NARRATOR: HIDDEN BENEATH THE PACIFIC ISLAND OF OKINAWA ARE THE REMAINS OF ONE OF THE MOST DEADLY DEFENSIVE STRUCTURES OF THE SECOND WORLD WAR.

MAN: MORE THAN 60 MILES OF TUNNELS ON OKINAWA.

IT'S A COMPLETE HONEYCOMB.

NARRATOR: FORTIFICATIONS DESIGNED BY THE JAPANESE TO TURN THE ISLAND LANDSCAPE INTO A KILLING ZONE.

MAN: IT'S LITERALLY DEATH TRAP, DEATH TRAP, DEATH TRAP, DEATH TRAP, THAT THE AMERICANS HAVE TO ADVANCE THROUGH.

NARRATOR: CONCEALED BUNKERS... SUBTERRANEAN HEADQUARTERS... IMPENETRABLE ARTILLERY PLACEMENTS... AND A FANATICAL ARMY INTENT ON FIGHTING TO THE DEATH.

MAN: THIS STRATEGY IS GOING TO MAKE THE AMERICANS FIGHT FOR EVERY SQUARE INCH OF THIS ISLAND.

NARRATOR: THIS IS THE STORY OF THE TUNNELS OF OKINAWA.

THE BIGGEST CONSTRUCTION PROJECTS OF WORLD WAR II.

ORDERED BY HITLER AND HIS JAPANESE ALLIES TO SECURE WORLD DOMINATION.

NOW THE RUINS SURVIVE AS DARK REMINDERS OF THEIR FANATICAL MILITARY AMBITION.

THESE ARE THE SECRETS OF THE WORLD WAR II MEGA WEAPONS.

APRIL 1, 1945.

THE PACIFIC ISLAND OF OKINAWA.

24-YEAR-OLD HAJIME KONDO IS SHELTERING IN A WARREN OF TUNNELS BENEATH THE ISLAND... AS THE SHELLS OF A MASSIVE ALLIED INVASION FLEET RAIN DOWN.

[WHISPERING] The tunnel is holding.

[EXPLOSION] THEY CAN'T GET TO US DOWN HERE.

NARRATOR: HE'S ONE OF THOUSANDS OF HIDDEN JAPANESE TROOPS LYING IN WAIT FOR THE UNSUSPECTING AMERICANS.

[WHISPERING] Hey, look, they're here.

MAN AS KONDO: THEIR TANKS CAME FIRST AND THEN THE INFANTRY COMPANIES FOLLOWED.

NARRATOR: KONDO HAS BEEN ORDERED TO HOLD HIS FIRE UNTIL THE ENEMY ARE RIGHT ON TOP OF HIM.

THE FUTURE OF JAPAN WILL BE DECIDED HERE.

EVIDENCE OF THIS VAST SUBTERRANEAN LABYRINTH CAN STILL BE FOUND BENEATH THE SURFACE OF MODERN-DAY OKINAWA.

CONFLICT ARCHAEOLOGIST TONY POLLARD IS EXPLORING THE MAEDA ESCARPMENT.

A RIDGELINE THE AMERICANS WOULD DUB "HACKSAW RIDGE."

I'M JUST INSIDE THE OPENING TO A JAPANESE TUNNEL SYSTEM.

AND IT DISAPPEARS OFF BENEATH MY FEET.

BUT ALREADY I CAN SEE THE WORK THAT'S GONE INTO THIS.

THIS ALMOST SQUARED-OFF TUNNEL.

WHAT THE JAPANESE ARE DOING IS USING THE ISLAND AS A FORM OF DEFENSE.

WHAT THEY'RE HOPING IS THAT THE ISLAND'S GOING TO WIN THE BATTLE FOR THEM.

NARRATOR: THE STORY OF THE DEFENSE OF OKINAWA BEGINS IN 1942.

IMPERIAL JAPANESE FORCES HAVE SWEPT ACROSS EAST ASIA, CAPTURING VAST STRETCHES OF TERRITORY AND HUNDREDS OF ISLANDS REACHING OUT ACROSS THE PACIFIC.

BUT THEY HAVE BEEN BEATEN BACK BY AMERICAN FORCES.

BY JUNE 1944, AFTER A SERIES OF INCREASINGLY FEROCIOUS BATTLES, THE JAPANESE KNOW THEY MUST SOON MAKE A LAST STAND IF THEY'RE TO STOP THE AMERICANS INVADING JAPAN ITSELF.

[MAN SPEAKING JAPANESE] NARRATOR: AN EMERGENCY MEETING IS CALLED AT IMPERIAL HEADQUARTERS IN TOKYO.

[SPEAKING JAPANESE] NARRATOR: AMONG THOSE PRESENT IS CHIEF OPERATIONS OFFICER FOR THE 32ND ARMY, COLONEL HIROMICHI YAHARA.

SO FAR, WE HAVE DEPLOYED TOO FEW GROUND TROOPS TOO LATE.

ONE ISLAND AFTER THE OTHER.

EACH HAVE FALLEN.

WE MUST NOW SELECT AN ISLAND WE THINK THE U.S. WILL ATTACK AND DEFEND IT TO THE HILT.

MAN: YAHARA'S INTERESTING BECAUSE UNLIKE A LOT OF SENIOR STAFF OFFICERS AND JAPANESE COMMANDERS, HE'S ACTUALLY TRAVELED THE WORLD A LITTLE BIT.

HE'S SERVED ON THE STAFF COLLEGE IN THE UNITED STATES.

HE'S A REALIST, HE'S A PRAGMATIST.

YOU KNOW, THERE ARE FEW PEOPLE WHO HAVE A SLIGHTLY MORE REALISTIC VIEW OF THINGS, AND YAHARA IS DEFINITELY ONE OF THOSE.

NARRATOR: YAHARA'S GARRISON IS STATIONED 350 MILES SOUTH OF THE HOMELAND ON THE JAPANESE ISLAND OF OKINAWA.

HE BELIEVES THAT TO THE AMERICANS, IT WOULD BE THE IDEAL STAGING POST FOR ANY INVASION; THE LAST STEP BEFORE MAINLAND JAPAN.

IT'S MAKE OR BREAK.

THEY MUST HALT THE AMERICANS HERE.

REINFORCEMENTS ARE QUICKLY SENT TO BOLSTER YAHARA'S FORCES ON OKINAWA AND IMPERIAL HEADQUARTERS ISSUE CLEAR ORDERS FOR HOW THE ISLAND SHOULD BE DEFENDED.

THE ORIGINAL JAPANESE PLAN FOR OKINAWA IS, AS THE AMERICANS AND ALLIED FLEETS GET CLOSER, THEY'RE GOING TO SORTIE HUGE AIR FLOTILLAS.

THE WHOLE POINT WAS TO CATCH THE AMERICAN FLEET AT SEA AND DESTROY THEM BEFORE THEY LAND.

NARRATOR: FOR THE PLAN TO SUCCEED, OKINAWA NEEDS TO BECOME ONE MASSIVE AIR BASE.

SO, THE JAPANESE SET TO WORK BUILDING A STRING OF 6 AIRFIELDS ACROSS THE ISLAND.

TONY POLLARD HAS BEEN GRANTED SPECIAL ACCESS TO EXPLORE ONE OF THEM.

TODAY, KADENA IS A U.S. AIR FORCE BASE.

BUT IT'S STILL LITTERED WITH EVIDENCE OF ITS WARTIME JAPANESE ORIGINS.

POLLARD: THIS STRUCTURE IS REALLY INTERESTING.

IT'S A TECHNIQUE OF BUILDING IN CONCRETE THAT I'VE NOT REALLY SEEN BEFORE.

AND WHAT THEY'VE DONE HERE IS THEY'VE MOUNDED UP EARTH AND THEN POURED THE CONCRETE ONTO THE TOP OF IT.

AND WHEN THE CONCRETE HAS SET, THEY'VE COME IN AND THEY'VE REMOVED, DUG OUT ALL OF THAT DIRT.

IT'S ALMOST LIKE A REVERSE JELLY MOLD.

NARRATOR: THESE STRUCTURES ARE AIRCRAFT HANGERS, CUT BACK INTO THE HILLSIDE AND COVERED IN JUNGLE TO BE INVISIBLE TO AMERICAN AERIAL RECONNAISSANCE.

BUILDING THESE AIRFIELDS IS A HUGE UNDERTAKING, AND WITH LITTLE ACCESS TO HEAVY MACHINERY, THE JAPANESE ARMY CONSCRIPT 25,000 LOCAL OKINAWANS.

OVERSEEING OKINAWA'S DEFENSE WITH YAHARA IS HIS IMMEDIATE SUPERIOR, MAJOR GENERAL ISAMU CHO.

BUT THESE TWO MEN COULD NOT BE MORE DIFFERENT.

I'M GOING TO TEACH YOU ARMY TACTICS THAT WILL ASSURE VICTORY!

HOLLAND: CHO IS A TOTALLY DIFFERENT KETTLE OF FISH.

HE'S ULTRA-NATIONALISTIC, HE BUYS INTO ALL THE OLD SAMURAI THINKING.

HE'S VERY, VERY GUNG HO.

WHEN YOU'RE THINKING OF YOUR SWORD-WIELDING JAPANESE COMMANDERS, THAT'S CHO.

NARRATOR: THESE TWO VERY DIFFERENT MEN FREQUENTLY CLASH OVER STRATEGY.

BUT ON ONE THING, THEY'RE IN TOTAL AGREEMENT.

IMPERIAL HEADQUARTERS' INSISTENCE UPON BUILDING THESE AIRFIELDS IS A TOTAL FANTASY.

WE CAN'T RELY ON THE PROMISE OF AIRCRAFT.

I DOUBT WE'LL HAVE THE AIRCRAFT TO EVEN DEFEND THE AIRSTRIPS.

THEY WILL JUST BE TAKEN OVER BY THE AMERICANS.

NARRATOR: AWARE OF JAPAN'S DWINDLING RESOURCES AND AMERICA'S GROWING AIR SUPERIORITY, THEY BELIEVE AIRFIELDS ALONE WON'T BE ENOUGH.

HOLLAND: CHO AND YAHARA REALIZE THAT ACTUALLY VERY SOON, THEY ARE GOING TO BE ON THE FRONT LINE AND OKINAWA NEEDS TO BE MADE SAFE AGAINST THE THREAT OF U.S.

INVASION, AND THAT MEANS BUILDING DEFENSES.

NARRATOR: YAHARA AND CHO BEGIN FORTIFYING THE ISLAND...

STARTING WITH THE COASTLINE.

POLLARD: THE JAPANESE EXPECTED THE AMERICANS TO LAND ON BEACHES IN THE WEST, WHICH IS HERE OR FURTHER TO THE SOUTH.

AND THEY PREPARED THE GROUND BECAUSE THE PLAN WAS TO DESTROY THEM ON THE BEACH.

AND OVER THERE NESTLED UNDER A ROCK OVERHANG IS A CONCRETE PILL BOX.

THE SOLDIERS WOULD HAVE BEEN ENTIRELY UNAWARE OF IT UNTIL IT OPENED UP ON THEM.

NARRATOR: CONSTRUCTION OF A STRING OF DEFENSES BEGINS AROUND THE ISLAND.

THE AIM: TO STOP THE AMERICANS SETTING FOOT ASHORE.

BUT THIS PLAN WILL BE SHORT-LIVED.

YAHARA'S SUPERIORS WILL SOON FORCE HIM TO RETHINK.

IF HE'S TO DEFEAT THE AMERICANS, HE'LL NEED TO WAGE A DIFFERENT KIND OF WARFARE.

AUGUST 1944.

ON THE ISLAND OF OKINAWA, THE BUILDING OF FORTIFICATIONS TO DEFEND AIRFIELDS AND BEACHES IS PROGRESSING.

THE ISLAND CONTINUES TO BE FLOODED WITH REINFORCEMENTS, LIKE 24-YEAR-OLD HAJIME KONDO.

LOOK AT THIS PLACE.

IT'S PARADISE.

NARRATOR: BUT KONDO'S VISION OF PARADISE WILL NOT LAST LONG.

THE WAR IS GOING INCREASINGLY BADLY FOR THE JAPANESE.

THEY'VE ALREADY SUFFERED A CRUSHING DEFEAT IN THE MARIANA ISLANDS AND THE U.S. FLEET DRAWS CLOSER.

OKINAWA WILL SOON BE IN THE FIRING LINE.

AND THEN, IN NOVEMBER 1944, YAHARA RECEIVES ORDERS FROM JAPAN THAT THROW HIS ENTIRE PLAN INTO TURMOIL.

IMPERIAL HEADQUARTERS HAVE ISSUED ORDERS FOR OUR FINEST DIVISION TO BE REDEPLOYED TO THE PHILIPPINES.

THE 9TH DIVISION?

BUT WE ARE RELYING ON THEM TO DEFEND THE BEACHES, ARE WE NOT?

YES.

25,000 MEN AND THE BEST WE HAVE.

HOW EXACTLY DO THEY SUPPOSE WE SHOULD DEFEND THIS ISLAND?

HOLLAND: THE 9TH DIVISION IS THE BEST TRAINED OF ALL THE DIVISIONS IN THE 32ND ARMY.

AND THIS IS A HAMMER BLOW.

NARRATOR: CHO AND YAHARA NOW BELIEVE U.S.

TROOPS WILL FAR OUTNUMBER THEM.

AND WORSE, THERE'S NO SIGN OF THE AIRCRAFT PROMISED TO THE DEFENSE OF THE ISLAND.

YAHARA FACES AN UPHILL STRUGGLE TO WIN THIS BATTLE.

HE NEEDS NEW TACTICS TO ENGULF THE AMERICAN ADVANCE IN A BRUTAL WAR OF ATTRITION.

THIS REALIZATION IS GIVEN CREDENCE BY EVENTS ON THE OTHER SIDE OF THE WORLD.

JAPAN'S GERMAN ALLIES HAD BUILT A MASSIVE DEFENSIVE WALL TO PREVENT AN ALLIED INVASION OF MAINLAND EUROPE.

THIS EXTRAORDINARY LINE OF CONCRETE BUNKERS AND COASTAL GUN BATTERIES STRETCHES OVER 3,000 MILES FROM NORWAY TO THE SPANISH BORDER.

BUT ON D-DAY, THE ALLIES BREACH THE LINE IN A MATTER OF HOURS.

YAHARA WILL TAKE A COMPLETELY DIFFERENT APPROACH.

HIS AUDACIOUS PLAN IS TO ABANDON SOME AIRFIELDS AND MANY OF HIS COASTAL DEFENSES.

HE'LL LET THE AMERICANS LAND UNOPPOSED AND DEFEND IN DEPTH; SETTING A TRAP THAT WILL SLAUGHTER THE ENEMY AS THEY VENTURE INLAND.

HOLLAND: THIS IS ABOUT HOLDING OFF THE AMERICANS FOR AS LONG AS POSSIBLE TO GIVE THE HOME ISLANDS OF JAPAN THE GREATEST POSSIBLE CHANCE THAT THEY CAN.

YOU JUST KEEP THE AMERICANS FIGHTING AND FIGHTING AND FIGHTING AND YOU DON'T GIVE AN INCH.

NARRATOR: BY DECEMBER 1944, JAPANESE FORCES HAVE BEEN UNABLE TO HALT THE AMERICAN ADVANCE THROUGH THE PHILIPPINES.

YAHARA MUST ACT FAST.

HIS PLAN IS TO TAKE HIS ENTIRE ARMY, MORE THAN 100,000 MEN, UNDERGROUND.

POLLARD: THE ROCK ITSELF IS PERFECT FOR THE TASK.

THIS IS A CORAL LIMESTONE AND IT'S VERY STRONG BUT IT'S POROUS.

AND ALL OF THE LITTLE AIR POCKETS IN IT GIVE IT SHOCK-ABSORBING QUALITIES.

SO, AS FAR AS PROTECTION FROM BOMBARDMENT IS CONCERNED, IT'S JUST AS IF NOT BETTER THAN CONCRETE.

NARRATOR: THE BEDROCK PROVIDES YAHARA WITH THE SOLUTION TO A MAJOR PROBLEM.

ATTACKS ON SHIPPING HAVE MEANT CONCRETE AND STEEL ARE SCARCE.

HE MAKES EACH UNIT RESPONSIBLE FOR THEIR OWN SERIES OF TUNNELS.

IT FORCES TROOPS LIKE KONDO TO DIG DEEP.

MAN AS KONDO: THERE WERE SO MANY OF US DETERMINED TO MAKE A STAND, FOR BY DEFENDING OKINAWA, WE WERE DEFENDING JAPAN.

POLLARD: THIS IS ALL HAND-CUT.

INCREDIBLY HARD WORK.

THEY DIDN'T HAVE ANY MACHINES FOR THIS JOB.

AND YOU CAN SEE HERE, THERE'S A LITTLE NICHE.

A LITTLE SHELF HAS BEEN CARVED INTO THE SIDE OF THE PASSAGE, AND THIS WOULD'VE HAD A TALLOW CANDLE IN IT TO PROVIDE LIGHTING.

IT REALLY ISN'T A VERY COMFORTABLE PLACE.

AND KNOWING WHILE ALL THAT WORK'S GOING ON, THE PURPOSE TO WHICH IT'S GOING TO BE PUT.

IT'S NOT HAPPY DAYS AT ALL.

NARRATOR: DESPITE THE HARDSHIPS, THE JAPANESE SUCCEED IN BUILDING HIGHLY COMPLEX FRONTLINE TUNNEL SYSTEMS.

THEY COMMONLY HAVE FIRING POSITIONS TO THE FRONT, SIDE PASSAGES AND EXITS TO THE REAR, AS WELL AS CHAMBERS FOR STORAGE AND ACCOMMODATION.

POLLARD: THIS REALLY OPENS OUT HERE.

OH, LOOK, WHAT'S THIS?

OH, WOW.

OHH.

PUSHED AWAY IN THE CORNER, THESE ARE CARRYING CASES FOR FUSES FOR SHELLS.

LOOKING AT THE SIZE OF THEM, THEY'RE PROBABLY ANTI-TANK ROUNDS.

THE POSITION ITSELF WHERE THIS GUN WAS LOCATED ISN'T IN HERE, BUT THE FUSES MAY HAVE BEEN STORED IN HERE FOR TRANSPORT ELSEWHERE.

BECAUSE THE POINT IS THAT LOOK UP THERE, LOOK, THERE'S ANOTHER PASSAGEWAY.

THIS IS A NETWORK OF TUNNELS.

NARRATOR: YAHARA DESCRIBES HIS SCHEME AS "SLEEPING TACTICS."

THE JAPANESE WILL DIG IN AND WAIT FOR THE AMERICANS TO COME TO THEM.

POLLARD: THIS ISN'T JUST DIGGING A HOLE AND HIDING IN IT, THIS IS BRINGING THE BATTLE UNDERGROUND.

AND IT'S THIS SYSTEM, THIS STRATEGY WHICH IS GOING TO MAKE THE AMERICANS FIGHT FOR EVERY SQUARE INCH OF THIS ISLAND.

NARRATOR: DECEMBER, 1944.

WITH AMERICAN FORCES GETTING CLOSER EVERY DAY, THE CONSTRUCTION OF MILES OF UNDERGROUND FORTIFICATIONS CONTINUES UNDER OKINAWA.

COLONEL YAHARA BELIEVES THE AMERICANS ARE MOST LIKELY TO LAND ON BEACHES TO THE NORTH.

SO, HE SETS OUT HIS DEFENSES IN A SERIES OF LINES SPANNING THE ISLAND.

EACH ONE ABLE TO SUPPORT THE NEXT, AND ENDING WITH THE MAIN SHURI LINE, RUNNING FOR 8 MILES FROM COAST TO COAST.

AND IT'S FROM HERE AT SHURI CASTLE THAT YAHARA AND CHO WILL COMMAND THEIR ARMY.

BENEATH THE 14TH-CENTURY FORTRESS, NOW REBUILT FOLLOWING ITS DESTRUCTION DURING THE WAR, ARE THE REMAINS OF THE ARMY'S MAIN HEADQUARTERS.

POLLARD: THIS TUNNEL SYSTEM HAS BEEN CUT THROUGH THE ROCK BENEATH SHURI CASTLE, BUT IT'S GOT THE ADDED FINESSE OF THESE MASSIVE CONCRETE BULWARKS.

NOW, UNFORTUNATELY, I CAN'T GET IN BECAUSE THEY'RE BLOCKED FOR THE MOST PART, BUT IT WAS FROM HERE THAT THE DEFENSE OF THE ENTIRE SHURI LINE WAS CONTROLLED.

NARRATOR: THE TUNNELS STRETCH FOR AROUND 1,300 FEET, A MAZE OF CODE ROOMS, CONFERENCE ROOMS, AND OFFICER'S QUARTERS.

160 FEET DOWN AT THEIR DEEPEST POINT, THE JAPANESE ANTICIPATE THEY WILL BE TOTALLY BOMBPROOF.

IN THESE COMMAND TUNNELS, THERE ARE A FEW COMFORTS.

FURNITURE AND ELECTRICITY.

BUT WITH OVER 1,000 TROOPS CRAMMED INSIDE, LIFE HERE ISN'T WITHOUT ITS HARDSHIPS.

MAN AS YAHARA: THE ATMOSPHERE IS HOT AND HUMID.

WITH ELECTRIC LIGHTS BURNING DAY AND NIGHT.

IT'S DISORIENTING.

NIGHTLESS.

NARRATOR: BUT COMMANDING THE COMING BATTLE FROM UNDERGROUND WILL CREATE A NEW CHALLENGE.

THE JAPANESE KNOW THAT TO STAND A CHANCE, THEY'LL NEED TO CAREFULLY COORDINATE DISTANT FRONTLINE UNITS WHO ARE ALSO HIDDEN IN MILES OF TUNNELS.

EFFECTIVE COMMUNICATION WILL BE VITAL.

HISTORIAN MARK WAYCASTER IS HEADING TO EXPLORE A JAPANESE COMMAND POST.

THE CRUCIAL LINK BETWEEN THE SHURI HEADQUARTERS AND FRONTLINE TROOPS.

HERE, THE JAPANESE HAVE ADAPTED A NATURAL CAVE SYSTEM.

WAYCASTER: THIS BOXED-IN AREA PROBABLY WAS USED AS A CONFERENCE ROOM.

AND OFF OF THIS WALL WOULD HAVE BEEN WOODEN POSTS AND THEN A CANVAS COVER THAT WOULD'VE BLOCKED ANY KIND OF LIGHT OR SOUND FROM GETTING ANY FURTHER BACK, SO, NO ONE COULD REALLY HEAR WHAT WAS HAPPENING HERE.

NARRATOR: OFFICERS HERE WOULD RECEIVE COMMUNICATIONS FROM ARMY HQ AND THEN DIRECT THEM TO THEIR SPECIFIC UNITS ON THE BATTLEFRONT.

IN THE WARREN OF HAND-CHISELED TUNNELS BEYOND THE NATURAL CAVE IS EVIDENCE OF HOW THEY STAYED CONNECTED.

WAYCASTER: THIS RIGHT HERE WAS ACTUALLY A SPOT FOR A RADIO FOR THIS PIECE OF TUNNEL.

THEY WOULD'VE PLACED A RADIO SET BACK IN HERE.

THAT RADIO SET WOULD BE SET IN HERE, BRACED ON EITHER SIDE BY TIMBER SUPPORTS, AND THEN THE ACTUAL ANTENNAE WOULD BE RAN OUTSIDE OF THE CAVE AND THE UP ON THE HILL UP ABOVE US.

NARRATOR: THESE RADIOS WOULD ALLOW ORDERS FROM THE MAIN SHURI HEADQUARTERS TO REACH THESE FORWARD COMMAND POSTS FAST.

BUT THE JAPANESE ONLY HAVE RADIOS CONNECTING THESE TOP-LEVEL COMMANDERS.

TO GET MESSAGES TO AND FROM FRONTLINE UNITS FROM HERE, THEY'LL RELY ON MORE PRIMITIVE FIELD TELEPHONES.

IT WILL BE CRUCIAL THAT THESE LINES ARE KEPT OPEN DURING THE BATTLE.

TONY POLLARD HAS DISCOVERED MORE CAVES, WELL BEHIND THE FRONT LINES, THAT WOULD RELY TOTALLY ON STAYING CONNECTED.

POLLARD: I MEAN, IT LOOKS VERY ROUGH AND READY, BUT IT'S QUITE A FEAT OF ENGINEERING.

THERE'S A LOT OF WORK GONE ON IN HERE.

OH.

THERE'S AN OPENING HERE INTO A SIDE CHAMBER.

AND A RAMP RUNNING UP TO DAYLIGHT UP THERE.

DOWN HERE IN THIS OPEN AREA THERE WOULD HAVE BEEN A GUN, AND THE GUN IS PROBABLY POINTING INTO THE CAVE.

IT'S NOT POINTING OUTSIDE.

THEY WOULD WHEEL IT OUT INTO THE COURTYARD, CRANK IT UP, AND FIRE IT OVER THE TOP OF THE RIDGE.

SO, THIS IS INDIRECT FIRE FROM A REVERSE SLOPE POSITION.

NARRATOR: THESE ARE ARTILLERY CAVES.

BY PREDICTING WHICH WAY THE ENEMY IS LIKELY TO ADVANCE, THEN POSITIONING GUNS ON THE REVERSE SLOPES, THEY ARE KEPT OUT OF VIEW FROM THE ENEMY AND PROTECTED BY THE RIDGE.

ON RECEIVING COORDINATES BY COMMUNICATIONS OR FROM SPOTTERS IN A CAVE ON THE FORWARD SLOPE...

THE ARTILLERY WOULD FIRE A SMALL NUMBER OF ROUNDS BEFORE BEING WHEELED BACK INTO THE CAVE FOR PROTECTION.

THIS SO-CALLED "SNIPING" TECHNIQUE PROVES EFFECTIVE IN KEEPING THE JAPANESE ARMY'S BIG GUNS HIDDEN AND PROTECTED...

WHILE IN ANOTHER PART OF THE TUNNEL SYSTEM, OTHER SMALLER ARTILLERY PIECES WOULD BE TRAINED DIRECTLY ON THE U.S.

FORCES.

POLLARD: IT WILL BE INTERESTING TO SEE WHAT THE VIEW TELLS US ABOUT THE FUNCTION OF THIS PLACE.

UHH.

THIS OPENING GIVES AN INCREDIBLY GOOD VIEW OVER THE FLAT GROUND BELOW.

THERE'S A RIVER CROSSING WHICH I CAN SEE CLEARLY FROM HERE.

THIS OPENING HAS BEEN CARVED DELIBERATELY TO GIVE A VIEW DOWN ONTO THAT ROAD AND THAT CROSSING.

AND IT'S LIKELY GIVEN THE SMALL SIZE OF THIS OPENING, WE'RE LOOKING AT AN ANTI-TANK GUN THAT WOULD BE DESIGNED TO HIT MOBILE ARMOR AND KNOCK IT OUT.

AND YOU CAN SEE THE TROUBLE THEY'VE GONE TO.

THIS ISN'T NATURAL ROCK HERE.

THEY'VE SMEARED CONCRETE OVER THE OPENING OF THE CAVE TO GIVE IT EXTRA STRENGTH BECAUSE IT'S GOING TO BE CREATING SHOCK.

SO, THEY NEED TO MAKE SURE THEY DON'T GET ROCK FALLS, AND THERE ARE IMPRESSIONS IN THE CONCRETE IN THE SIDE, SO, THEY'VE ALSO BEEN ADDING EXTRA PROTECTION WITH TIMBER SET INTO THIS CONCRETE.

AND OVER THAT DISTANCE, ANYTHING DOWN ON THAT ROAD, REALLY, IS A SITTING DUCK AS FAR AS THIS POSITION IS CONCERNED.

NARRATOR: THE CAREFUL PLACACACT OF ARTILLERY CAVES IS A TOP PRIORITY FOR YAHARA.

HE INTENDS TO GROUP MOST OF HIS FIREPOWER RIGHT BEHIND THE CENTER OF HIS DEFENSIVE POSITIONS.

IF WE BREAK UP THE ARTILLERY INTO DIFFERENT LOCATIONS, WE WILL LOSE ITS EFFECTIVENESS.

SO, PLACED HERE, IT GIVES US THE MOST OPTIONS.

WE'LL BE ABLE TO BRING ALL OF OUR FIREPOWER TO BEAR ANYWHERE ALONG THE BATTLEFRONT.

POLLARD: I THINK WHEN YOU'RE TALKING ABOUT SOLDIERS HIDING IN CAVES, IT GIVES TOTALLY THE WRONG IMPRESSION.

THAT'S NOT WHAT THE JAPANESE ARE DOING ON OKINAWA.

THESE CAVES ARE IN VERY STRATEGIC POSITIONS.

THEY ALLOW THE JAPANESE TO HAVE EXCELLENT HIDING PLACES THAT ALSO GIVE THEM SUPERB OUTLOOK ONTO THE ENEMY.

THIS IS ABSOLUTELY PERFECTLY SITED.

GENIUS, REALLY.

NARRATOR: BY THE END OF MARCH 1945, YAHARA'S TRAP IS SET.

THE ISLAND'S LABYRINTH OF 60 MILES OF TUNNELS, BUNKERS, AND KILLER FORTIFICATIONS IS READY JUST IN TIME.

OFF THE COAST, ALMOST 1,500 ALLIED SHIPS ARE BEARING DOWN ON OKINAWA.

THEY HAVE NO IDEA WHAT LIES IN WAIT.

APRIL 1, 1945.

05:30 HOURS.

HAJIME KONDO AND 100,000 OTHER JAPANESE SOLDIERS TAKE COVER BENEATH THE BEDROCK AS THE FIRST SALVOS OF A MASSIVE ONSLAUGHT RAIN IN ON OKINAWA.

[EXPLOSIONONONONON] JUST OFF THE COAST, THE ALLIED FLEET, THE BIGGEST EVER ASSEMBLED IN NAVAL HISTORY, HAS LAUNCHED "OPERATION ICEBERG."

A RELENTLESS PRE-LANDING BOMBARDMENT THROWS MORE THAN 100,000 SHELLS AND ROCKETS AT OKINAWA OVER A 3-HOUR PERIOD.

WAYCASTER: THEY DROP OVER 4,500 TONS OF ORDNANCE ON THAT BEACH.

IT'S THE HEAVIEST PREPARATORY BOMBARDMENT FOR AN AMPHIBIOUS INVASION IN WORLD HISTORY.

[WHISPERING] The tunnel is holding.

THEY CAN'T GET TO US DOWN HERE.

HOLLAND: IN THE INITIAL BOMBARDMENT, THEY'RE JUST HURTLING OVER VAST NUMBERS OF SHELLS.

BUT THE JAPANESE ARE IN THEIR TUNNELS.

IT'S UNPLEASANT, THE GROUND IS SHAKING, THERE'S LOTS OF DAMAGE ON THE SURFACE, BUT IN ACTUAL FACT IN TERMS OF HOW IT AFFECTS THEM AS A FIGHTING FORCE, IT HAS VERY LITTLE IMPACT AT ALL.

NARRATOR: DEEP BEHIND THEIR HEAVILY DEFENDED RIDGES AT THE MAIN SHURI LINE, JAPANESE COMMANDER, RECENTLY PROMOTED, LIEUTENANT GENERAL ISAMU CHO AND HIS SUPERIOR WATCH THE FIRST WAVE OF AMERICAN TROOPS COME ASHORE.

IT IS DIFFICULT TO WATCH THEM LAND UNOPPOSED BUT THEY WILL SOON KNOW WE ARE HERE.

HOLLAND: THIS IS ONE OF THE BIGGEST AMPHIBIOUS OPERATIONS OF THE ENTIRE WAR.

I MEAN, ON D-DAY IN NORMANDY, THE ALLIES LAND 6 DIVISIONS.

ON OKINAWA, THEY LAND 7.

SO, THERE'S ACTUALLY A DIVISION MORE THAN IN NORMANDY.

ALL THE TROOPS HAVE BEEN WARNED TO EXPECT FIERCE, FIERCE OPPOSITION.

AND THEY GO ONTO THE BEACHES AND NOTHING HAPPENS.

YOU CAN JUST IMAGINE HOW TENSE YOU'D BE FEELING.

SUDDENLY, THEY START TO GET THEIR CONFIDENCE.

THEY REALIZE THAT THEY'RE UNOPPOSED.

AND THEY START MOVING INLAND.

AND BEFORE THE END OF THE DAY, THEY'VE GOT A BRIDGEHEAD OF SOME 3 MILES.

AND THEN THEY MOVE ON AND TAKE THE AIRFIELDS.

AND THE AIRFIELDS ARE KIND OF LARGELY UNDEFENDED AND EVERYONE'S THINKING, GOD, THIS IS GONNA BE A CAKEWALK AFTER ALL.

NARRATOR: OVER THE NEXT FEW DAYS, THE JAPANESE ALLOW U.S. MARINES TO STRIKE NORTH, WHERE THEY ENCOUNTER ONLY SPORADIC RESISTANCE.

BUT AS THE INVASION FORCE HEADS SOUTH TOWARDS THE SHURI LINE, EVERYTHING IS ABOUT TO CHANGE.

APRIL 8, A WEEK AFTER THE LANDINGS.

THE JAPANESE SEE AMERICANS APPROACHING YAHARA'S FIRST MAJOR DEFENSIVE LINE AT KAKAZU RIDGE.

EXPLORING IT IS HISTORIAN MARK WAYCASTER.

WAYCASTER: THIS RIGHT HERE IS ONE OF A SERIES OF PILL BOXES THAT WOULD HAVE SAT HERE ON KAKAZU RIDGE.

THIS WOULD BE A FINISHED-OUT WALL COVERED IN DIRT, CAMOUFLAGED IN.

THEY WOULD HAVE NEVER KNOWN IT WAS HERE.

YOU CAN SEE THESE FIRING SLITS.

YOU HAVE ONE HERE AND THEN A SECOND ONE HERE.

THIS GAVE THE JAPANESE A WIDE ARC OF FIRE TO COVER THE VALLEY FLOOR IN FRONT OF THEM.

NARRATOR: AND THIS IS JUST ONE OF A STRING OF PILL BOXES AND HIDDEN FIRING PORTS STRETCHING RIGHT ALONG KAKAZU RIDGE.

BEHIND THEM, A NETWORK OF TUNNELS.

THEIR ELEVATION AT THE TOP OF THE SLOPE GIVES THE JAPANESE A HUGE ADVANTAGE OVER APPROACHING AMERICANS, AND THEY'RE LAID OUT TO FORM A GRIDWORK OF INTERLOCKING FIRE THAT CREATES DEVASTATING KILL ZONES.

WAYCASTER: IT NARROWED THE APPROACHES FOR THE AMERICANS INTO CERTAIN PATHS.

HERE AT OKINAWA, IT TURNS THIS RIDGELINE INTO A BLOODY MESS.

[WHISPERING] Hey, look, they're here.

NARRATOR: IN HIS BUNKER, KONDO SPOTS THE AMERICANS.

MAN AS KONDO: THEIR TANKS CAME FIRST AND THEN THE INFANTRY COMPANIES FOLLOWED.

THE SOLDIERS LOOKED AS THOUGH THEY CAME FOR A PICNIC.

HOLLAND: AS THE AMERICANS ARE APPROACHING, THE JAPANESE ARE BEING ORDERED TO JUST HOLD THEIR FIRE TO THE LAST MINUTE.

THEY'VE LITERALLY GOT TO SEE THE WHITES OF THEIR ENEMY'S EYES BEFORE THEY OPEN FIRE.

WAYCASTER: THIS HAS TO BE NERVE-WRACKING FOR THEM.

THEY SEE THEIR ENEMY ADVANCING, HE'S WELL WITHIN RIFLE SHOT, BUT THEY HAVE TO HOLD.

THEY HAVE TO HOLD.

NARRATOR: THE FIRST LINE OF DEFENSE WORKS WELL FOR THE JAPANESE, STOPPING THOUSANDS OF U.S.

TROOPS IN THEIR TRACKS AND INFLICTING HEAVY CASUALTIES.

BUT FOR THOSE LIKE KONDO, FIGHTING FROM THEIR CONFINED POSITIONS IS A TRULY TERRIFYING EXPERIENCE.

WAYCASTER: LIFE FOR THE JAPANESE IN THIS BUNKER AS THE AMERICANS ADVANCE WOULD HAVE BEEN NERVE-WRACKING.

YOU CAN SEE THE POUNDING ON THE INSIDE THAT THIS BUNKER'S TAKEN.

YOU'VE GOT PIECES OF REBAR THAT ARE JUTTING OUT HERE AND THE ORIGINAL APERTURE WOULD HAVE SAT HERE.

ROUNDS WOULD HAVE BEEN FALLING ALONG THIS ENTIRE RIDGELINE TO SCREEN THE ADVANCE OF THE AMERICANS.

AND THEN ONCE THE ROUNDS THEMSELVES START LANDING HERE, IT MUST HAVE BEEN HORRIFIC FOR THESE MEN.

[JAPANESE SOLDIER SCREAMS] NARRATOR: DURING THE FIGHT, KONDO IS HIT IN THE SHOULDER.

BUT THE TUNNELS ALLOW HIM TO ESCAPE TO AN UNDERGROUND FIELD HOSPITAL... [MAN SHOUTING IN JAPANESE] NARRATOR: DEEP BEHIND THE LINES.

[GROANS] NARRATOR: APRIL 24, BACK AT KAKAZU RIDGE.

AFTER NEARLY 3 WEEKS OF VICIOUS FIGHTING, THE AMERICANS FINALLY TAKE THE HILL.

BUT THEY FIND THE TUNNELS HAVE GIVEN THE ENEMY AN ESCAPE ROUTE.

THE JAPANESE SOLDIERS HAVE SLIPPED AWAY.

BUT ONLY AS FAR AS THE NEXT LINE OF KILLER FORTIFICATIONS.

KAKAZU RIDGE IS JUST ONE OF SEVERAL THAT THEY MUST TAKE BEFORE EVEN REACHING THE INNER SHURI LINE.

THE NEXT IS WHAT THE AMERICANS DUB "HACKSAW RIDGE."

FROM UP ON HACKSAW RIDGE, YOU CAN SEE HOW STRONG THE JAPANESE POSITIONS ARE.

IT LOOKS BACK TO THE NORTH TO THE FIRST LINE OF DEFENSE, COMING AROUND TO KAKAZU THERE.

FROM UP HERE, ONCE THEY FALL BACK, THEY CAN ACTUALLY SHOOT DOWN ONTO THAT FIRST LINE AS THE AMERICANS START TO TAKE IT, AND I WOULD NOT LIKE TO BE AN AMERICAN SOLDIER CRESTING KAKAZU RIDGE WITH GUNS FIRING FROM HERE.

OVER IN THE BACK, THOUGH, YOU GET THIS STUNNING PERSPECTIVE, BECAUSE YOU CAN SEE JUST HOW EVERY PIECE OF HIGH GROUND IS PEPPERED WITH THESE CAVES AND TUNNELS, AND INDEED OVER THERE, THEY'RE DOING CONSTRUCTION WORK, AND THEY'VE CUT A SLICE THROUGH THE HILL, AND I CAN SEE LOADS OF ENTRANCES AND EVEN TUNNELS BEHIND THEM.

IT'S AN ABSOLUTELY ASTOUNDING BATTLESCAPE.

HOLLAND: ULTIMATELY, WHEN YOU'RE UP AGAINST THAT KIND OF ENEMY WHICH IS DUG INTO THE HILLSIDE, WHICH HAS GOT 60 MILES OF TUNNELS TO PLAY WITH, THERE'S ONLY ONE WAY TO DO THIS.

AND THIS IS BY CAPTURING EVERY FOOT, EVERY YARD, KILLING EVERY JAPANESE SOLIDER YOU COME UP AGAINST.

AND THAT'S AN INCREDIBLY TRAUMATIC, BRUTAL, AND VICIOUS WAY OF FIGHTING A WAR.

NARRATOR: THE JAPANESE ARE DETERMINED TO DEFEND OKINAWA... ONE TUNNEL AT A TIME.

APRIL 26, 1945, 4 WEEKS AFTER THE U.S. LANDINGS ON OKINAWA.

JAPANESE TROOPS FIGHTING FROM THEIR TUNNELS ON HACKSAW RIDGE HALT THE AMERICAN ADVANCE AGAIN.

TONY POLLARD IS EXPLORING THE LABYRINTH OF TUNNELS BENEATH THE RIDGE.

POLLARD: OH, LOOK AT THIS.

LOOK.

THAT IS ALL THAT'S LEFT OF A JAPANESE SOLDIER'S WEAPON.

THAT'S THE MUZZLE END OF A RIFLE.

NARRATOR: THE JAPANESE TROOPS HERE AT HACKSAW RIDGE WOULD USE THEIR TUNNELS TO DEVASTATING EFFECT.

FOR THEM, MOBILITY AND SURPRISE WOULD BE THEIR SECRET WEAPON.

POLLARD: WOW.

NARRATOR: THE REVERSE SLOPE IS RIDDLED WITH TUNNEL EXITS, ALL PART OF YAHARA'S PLAN TO TURN DEFENSE INTO ATTACK.

POLLARD: HERE YOU COULD DO ANYTHING.

YOU'RE OUT OF SIGHT OF THE ENEMY AND THEIR GUNFIRE.

YOU CAN MOVE AROUND FREELY FROM ONE TUNNEL EXIT TO ANOTHER RESUPPLYING AREAS, MOVING TROOPS AROUND, AND THAT'S THE POINT OF THESE SYSTEMS.

IT ALLOWS FLUIDITY OF MOVEMENT UNDERCOVER AND AT A MOMENT'S NOTICE, ANYWHERE ALONG THIS RIDGELINE, TROOPS CAN POP OUT TO TAKE ON THE AMERICANS.

NARRATOR: TIME AND TIME AGAIN, THE JAPANESE LAUNCH SURPRISE ATTACKS THAT REPEL EVERY AMERICAN ATTEMPT TO TAKE THE RIDGE.

BUT THEY SOON COME UP AGAINST A BRUTAL WEAPON THAT WILL COME TO DOMINATE THE BATTLEFIELD.

POLLARD: HERE IN THE MOUTH OF ONE OF THESE TUNNELS CAN ALREADY SEE EVIDENCE OF COMBAT.

THE ROCK HAS BEEN BLACKENED AND THIS IS BECAUSE IT'S BEEN LICKED WITH LIQUID FIRE.

THIS IS THE RESULT OF A FLAME THROWER ATTACK.

NARRATOR: THE AMERICANS HAVE TWO KINDS OF FLAME THROWER.

SMALL HANDHELD UNITS AND FLAME TANKS, CAPABLE OF SHOOTING DEADLY NAPALM UP TO 300 FEET.

POLLARD: THIS WAS A WEAPON THAT WAS INCREDIBLY EFFECTIVE AGAINST TUNNELS AND CAVES AND THE JAPANESE WERE TERRIFIED OF IT.

THE FRONT PART OF THIS ENTRANCE PASSAGE HAS JUST BEEN SHEETED WITH THIS FIRE, AND I CAN SEE IT GOES IN FOR SOME DISTANCE.

A TRULY AWFUL DEVICE.

NARRATOR: BUT THE JAPANESE KNEW THEY'D FACE THIS THREAT AND HAD BUILT A DEFENSE INTO THE STRUCTURE OF THE TUNNELS.

POLLARD: ONE OF THE FEW DEFENSES THAT THE JAPANESE COULD COME UP WITH WERE RIGHT ANGLES, BECAUSE THOSE FLAMES MIGHT BE ABLE TO SHOOT DOWN A PASSAGE, BUT THEY CAN'T SHOOT AROUND CORNERS.

SO, HERE WE HAVE A VERY GOOD EXAMPLE OF THAT.

A QUITE ACUTE RIGHT ANGLE DESPITE THE JAGGED NATURE OF THE ROCKS.

SO, IF AN AMERICAN SOLDIER WITH A FLAME THROWER IS HERE, ALL I HAVE TO DO IS DODGE AROUND HERE, GIVE MYSELF A LITTLE BIT OF DISTANCE, AND HOPEFULLY I'LL SURVIVE THAT BLAST OF LIQUID FIRE.

NARRATOR: IT MAY NOT ALWAYS WORK AGAINST THE MORE POWERFUL FLAME TANKS...

BUT IT GIVES THEM A FIGHTING CHANCE.

THE COMPLEX TUNNEL NETWORKS ALLOW THE JAPANESE ON HACKSAW RIDGE TO HOLD OUT AGAINST OVERWHELMING AMERICAN FORCE FOR 10 DAYS.

BUT IT'S ALSO DOWN TO ANOTHER JAPANESE TACTIC.

THEY'VE HARNESSED TRADITIONAL SAMURAI CODES OF HONOR TO INSTILL A WILLINGNESS TO FIGHT TO THE DEATH.

HOLLAND: IT BECOMES ABSOLUTELY THE CENTRAL FOCUS OF MILITARY DISCIPLINE WITHIN THE JAPANESE ARMY, AND IT'S INCREDIBLY EFFECTIVE BECAUSE PEOPLE ACCEPT THAT IT IS AN HONOR TO DIE FOR THEIR EMPEROR.

DETERMINED, DISCIPLINED FIGHTERS WHO SIMPLY DON'T WANT TO SURRENDER.

THAT MAKES THEM VERY, VERY TOUGH, EVEN WHEN THEIR WEAPONS ARE INFERIOR, THEIR NUMBERS INFERIOR, AND THEIR WAR MATERIAL IS INFERIOR.

NARRATOR: JAPANESE TROOPS ARE ALSO TOLD THE AMERICANS ARE MONSTERS WHO'LL TORTURE AND KILL THEM IF THEY'RE TAKEN ALIVE.

BUT HAJIME KONDO, RECOVERED FROM HIS INJURIES AND NOW FIGHTING TO HOLD THE MAIN SHURI LINE, REALIZES THE AMERICANS ARE NOT SO DIFFERENT.

MAN AS KONDO: I SAW SEVERAL PEOPLE DIE IN THE WAR.

THE JAPANESE SOLDIER'S LAST WORD WAS USUALLY "MOTHER."

WHEN WE SHOT AMERICANS, WE ALSO HEARD THEM CALLING FOR THEIR MOTHERS.

WE TALKED ABOUT IT, HOW WHEN THEY WERE DYING THEY SAID THE SAME THING AS US.

NARRATOR: BY THE END OF APRIL, 1945, ALL IS GOING TO PLAN FOR COLONEL HIROMICHI YAHARA.

HIS DEFENSIVE STRATEGY IS RESTRICTING THE AMERICANS' ADVANCE TO JUST 100 YARDS A DAY.

BUT SOMETHING'S ABOUT TO HAPPEN THAT WILL PUT HIS ENTIRE PLAN IN JEOPARDY.

HIS SUPERIOR, LIEUTENANT GENERAL CHO, IS TIRED OF SOAKING UP THE PUNISHMENT.

HE WANTS TO TAKE THE BATTLE TO THE AMERICANS.

WE MUST LAUNCH A COUNTEROFFENSIVE WHILE WE STILL CAN.

RATHER THAN HIDE IN CAVES AND WAIT TO DIE, WE MUST FIGHT!

TO TAKE THE OFFENSIVE NOW, WITH INFERIOR FORCES, IS RECKLESS AND WOULD LEAD TO CERTAIN FAILURE.

A NEEDLESS WASTE OF OUR TROOPS.

I BELIEVE WE CAN SNATCH LIFE FROM THE MIDST OF DEATH.

WE MUST LAUNCH AN OFFENSIVE.

NARRATOR: MAY 4, 04:50 HOURS.

JAPANESE ARTILLERY OPENS UP, FIRING 13,000 ROUNDS IN SUPPORT OF THE OFFENSIVE.

BUT AGAINST OVERWHELMING U.S.

FIREPOWER, IT QUICKLY PROVES FUTILE.

HOLLAND: GOING OUT ACROSS NO MAN'S LAND, CHARGING AND WIELDING SWORDS AND FIRING FROM THE HIP, AGAINST THE AMERICANS, THAT'S JUST NOT GOING TO WORK, AND, OF COURSE, THEY ALL GET COMPLETELY MOWED DOWN.

NARRATOR: IN TWO DAYS, THE JAPANESE LOSE 7,000 MEN AND DOZENS OF ARTILLERY PIECES THAT HAD BEEN MOVED INTO ATTACK POSITIONS TO SUPPORT THE OFFENSIVE.

IT'S A DISASTER.

THE JAPANESE REVERT BACK TO YAHARA'S DEFENSIVE STRATEGY, BUT HE KNOWS THE LOSSES WILL HAVE BADLY DAMAGED THEIR ABILITY TO PROLONG THE FIGHT.

AND IN THE TUNNELS OF A COMMAND POST, MARK WAYCASTER FINDS EVIDENCE OF HOW OTHER AREAS OF YAHARA'S WAR MACHINE ARE BEGINNING TO STRUGGLE.

WAYCASTER: IF YOU LOOK DOWN HERE, YOU'VE GOT THIS TUNNEL THAT IS CUT THROUGH HERE.

IT'S EXTREMELY NARROW, IT'S SHORT.

THIS RIGHT HERE WOULD HAVE BEEN THE PERFECT SIZE FOR MESSENGERS.

MESSENGERS TENDED TO BE SMALLER.

I MEAN, HERE ON OKINAWA, THEY USE OKINAWAN CHILDREN.

NARRATOR: WITH MANY FIELD TELEPHONE LINES CUT BY ENEMY SHELLS, THE JAPANESE RELY ON CHILDREN TO CARRY MESSAGES FROM ONE TUNNEL SYSTEM TO ANOTHER.

WAYCASTER: THEY COULD OFFICIALLY RANGE IN AGE FROM 15 TO 17.

REALISTICALLY, THERE ARE ACCOUNTS OF AS YOUNG AS 12 YEARS OLD.

SPACE LIKE THIS IS PERFECT FOR SOMEONE THAT SIZE.

NARRATOR: THEIR RELIANCE ON YOUNG RUNNERS TO RELAY ORDERS IS A MAJOR WEAKNESS.

[SHOUTS INDISTINCTLY] TAKE THIS MESSAGE TO THE GENERAL.

HURRY.

NARRATOR: INSIDE THE TUNNELS, THEY CAN MOVE AROUND SAFE AND UNSEEN, BUT TO GET BETWEEN TUNNEL SYSTEMS, THEY MUST WAIT UNTIL NIGHTFALL.

[EXPLOSION] IT'S DANGEROUS AND VERY SLOW.

AND THESE DELAYS HAVE SERIOUS CONSEQUENCES, ESPECIALLY FOR FRONTLINE TROOPS IN NEED OF ARTILLERY SUPPORT.

IT COULD TAKE 6 HOURS FOR A MESSENGER TO GET BACK BEHIND THE LINES TO THE BIG GUNS.

FAR TOO LONG, ESPECIALLY WHEN UP AGAINST MOVING TARGETS, LIKE TANKS.

BY THE TIME THEY GET READY TO FIRE THAT FIRE MISSION, THE AMERICANS ARE ALREADY LONG GONE AND IN A COMPLETELY DIFFERENT POSITION.

IT REALLY MAKES THE ARTILLERY GROUP HERE COMPLETELY USELESS.

NARRATOR: BY MID-MAY, 1945, AFTER 7 WEEKS OF VICIOUS FIGHTING, THE EDGES OF YAHARA'S MAIN SHURI LINE FINALLY BEGIN TO CRUMBLE.

HIDDEN IN THEIR UNDERGROUND HEADQUARTERS, YAHARA AND CHO KNOW THEY CAN'T HOLD OUT MUCH LONGER.

THE JAPANESE ARE ABOUT TO MAKE THEIR LAST THROW OF THE DICE.

MAY 27, 1945.

YAHARA REALIZES THE AMERICANS ARE CLOSE TO BREAKING THROUGH HIS MAIN SHURI LINE.

HE ORDERS THE ARMY TO ABANDON ITS SHURI HEADQUARTERS AND RETREAT TO THE FAR SOUTH OF THE ISLAND IN AN ATTEMPT TO DRAW OUT THE BATTLE YET FURTHER.

BUT BY THE NIGHT OF JUNE 21, 1945, THE JAPANESE ARMY COMMANDERS ARE CORNERED IN A CAVE WITH THE AMERICANS JUST 400 YARDS AWAY.

WITH THE REALIZATION THAT THE BATTLE IS LOST, CHO ORDERS YAHARA TO TRY TO ESCAPE.

CHO WILL REMAIN ON THE ISLAND.

FOR FUTURE GENERATIONS, YOU WILL BEAR WITNESS TO HOW I DIED.

NARRATOR: BEFORE THE FOLLOWING DAWN, CHO AND HIS COMMANDING OFFICER COMMIT SEPPUKU, RITUAL SUICIDE.

SELF-DISEMBOWELMENT FOLLOWED BY SWIFT DECAPITATION.

WITH ORGANIZED JAPANESE RESISTANCE DISINTEGRATING, U.S.

TROOPS TRY TO COAX PETRIFIED CIVILIANS AND SOLDIERS FROM THEIR CAVES.

THEY DON'T ALWAYS SUCCEED.

MANY CHOOSE TO COMMIT SUICIDE...

WHILE OTHERS, LIKE KONDO AND WHAT REMAINS OF HIS BATTALION, DECIDE THEY'LL GO DOWN IN A FINAL BANZAI ATTACK.

MAN AS KONDO: IT WAS SUICIDAL BEHAVIOR, BUT I BELIEVED THAT DEATH WOULD BE A KIND OF RELIEF FOR US.

NARRATOR: BUT KONDO IS CAPTURED.

EASY, PAL.

HUH?

NARRATOR: HE EXPECTS TO BE SHOT.

BUT INSTEAD HE'S HELPED TO RECOVER.

HE'S ONE OF A LUCKY FEW TO SURVIVE.

HOLLAND: THE HARSH REALITY IS THAT ALMOST ALL OF THOSE JAPANESE THAT HAVE FOUGHT ON OKINAWA, AT THE END OF IT, NEARLY ALL OF THEM ARE DEAD.

NARRATOR: MORE THAN 12,000 AMERICANS ARE KILLED DURING THE BATTLE AND OVER 77,000 JAPANESE SOLDIERS.

AROUND 150,000 OKINAWAN CIVILIANS ALSO PERISH; SOME CONSCRIPTED BUT MOST JUST CAUGHT UP IN THE FIGHTING.

I'VE SEEN A LOT OF WAR MEMORIALS IN MY TIME BUT NOTHING LIKE THIS.

LOOKING AT THESE CHARACTERS ON THIS MARBLE REALLY DRIVES HOME JUST HOW SHOCKING THIS BATTLE WAS.

THERE WERE NO RULES OF WAR HERE.

THIS REALLY WAS A BATTLE OF ANNIHILATION.

AND TO BE QUITE FRANK, WORDS DON'T REALLY DO IT JUSTICE.

NARRATOR: OKINAWA'S VAST NETWORK OF UNDERGROUND FORTIFICATIONS AND THE JAPANESE DETERMINATION TO FIGHT TO THE DEATH PROVOKES THE AMERICANS INTO THEIR NEXT MOVE, TO USE A MEGA-WEAPON OF THEIR OWN MAKING.

HOLLAND: WHAT THE AMERICANS REALIZE IS THAT THE CLOSER THEY'VE BEEN GETTING TO THE JAPANESE HOME ISLANDS, THE BLOODIER THE BATTLE HAS BEEN.

THE HARDER THE JAPANESE HAVE BEEN DEFENDING.

NEXT ON THE LIST IS THOSE HOME ISLANDS OF JAPAN, AND NO ONE'S GOT THE STOMACH FOR IT.

AND SUDDENLY EMERGING IN THOSE DESERTS OF NEW MEXICO IS AN ALTERNATIVE MEANS OF GETTING THE JAPANESE OUT OF THE SECOND WORLD WAR, AND THAT, OF COURSE, IS THE ATOMIC BOMB.

NARRATOR: THE TERRIBLE DESTRUCTION OF TWO ATOMIC BOMBS PERSUADES JAPAN TO SURRENDER ON AUGUST 15, 1945.

THE WAR IS OVER.

COLONEL YAHARA IS CAPTURED HIDING AMONG OKINAWAN CIVILIANS.

HE'S LATER RELEASED BUT AS THE ONLY SENIOR COMMANDER TO BE TAKEN ALIVE, HE'S CONSIDERED BY MANY IN JAPAN TO BE A DISGRACE TO HIS COUNTRY.

HAJIME KONDO SURVIVES AND RETURNS TO HIS HOME IN JAPAN.

HE WILL DEDICATE MUCH OF HIS LIFE TO TELLING OTHERS OF HIS EXPERIENCE AND THE HORRORS OF WAR.

YAHARA'S TUNNELS WERE AN EXTRAORDINARY TACTICAL SUCCESS, ALLOWING HIS TROOPS TO HOLD OUT FOR 10 WEEKS AGAINST OVERWHELMING FORCES.

BUT IN THE END, THEY WERE NO MATCH FOR THE MIGHTY AMERICAN WAR MACHINE.

THE TUNNELS' GRIM LEGACY: THAT THEY FORCED A BATTLE OF UNRIVALED BRUTALITY THAT KILLED MORE PEOPLE THAN BOTH ATOMIC BOMBS COMBINED.