area as big as the
state of Rhode Island.

- What we now have is a
very highly accurate map

of the entire area that we want to search.

We know where she's not, we've ruled out

large swaths of the Sibuyan Sea.

- [Narrator] And their
commitment to the task

has only intensified.

- Everybody's kinda got a
lot of blood, sweat and tears

in trying to find this wreck.

You know, you get this
personal passion going

trying to find this thing.

(dramatic music)

- [Narrator] But to succeed,
they must first find

a better tool for searching
the rugged sea floor below.

(water splashing)

(dramatic music)

By the time Musashi joined
the Japanese war effort

in the Pacific in 1942, the
momentum was about to shift.

- The Japanese, actually,
are prevailing at this point,

'cause they're better at
surface warfare than we are

at this early stage in the game.

What then becomes clear

is that anytime aircraft
carriers get involved,

the whole thing changes.

- The US embraces naval airpower

in a way that it just hadn't before.

It revises the way that
it trains, revises tactics

and it revises weapons to the extent

that it introduces a new fighter,

a new dive bomber, a new torpedo bomber,

and it even introduces a new torpedo.

- [Narrator] The Mark 13
torpedo was more reliable

and could be dropped at higher altitude

than it's predecessor.

At the same time, American intelligence

secured a valuable lead.

- On the island of Tulagi,
Americans captured a document

that was a warship recognition manual

that was to be used by
Imperial Navy sailors

to recognize their own ships.

And it had a drawing
of a Yamato-class ship.

- [Narrator] But after that, nothing.

It's as if Japan's most
secret weapon had vanished.

- You'll find in the summer of 1944,

the naval intelligence experts groping

for an understanding of these huge ships

and they came up with estimates
that were just unbelievable.

- [Narrator] But as they
would later discover,

even those estimates were way too small.

(dramatic music)

By June 1944, American forces succeeded

in pushing the Japanese fleet,

totalling some 60 ships and 450 aircraft,

out of the Western Pacific.

The battle became known as the
Great Marianas Turkey Shoot.

- They call it that because they harvest

so many Japanese aircraft.

They shoot them down wholesale.

The Japanese lose half
their carrier strength

and they lose almost all
of their naval aviation.

- [Narrator] American
general Douglas MacArthur

was now poised to invade the gateway

to Japan itself, the Philippines.

On October 20th, MacArthur came ashore

on the eastern side of Leyte Island,

where American troops
encountered little resistance.

- The opinion, united, of
American intelligence agencies

was that the Japanese
Navy would not come out.

We based our ideas on the assumption

that the Japanese would need
a considerable amount of time

to train new aircrew and pilots

for their aircraft carrier groups.

- [Narrator] But American
intelligence was ignoring

one critical fact: Japan's
Navy remained committed

to fighting a decisive battle at sea.

It's surface fleet was
still largely intact,

led by two giants Americans
had yet to lay eyes on,

Musashi and Yamato.

- American radio
intelligence had knowledge

of the movements of these Japanese ships,

but still not of their characteristics.

- [Narrator] On October 24th, 1944,

Admiral Kurita's Center
Force, with 26 ships,

entered the Sibuyan Sea.

Two other slightly smaller Japanese fleets

approached from the south and north.

The Battle of Leyte
Gulf was about to begin.

(soft dramatic music)

- In the morning, when Kurita
is crossing the Sibuyan Sea,

the reconnaissance flights picked this up,

and, of course, at that
point, they're aware

they got two very large
battleships down here.

- [Narrator] American
Pilots were the first

to catch a real glimpse
of Musashi and Yamato.

- We knew that they had
two big battleships,

and that's about all we knew.

And it was, obviously, the
biggest thing we'd ever seen.

- [Narrator] Although caught by surprise,

the US Navy was prepared.

7th Fleet moved to guard the
Leyte landing site itself,

while 3rd Fleet deployed in
three groups to the north.

- Unfortunately, the one
element of the 3rd Fleet

that's closest to San Bernardino Strait

is a little bit weaker because it sent

one of it's carriers off to refuel.

It's sole remaining large
carrier was only half the size

of the two giants bearing down on it

with 24 more warships
in Japan's Center Force.

(soft dramatic music)

(man speaking faintly on radio)

- [Narrator] In late February 2015,

Rob Kraft and David Mearns
renew their search for Musashi.

Since they were last here,

they've found the perfect tool
for the difficult task ahead.

It's now installed aboard the
expedition yacht, Octopus,

equipped with state-of-the-art
deep sea equipment.

Their key search tool is still so new,

it's rarely been used in the deep ocean.

(machine whirs)

- AUV is an autonomous underwater vehicle.

Our AUV is capable of
diving down to 1,500 meters.

It takes with it a side scan sonar system

that looks out on the sides
and provides us an image

of things that may be
lying on he seafloor.

- [Narrator] It's survey
route is selected based on

the bathymetric map that system
engineer Wayne Szydtowski

compiled during the 2011 expedition.

- This map is of the, basically,
of the sub sea volcano

that we're seeing.

And so, using this map,

we then program the autonomous vehicle.

- [Narrator] Traveling 2/3 of a mile down

and a few hundred feet
above the ocean floor,

the AUV maps the terrain.

But distinguishing a man-made object

among the rugged volcanic
outcrops is challenging.

- Because a lava rock is as reflective

as the acoustic waves are that we use

to bounce off the metal of the Musashi.

- [Narrator] After 18 hours,
the AUV returns to the surface

and is brought onboard
to download the data.

- Everybody had a go at looking
at this HYSCAN information.

Everybody, what do you see?

Oh, that's something shiny there.

That's a rock, no that's a rock.

No, that's something.

No, that's a rock.

- [Narrator] The first
AUV survey yields nothing,

as does the second.

- And I'll tell you
that, up to that point,

we were starting to
second-guess ourselves.

We had searched a large portion
of the primary search area.

And we weren't finding
what we had hoped to find.

- [Narrator] On the third run,
they finally see something.

(water gurgling)

- Generally, when you're finding a wreck,

it's either happening instantaneously,

but, in this one, it was
a bit of a slow burner,

because there sonar image
didn't sort of shout out,

"This is Musashi, this is where I sank."

it was more of there was an
indication something was there.

- [Man] David, buoy in the water.

That's a safe heading

Better wench that one up.

- [Narrator] For a
closer look, they launch

a remotely operated vehicle, or ROV.

- It's smaller than a Volkswagen Bug,

but it's still quite substantial.

And it's on a cable as
well, but in that cable

it has power conductors and fiber,

and through that, we get to watch

our HD camera that's
on the end of a tether.

- [Narrator] It will take the ROV an hour

to reach the ocean floor
almost a mile below,

plenty of time to wonder if, at last,

they're going to set eyes on Musashi.

(dramatic music)

On the morning of October 24th, 1944,

the skies over the Sibuyan Sea were filled

with over 40 American warplanes.

- US Naval aircraft that opposed
the Japanese Center Force

in the Sibuyan Sea consists
of the Hellcat fighter,

the Helldiver dive bomber, and
the Avenger torpedo bomber.

- [Narrator] The fighters led
the way with strafing runs.

- You're gonna go after the battleships

because they are the biggest target.

They can do the most damage to you,

and, therefore, you want to take them out.

- [Narrator] But the
Japanese gunners were ready,

(plane engines roars)

unleashing a hail of fire

from Mushashi's 100 anti-aircraft guns.

(guns banging)

(Akio speaks in foreign language)

- [Interpreter] Aerial
attacks had become fierce

after war broke out.

So the decision was made

to strengthen anti-aircraft defenses,

and machine guns were also rapidly added.

But there was no industrial capacity

to manufacture bullet-proof
armor at this point.

- [Narrator] With little to protect them,

some of the gun crews
suffered heavy casualties.

(Yoshiaki speaks in foreign language)

- [Interpreter] Everything
was blown to bits.

There were pieces of
machine gun everywhere

with human flesh stuck to them.

I could not believe that they
were parts of human beings.

- [Narrator] Bob Freligh
was a 22-year-old pilot

flying an Avenger torpedo bomber that day.

- The sky is so big up there,
I don't see all the fighters.

I don't have time to look
around to see anybody else

because everything happens like that.

- [Narrator] What he did see
was a giant battleships below.

- The Musashi has 11
planes coming in on it.

You're coming down and
you start leveling off.

And all this time, they're shooting at you

and you don't know whether
this bullets gonna hit you or.

So you get about the distance
that you think you should be,

at the altitude you should
be, open your bomb bay doors,

and you're all set, boom.

(plane engine roars)

- [Narrator] His rear gunner watched

as their 2,000 pound torpedo slammed

into Mushashi's port side.

(torpedo bangs)

- The torpedo bomber is
the most effective weapon

against a battleships because
it can release something

that carries a great deal of punch.

The American Mark 13
torpedo carried a warhead

of 600 pounds of high explosive.

That was enough force to
punch through an armor belt.

(dramatic music)

- [Narrator] Musashi withstood the initial

American assault, but
the attacks kept coming.

(torpedoes banging)

- The fleets that are there at Leyte

consist of multiple aircraft carriers.

It's mind-boggling by today's standards

how many ships were there.

And so, as a result of
that, they can continue

to attack and attack, and
wave after wave coming in.

(torpedo bangs)

- [Narrator] During the
last wave, an American pilot

took his memorable series of photographs.

(flash bulb popping)

(plane engines roar)

- [Narrator] The relentless
onslaught began to take a toll.

- When the Musashi loses
speed and falls behind,

then it's obvious that she's damaged,

so now's the moment to
close in for the kill.

(soft dramatic music)

- [Narrator] Lionel
Gilbow was the rear gunner

in a Helldiver bomber.

(plane whooshes)

- I probably dived-bombed a battleship

with a 2,000 pound armor piercing bomb,

right down the stack.

(torpedo bangs)

- These particular ships
are very formidable ships,

but they also made very large targets

that were easily identified.

And I think that's one of the reasons

a lot of the aviators
concentrated on Musashi,

and she paid the price as a result.

- [Narrator] Yamato escaped the onslaught,

but at 7:39 p.m., four hours
after the final attack,

Musashi, crippled, yet
miraculously still in one piece,

rolled over and sank.

(propellers whirring)

(Masahiro speaks in foreign language)

- [Interpreter] Hundreds of
people are crying for help

in horrified voices, as they
were all sucked into the waves.

(water splashing)

(metal creaks)

(soft music)

- [Narrator] In the pitch
darkness of the deep sea,

the ROV pilot carefully
maneuvers his vehicle.

- We came across some very
small pieces of debris

which looked the right age,
looked the right material.

But we weren't quite certain.

- Everybody was pretty
much running on adrenalin

at that time.

It was very exciting.

- [Narrator] The ROV moves slowly

through this unfamiliar landscape.

- It took about, I guess,
a half hour or 45 minutes

before we started getting
into the heavier debris.

And then it became more and more obvious.

- [Man] Look, you see them, right?

There's three characters
over there, I think.

- [Man] That's Japanese,
it's a Japanese warship.

- The minute we found the valve

that had the Kanji writing
on it, it was like,

okay, this is Japanese,
now all we have to do

is prove that it's Musashi.

- [Narrator] To do that, they
need to find the ship's bow.

- [Man] There's the
bollards, two bollards.

So we're not too far away.

It'll be above the degaussing cable.

Something's there.

It's there.

- [Narrator] The gold paint is gone,

but the outline of the
imperial Japanese flower emblem

is still there.

- As soon as we found the
chrysanthemum on the bow,

we knew what we were looking at.

- That's, that's proof positive.

- It wasn't the kind of
jumping up and shouting for joy

that I've experienced in the past,

it was a sort of a quiet relief.

We had finally done it.

- [Narrator] At long
last, Musashi is found,

but a new, and still
more intriguing mystery

is about to emerge.

(soft music)

Over the next week, the
search team explores the wreck

of the super battleship.

- There's some shells on the top

- [Rob] I think there's another one

of the mounts for a light, or a--

- [Narrator] 70 years
after she disappeared,

they're compiling the
first detailed picture

of a lost technological marvel.

- Because there are no
drawings for this ship

and there's only a handful of photographs,

so we're the first people really

to document what she looks like.

- [Narrator] They also find
signs of those who sailed her,

a shoe, a helmet,

and something unexpected on a warship.

- [David] That's film.

- [Woman] No, that's film.

- [David] That is a film strip.

It's not just a metal ship, these are crew

that served in it,

and some obviously died
on the site as well,

so it's important to document that.

(soft dramatic music)

- [Narrator] Musashi lies a good distance

from the sinking position reported

by the destroyer Kiyoshimo.

(flash bulb pops)

But that's not the only reason
she was so hard to find.

- The Musashi is literally
on the side of a volcano.

And if you've hiked up a volcano before,

you'd know there's great big
huge rocks and outcroppings

and boulders, and so it's
hidden inside the geology.

- [Narrator] The difficulty
in finding the wreck

is also explained by
her shocking condition.

- Just the complete and utter destruction

of the ship itself, the
stern and the bow sections

are really the only whole
parts of the hull that remain.

The bridge is somewhat
intact from what we can see,

but the rest, you know, the
center section of the ship

was just completely destroyed.

- So, essentially, it's broken it's back

in at least two different locations.

And for a ship that
withstood so many attacks

from torpedoes and bombs
and essentially sank intact,

that's more than I expected.

- [Narrator] What then could have caused

such widespread destruction?

(graphics whirring)

It's a question which,
so far, has no answer.

(dramatic music)

(guns bang)

One of the last pieces to be discovered

is Musashi's most potent weapon.

(guns banging)

- Which is, obviously, what
caught everybody's imagination,

these special 18-inch guns.

These guns are held into
the body of the ship,

into the barbettes by gravity alone.

So when the ship capsizes,
they're incredibly heavy objects

that just fall out under their own weight.

We found one of these guns
after a week of searching.

- [Narrator] By now, the
expedition has assembled

an extensive record of Musashi,

over 100 hours of video footage alone.

- We want to make sure that
we have fully documented

the condition and the state of the wreck

so we can share that with
everybody and, you know,

what we've done here and the
data that we've gathered.

We'll provide the clues
that people can use

to recreate or have an understanding

of what actually happened.

(light music)

- [Narrator] The search
team has opened a door.

Now, others must step in to
unravel Musashi's final hours.

In March 2016, a group of
Japanese experts assembles

in Tokyo to take up the challenge.

(soft dramatic music)

To help them, the
Japanese broadcaster, NHK,

has created a valuable tool.

Like pieces of a gigantic
puzzle, it's taken the hours

of digital images gathered
by the search expedition,

painstakingly piecing them back together,

and creating a unique
3D model of the wreck.

(graphics whirring)

Only now is Musashi's
enormous size apparent.

At 263 meters, some 900 feet,

she's longer than three jumbo jets.

(men speaking in foreign language)

To begin with, these
experts want to find out

why a ship so many believed unsinkable

should fail it's first serious test.

(Masami speaks in foreign language)

(man speaks in foreign language)

- [Interpreter] What is that
thing that looks like a hole?

- [Narrator] Masami Tezuka
has been studying the Musashi

for 30 years.

He believes he's identified one clue,

a damaged section protruding
from the port bow,

most likely caused by a torpedo strike.

(Masami speaks in foreign language)

- [Interpreter] Musashi
would lose speed as a result,

making it difficult to steer her.

From an attackers point of view,

a battleship that's dragging
swuld have been easier to hit

with bombs or torpedoes.

- [Narrator] The last photo of Musashi

shows her down at the
bow, leading to the belief

that flooding here caused her to sink.

But a new scientific investigation

at the University of Kobe
tells a different story.

Professor Hirotada Hashimoto, a specialist

in naval architecture,
conducted the analysis.

When he simulates flooding inside the bow,

the ship does pitch forward.

But results show, water-tight compartments

in the rest of the ship
would not have been affected.

(Hirotada speaks in foreign language)

- [Interpreter] Even if the bow,

including the part protected
by armored plating,

is completely filled with water,

the ship will still be
left with enough buoyancy.

So this flooding alone
definitely could not have caused

the ship to sink or capsize.

- [Narrator] To find
answers to why Musashi sank,

these experts will have to look elsewhere,

starting in the place where
Musashi was constructed.

(soft music)

At the Mitsubishi shipyard in Nagasaki,

the Japanese team makes
an important discovery.

A file marked Musashi is
uncovered in the company archives.

It contains more than 200 pages

of never-before released
original blueprints.

- [Narrator] By comparing
images of the scattered pieces

of the wreck with the blueprint,

the team is able to identify them.

(men speaking in foreign language)

A pump, a boiler, all parts protected

by the heavy steel armor

intended to make Musashi unsinkable.

(Akio speaks in foreign language)

- [Interpreter] So the biggest question is

where did the armor go?

- [Narrator] In the
high-resolution sonar image

of the debris field, one structure
attracts their attention.

Examining video footage from the area,

they discover a 90-foot piece of steel.

It looks like part of the missing armor.

(graphics whirring)

When they match it up to the 3D model,

they find it comes from
the hull on the port side.

But how did it come loose?

- Musashi's armor belt was so thick,

that everyone felt very
confident onboard the ship,

that they could stand up to the punishment

of any weapon that could be thrown at it.

But, whereas ships making
use of a thinner plate

that could be welded, Musashi's
armor could not be welded.

It was simply too thick.

And so they turned back
their the 19th century

and simply hot riveted
the plates together.

- [Narrator] A company that took part

in riveting the armor for Musashi

is still operating in Osaka.

Two workers recreate the
technique used at the time

to join these two pieces of armored plate.

(dramatic music)

(machine banging)

A special hammer drives
the rivet into place.

(soft music)

- Japanese sailors assigned to Musashi

had great confidence in the ship.

They thought it was
unsinkable, and that's because,

above deck, they saw nothing
but guns and firepower.

But then below deck, they were aware

that the ship had the thickest armor

of any warship in the world.

- [Narrator] But the
Japanese investigation team

doesn't share the sailors' confidence.

(Hayao speaks in foreign language)

- [Interpreter] I think
rivets were the problem.

No matter how thick the armor plates were,

they wouldn't last once
the rivets came loose.

- [Narrator] Musashi's armor was attached

at a slanting angle to
deflect incoming shells.

(man speaks in foreign language)

- [Interpreter] She was built
to withstand artillery duels

against other battleships.

But, instead, she was hit by
torpedoes and aerial bombs,

which weren't weapons she expected to face

when she was designed.

(guns popping)

- [Narrator] If a torpedo
from an attacking aircraft

struck a a joint in the armor plate,

it could cause rivets to fail and seawater

to begin to seep in.

(plane engine roaring)

So how did this apparent vulnerability

to torpedo strikes go unnoticed?

(guns banging)

(light music)

(men speaking in foreign language)

The team discovers early concerns

about this possible design flaw.

A former officer on Musashi,

who earlier served on
her sister ship, Yamato,

made this recording before he died.

(Haruo speaks in foreign language)

- [Interpreter] I heard from Yamato's crew

that during a torpedo attack,

although the armor remained intact,

the rivets were blown off,

and, gradually, water started
to leak in around the joints.

It made me realize, if we were
hit by a lot of torpedoes,

there would be more flooding,

and that could be her weakest point.

- [Narrator] Shigeru
Makino, a naval designer

who oversaw the construction of Musashi,

reported similar
misgivings, but later wrote,

"The naval authorities decided

"to simply patch the armor joint

"rather than find a permanent
solution to the problem."

In the minds of Musashi's 2,400 crewmen,

many still in their teens or early 20s,

the Imperial Japanese Navy
instilled a beguiling illusion,

their super battleship was
quite simply unsinkable.

(soft music)

One of them, Masahiro Ohishi,
believed it to the very end.

(Masahiro speaks in foreign language)

- [Interpreter] Right up
till the moment it sank,

I didn't think it could happen.

The Musashi wouldn't even budge an inch

with a torpedo or two striking her.

There would be no
flooding, so we were told.

- [Narrator] Musashi
also proved vulnerable

to another unanticipated weapon,

armor-piercing bombs from the air,

as the search team discovered.

- [Man] See that's an issue.

- [Rob] Yeah, once you get
in there a little tighter--

- [Narrator] Underwater footage revealed

one of several 3-foot holes
rupturing the ships deck.

- In a short section of the bow,

we saw the damage from the bombs.

So that's corroborating what
the US pilots were telling us

about the hits they
were getting on Musashi.

- These weapons, although they
are as crude and as simple

as they can be, sent
through the air column,

penetrate decks and
can explode below deck.

This, in the end, causes
great destruction on Musashi.

(soft dramatic music)

- [Narrator] Now, thanks to
the 3D model of the wreck,

the full extent of that
destruction can be seen,

especially up on the
bridge, where the captain

and many of officers were stationed.

A gaping 20-foot hole gouged
into the starboard side

marks where a bomb struck.

One crew member up here
miraculously survived.

Kenji Otsuka remembers what happened.

(Kenji speaks in foreign language)

- [Interpreter] All the
desks, chairs, everything,

flew to the port side.

Bodies of those who were killed
were piled up there, too.

The blast wave knocked
us over, killing some.

One man lost everything from his neck up,

sitting in a chair about 10-feet

from where I was, just dead.

- [Narrator] Standing on
an open observation deck,

Captain Inoguchi suffered a
shrapnel wound in the shoulder.

Protected from the fire himself,

crewman Kotaki observed what happened.

(Tatsuo speaks in foreign language)

- [Interpreter] I saw him from behind.

He was covering his shoulder
with his hand like this,

holding binoculars like
this, and giving commands.

Any ordinary person would have
collapsed from such injuries.

I thought, "That's a true commander."

- [Narrator] Like her brave captain,

Musashi sustained multiple hits

from weapons she was
never designed to face.

Incredibly, her unusual
strength allowed her

to go down in one piece,
leaving one final question,

what tore her to pieces as she sank?

(water splashing)

(dramatic music)

- [David] That's a 46-centimeter shell

underneath there, right?

- [Narrator] When the search team

originally discovered Musashi--

- The turret housing was blown away.

- [Narrator] They couldn't
believe the wreckage

was spread over such a wide area,

a square kilometer, more
than half a square mile.

- Most of the shipwrecks that I've done

are in deeper water than this,

and we're seeing debris fields
of 300 meters, 400 meters.

So to see one twice or
three times that size

is really telling me that not only

are we dealing with a large ship,

but a large ship that
has been blown apart.

(man speaks in foreign language)

- [Narrator] How does a ship
that left the surface intact

now lie shattered over the ocean floor?

The Japanese team is
determined to find an answer

to this final mystery of Musashi.

(man speaks in foreign language)

- [Interpreter] I'm not sure
if it came from a boiler

or something else, but is it possible

this damage was caused by steam exploding?

- [Narrator] One member doesn't think so.

Masatake Yoshida has
been studying explosives

for over 30 years.

He believes something
else tore Musashi apart.

(Masatake speak in foreign language)

- [Interpreter] I can't
think of any explanation

besides a gunpowder explosion.

If an explosion like that occurred,

her internal parts would have
shattered into many pieces.

(soft music)

- [Narrator] But where did

this massive explosion take place?

One piece of debris in particular

has caught Yoshida's attention.

Although mangled almost
beyond recognition,

it's part of the magazine,
holding the shells

for one of Musashi's main guns.

(Masatake speaks in foreign language)

- [Interpreter] Thick steel like this

wouldn't have ended up
being so badly twisted

if the ship had just sunk.

- [Narrator] Since Musashi
fired her main guns

only a handful of times
during her final battle,

an estimated 160 shells
and 100 tons of gunpowder

were still stored inside her.

(soft dramatic music)

Suspicion as to where
the explosion occurred

falls on the second main gun.

- [David] So that was literally--

- [Narrator] And firsthand reports

David Mearns uncovered seem to support it.

- To see that level of
damage on the seafloor

tells me only one thing,
that the Japanese survivors

who heard explosions as it was capsizing,

those explosions were
actually magazine explosions.

- [Narrator] In the final moments,

as Musashi heeled over and sank,

a few eyewitnesses
aboard a nearby destroyer

reported seeing the flash
from a small explosion.

(Masatake speaks in foreign language)

- [Interpreter] Which
means that some fires

were already burning inside her.

That makes me think
that initial combustion

rapidly spread into an explosion.

Gunpowder contains some
oxygen, so even underwater

where there's none, under
the right conditions,

a combustive explosion can occur.

- [Narrator] To test his hypothesis,

Dr. Yoshida ran a computer simulation.

It clearly shows a ship
made of heavy steel

would have suffered catastrophic damage

from an explosion below
her second main gun.

(dramatic music)

The ships core would have splintered

into hundreds of small pieces

with only the bow and stern
remaining relatively intact.

The high-resolution sonar map confirms,

this is how the wreck
rests on the seafloor.

David Mearns believes other
factors also contributed

to the massive damage
sustained by Musashi.

(soft dramatic music)

- We see that a large section
of the bow was imploded

and we can look at the drawings and know

that there's water-tight
compartments in there,

and they've squeezed as
the ship sank very quickly.

- [Narrator] As Musashi
plummets to the bottom,

a crushing pressure, equivalent
to the weight of a car,

bears down on every square inch.

- When it hits the sea bed,
it's hitting the seabed,

actually, at very high
speed, probably a minimum

of 15 knots, maybe as much as 25 knots.

And there's impact damage.

And all of this was evident
in one section of the bow.

- [Narrator] Somewhere in
Musashi's twisted remains

lies her captain, Toshihira Inoguchi.

He went down with his ship

after handing over his final report.

In it, he wrote, "I am truly glad

"that the other battleship
suffered almost no damage,

"and I feel some consolation in thinking

"that Musashi was able to
assume the role of a victim."

(dramatic music)

(plane engines roaring)

(torpedoes banging)

- [Narrator] Musashi bore the brunt

of the American air assault
on October 24th, 1944,

(torpedoes banging)

leaving most of Japan's
Center Force unscathed,

including the super battleship, Yamato.

Undetected, Admiral Kurita

and his 20 remaining ships
steamed through the night

heading for the American
landing site at Leyte

to catch the defending force
from 7th fleet by surprise.

On October 25th, led by the
super battleship, Yamato,

(guns banging)

the Japanese Navy launched
the decisive surface attack

it had long sought.

But a bold strike by American destroyers

and destroyer escorts managed to confuse

the Japanese commander.

- And so Admiral Kurita
makes the fateful decision

to reverse course, and in so doing,

he walks away from what would have been

the most lopsided victory of
the Japanese Imperial Navy

in the Second World War.

- [Narrator] Japan's Navy had gambled

on winning the world's biggest sea battle

to bring America to the negotiating table.

But they made a fatal miscalculation.

Surface ships with big guns

were no longer the dominant force at sea.

- The age of the battleships,

the building and the loss of
the Musashi is the endpoint.

They weren't gonna be defeated
by another battleship,

another great battleship, but by aircraft.

And that's when the era of
aircraft carriers took off.

(soft dramatic music)

On October 24th, 2016, at
Yasukuni Shrine in Tokyo,

surviving crew members from Musashi

gathered to remember their lost comrades.

The discovery of the wreck
and the evidence it reveals

of Musashi's vulnerability
is a cruel reminder,

this was not the unsinkable battleships

they were led to believe her to be.

But for crewman Tsukada,

the wreck still bears
an important message.

(Yoshiaki speaks in foreign language)

- [Interpreter] I think the Musashi

would like the people to know

how bravely her crew
members fought and died.

What an astonishing battleship she was,

how she fought and met her tragic end

in the emptiness of war, I
think those are the messages

that the Musashi wants to send us.

(soft music)

- [Narrator] For Bob Freligh,
an American pilot who launched

one of the many torpedoes that sank her,

Musashi's discovery stirs
thoughts of reconciliation.

- I don't want any Japanese survivor

to think that I'm trying to
laud these medals over them.

Our opportunity is, we
have a common ground.

They are survivors of the same action

that I'm a survivor of,

and I'd just like to
say, welcome, brother.

(bell dinging)

- "At the going down with the sun,

and in the morning we will remember them."

- [All] We will remember them.

- [Narrator] Above the wreck site

in the Sibuyan Sea,
(somber horn music)

the crew of the Octopus pay
their own final respects.

- It is a war grave.

You know, we as sailors
and seafarers ourselves,

we have a lot of respect
for what happened here.

(soft music)

- [Narrator] Instead of warplanes,

they launch a flight of paper cranes,

symbol of the peace that has endured

for three-quarters of a century

between once bitter
enemies of World War II.

(soft dramatic music)