Original subtitles

[narrator] It is the epicenter of America's military operations.

A five-sided fortress with a single purpose:

to defend the United States and its citizens.

But behind the concrete walls and reinforced windows

of the Pentagon are secrets.

Secrets so guarded...

[Ray Dubois] The country's most sensitive secrets

are held within this building and within certain minds.

[narrator] ...so incredible...

She crawled out with people hanging onto her legs to get out.

[narrator] ...so alarming...

We are already experiencing our 9/11 in cyberspace.

[narrator] ...that they must be kept hidden from the public

until now.

There are those who believe in the existence of a book.

A book that contains the most highly guarded secrets

of the United States of America.

A book whose very existence

is known to only a select few.

But if such a book exists,

what would it contain?

Secret histories?

Secret plans?

Secret lies?

Does there really exist

America's Book of Secrets?

[narrator] It proudly stands on the west bank of the Potomac River

on the edge of Washington, DC.

A building, an institution,

a symbol of America's military might.

The Pentagon.

Here, headquartered under one roof, is the Department of Defense,

the Joint Chiefs of Staff

and the five branches of the U.S. military.

Commands issued from behind these walls

direct the actions of U.S. forces around the world.

The Pentagon is the heart, the soul, the brain

of our national military community.

[Oliver North] It does house the entire top

of the defense establishment of the United States.

It is regarded as an icon, if you will, for enemies and allies.

[Wesley Clark] I was always excited in the Pentagon.

It was always a place where things could happen or be made to happen,

or they happened to you.

But it was never dull. There was always adventure.

[narrator] Perhaps most famous for its unique design,

the Pentagon is the largest low-rise office building in the world.

It occupies more than six million square feet of floor space

and spans an area equal to five city blocks.

Called The Puzzle Palace by insiders,

the labyrinth of hallways and corridors that run through the building

measure 17-and-a-half miles in length.

Yet despite its vast size, the Pentagon's unusual design

allows for quick access to any of its five equal sides.

This design allows someone to get from any point in the building,

the furthest spot you might imagine, from corridor ten

all the way around to corridor two, three or five in seven minutes or less.

[narrator] But for many, the Pentagon

is much more than a monumental building,

it is a living entity.

It's one of the few buildings that you could say that speaks.

You see it in the newspaper quite often, "The Pentagon said..."

If there were an American Book of Secrets, I think what it would say

about the Pentagon is this really is

where the nation's defenses really begin.

[narrator] Approximately 23,000 people,

both military and civilian,

work at the Pentagon every day.

The building is fully operational around the clock,

and includes an infrastructure of transportation,

food services and retail shops enlisted to support the enormous staff.

But what is the secret to keeping the Pentagon operational 24/7?

[Erin Mahan] I think what would surprise most people, and it certainly did me

when I came to work at the Pentagon, is that it's not just an office building.

It's really a city unto itself.

The amenities that are available,

I doubt very many people realize that there's a drugstore,

there's a shoe store, there's a Best Buy.

It really is a secret city.

[narrator] The daily operation of this unofficial city

are handled by a civilian administrator appointed by the Secretary of Defense,

a role insiders refer to as "the mayor."

[Dubois] When you have 23,000 people who come to work here every day,

probably another 3,000 to 5,000 visitors every day,

you are essentially managing a small city.

We have hospitals, clinics, restaurants.

We have a Pentagon conference center and library.

We have the Pentagon athletic center.

We have police force, a firefighting unit.

This is quite a complex organism, as all cities are.

[narrator] For those who work at the Pentagon,

the main entrance to the building is on the southeast side.

But for the military's top brass and the nation's leaders,

there are special VIP entrances.

[Dubois] We're at the Grand Ceremonial River Entrance to the Pentagon.

This is the entrance where the Secretary of Defense

goes to work every morning. That's his office up there.

This is where the President of the United States comes

when he visits the Pentagon, as well as other ministers of defense

and chiefs of defense staff from around the world

greeted in a parade on that parade field there.

Called the River Entrance because, of course,

there is the Potomac River.

This is the second ceremonial entrance of the Pentagon called the Mall Entrance.

It's the entrance for the Secretary of the Army

and the Secretary of the Navy, whose offices are behind me

on the third and fourth floors.

[narrator] With its five sides, five floors and five concentric rings,

the original plans for a military headquarters

were nearly scrapped in favor of something more traditional.

The five-sided shape of the Pentagon is an accident of history.

The initial spot that they'd chosen for the building

up near Memorial Bridge was five-sided.

It eventually ended up moving to a different spot of land

that was not five-sided.

So when they moved the building from the first site

to the second site,

they could have changed the five sides.

But the architects had come to realize

a five-sided shape worked better than a big rectangle.

[narrator] Although the Pentagon was first conceived

as a temporary structure,

were the original plans redrawn

and the design rapidly repurposed

for a more secret reason?

Why was the construction of the Pentagon begun

on September 11, 1941,

three months before the Japanese bombed Pearl Harbor?

Were the nation's leaders secretly preparing America for war?

A war that they knew was inevitable?

[Vogel] The War Department was scattered in 17 buildings

all around Washington.

It was horribly decentralized.

And General George C. Marshall, the army Chief of Staff,

gave orders to his chief of construction to come up with some sort of plan

that would allow them to consolidate this War Department.

President Roosevelt,

when he approved the plans for this huge building in secret,

had a vision of this building being used after the war as an archives

for all the paperwork that was filling up Washington.

- [siren wailing] - [narrator] December 7, 1941.

The Japanese bomb Pearl Harbor.

A date which will live in infamy.

[narrator] The United States goes to war,

and the pace of construction of the Pentagon picked up.

A centralized location for the War Department

now became a matter of national urgency and public pride.

At that point, they had about 4,000 people working on it up until Pearl Harbor.

When Pearl Harbor came, all stops were off.

We will gain the inevitable triumph, so help us God.

[applause]

[Goldberg] The sky was the limit at that point.

More people were added so that, at the peak,

it reached about 15,000 people.

The Pentagon was built in a race against time.

The architects and draftsmen

were, literally, sometimes just one step ahead of the pile drivers.

There was this incredible surge of patriotism and panic

to get this building ready.

[narrator] Completed in only 16 months,

the home of the War Department

has remained the central command post

of the U.S. Military for nearly 70 years.

[Dalessandro] We're standing in the center courtyard of the Pentagon.

Behind me, they erected a gazebo. And you can see it

in its present iteration. It's a snack bar.

And on top of that gazebo is a little owl.

When the people were here during the Cold War period,

and, actually, my service began in the Pentagon during that period,

this area quickly gained the nickname of Ground Zero.

People that worked in the Pentagon were convinced

that there was a nuclear bomb with its crosshairs

right on that owl at the gazebo.

So I have to tell you, as a young officer working here,

as I worked my way through the corridors,

sometimes I took a shortcut through the courtyard.

And I have to tell you, when I got to the center,

the hair on the back of my neck stood up.

I was sure that a nuclear round

was going to drop on me at any moment.

[narrator] But what military strategies and war games

are played out at a 21st century Pentagon?

Much of it is really an office building.

A lot of the work that goes on there is, you know, fairly routine, fairly mundane.

But a lot of the more secretive things, a lot of the planning,

a lot of the operational elements, intelligence analysis,

the high-level meetings, strategy,

all of that is going to be well out of public view.

But it is all happening right there.

[Rick Newman] Probably more than any place else in the United States,

the Pentagon is a clearinghouse

for every important decision that gets made in the U.S. military.

[narrator] As the home to America's military masterminds,

the Pentagon has also proven to be a five-sided target for terrorism.

[North] It's a target because it's the symbol

of American military power.

And that five-sided building does have

the home of the Department of Defense

and every senior service leader of the armed forces of the United States.

[narrator] September 11, 2001.

Al-Qaeda operatives execute a terrorist plot

to attack the U.S. using commercial aircraft as their weapons.

Their targets:

places of strategic economic,

political

and military importance.

[John Yates] On the morning of September 11,

I was just going around a normal day,

when about, I don't know, 9:15-ish or so,

one of my coworkers came over to me

and asked me if I knew what was going on in New York.

And so I said, "No."

She said, "Well, you have to come see."

We were watching what was going on in New York at that time,

so we knew something was going on.

[siren wailing]

[narrator] Amidst the chaos, American Airlines Flight 77,

which had taken off from Dulles International Airport

earlier that morning, had been hijacked over Ohio.

What those at the military headquarters could not predict

was that the Boeing 757 was heading straight for the Pentagon.

As it was getting close to the Pentagon, it actually did a 360.

So it flew basically over the Pentagon, flew around once,

and while it was doing that, it was descending.

[Jester] I just walked in the door to my office.

It was like a low rumbling noise for a few seconds.

And then the light fixtures in the room were just vibrating.

[narrator] At 9:37 a.m., the plane carrying six crew,

53 passengers and five hijackers

hit the Pentagon's western wall.

The aircraft tore through the Pentagon at an estimated 530 miles per hour.

With thousands of gallons of fuel onboard, it exploded on impact.

[siren wailing]

In an instant, the western side of the building was engulfed in flames.

[Yates] I'm standing there when there was just this tremendous explosion,

like nothing I'd ever heard before.

I remember a ball of fire coming from behind me and from my left

as it rolled across the ceiling.

And then there was just this-- this intense heat,

like nothing I've ever-- I've ever felt before.

And I had no idea what was going on.

[Dubois] This building shook.

This mammoth hunk of concrete and steel

absolutely shook with the impact of that airplane.

The plane was boring through three of the five rings.

It was just basically shredded by the concrete columns.

So you had thousands of gallons of fuel that were exploding

at the same time and sending fireballs down the hallway,

just blowing offices up.

[Yates] I remember being blown through the air,

and I didn't know where I landed. Didn't have a clue.

It's like somebody picked up the room and just shook it

like a dollhouse.

So I just started reaching out with my hands

'cause I can't see anything,

and everything I touched burned me.

Even the floor

was hot from the fire.

I just started crawling around, trying to find my way out.

[narrator] As firefighters battled to control the raging inferno,

rescue workers raced to find survivors amid the maze of rubble.

There were guys that went in, got blown over by a fireball

and got up burned, and went to drag people out.

There was a lady who was safe

and went back in to get people and got burned.

And she crawled out with people hanging on to her legs to get out.

There were people that saw people banging on glass

to try and get out and they went in to try to help them,

but there were insufficient tools, and they used their bare hands.

[Dubois] Secretary Rumsfeld

came all the way to the other side of the building,

much to the chagrin of his security detail,

and helped pick up litters and gurneys.

And it was

pretty extraordinary.

[Jester] It was one of the greatest sights in the world,

was watching the workers who had evacuated,

then go back to the building to rescue their fellow employees.

And, in many cases, they would just have to yell to them,

you know, "Follow my voice," because they couldn't see them.

And this voice said go out through this one particular door.

Which was at the far end of the room.

And I really wasn't sure where I was at the time,

but I just started crawling towards that voice.

And I knew I was going in the right direction

because the farther I crawled, the less hot it got.

So I just crawled until I ran headfirst into a wall,

and I just turned right and made my way

through all of the little aisleways and everything until I got out

into the corridor.

I was standing in the middle of five people,

and I'm the only one that walked out.

[siren wailing]

[narrator] Firefighters and emergency workers

battled heavy smoke and intense heat as they began the search

for the estimated 800 missing personnel who worked in the area.

[Newman] It was very difficult for this fire to vent

because of the unusual structure

of going into such a wide and such a low building.

The fire in many parts of the building, for hours,

was hotter than firefighting equipment is designed to handle.

Usually it's very easy to persuade people to leave a fire

and stay away from a fire, but at the Pentagon,

firefighters encountered lots of service members

who were determined to get back in.

They treated this like it was a war.

Had the fire commanders had their way,

they would have ordered everybody out

of the National Military Command Center,

but they got into a minor standoff with officers there who said,

"We're not leaving. The nation's under attack.

It is imperative to keep this part of the Pentagon operating."

So firefighters had to do something that they're not accustomed to doing,

which is putting out a fire in one part of the building

while keeping another part of the building operational.

[narrator] But just how perilous was the situation inside the building?

And what dangers did the destruction really pose to national security?

Only a few knew the true extent of the damage caused by the attack:

The Army General Staff Office as well as the Navy Command Center,

a critical intelligence facility,

were both completely obliterated by the fuselage.

The National Military Command Center was untouched,

but it was in jeopardy

as the blazing fire threatened to shut it down.

To make matters worse, a shift in the weather

would fuel the fire to an even greater threat.

[Kilsheimer] It was very windy,

and all of a sudden, I looked up

and I saw flames hooting out of the roof.

[Newman] The fire commanders started to rush crews

up to the top, up to the roof of the Pentagon.

So, they mounted a kind of an all-hands effort

to get that fire out on the roof,

because now this had become a national security issue to them.

[narrator] The fire was moving towards satellite

and computer equipment on the roof.

If it continued to spread,

the Pentagon would lose a vital communications link

to troops and commanders throughout the world.

But how could an attack such as 9/11

affect the Pentagon's top-secret military operations?

The National Military Command Center is a steel box,

in which you have all the sensitive communications

that reach around the globe.

And 24 by 7, 365 days a year, it is manned.

And from that command center,

the President of the United States will be receiving,

as does the Secretary of Defense,

the information with respect to the crisis of the moment,

and only the president

and the Secretary of Defense can push the button.

It needed to remain functioning

for the sake of keeping the U.S. military in operation,

and things like the cooling system in the Pentagon, the electrical system.

If the fire interfered with those things, the first thing it would do is,

it would shut down all the computers.

Without computers, there's no connectivity

and without communications, you can't run a military.

The building operations people realized

that they needed to keep water pressure in the building up

so that the fire department would be able to fight the fire.

Some of the building operation people

risked their lives to close off pipes

even as smoke was pouring down into some of those areas,

so that they could keep the command centers operating

despite the danger from the fire and smoke.

[narrator] With critical military missions underway around the world,

in the midst of the rescue efforts, the Pentagon's Security Service

was urgently retrieving top-secret information

now lying exposed in the wreckage.

But what vital military information were they trying to save?

The Security Service was trying to just basically retrieve all the safes

and filing cabinets that contain classified information.

Navy SEALs, for instance, said,

"Listen, we need to get back to our office

because we've got stuff in there that basically entails

how we operate, intelligence that our troops

have gathered out in the field, all sorts of things

that are essential to the functioning of the Navy SEALs,

and it's sitting up there in an office that nobody's guarding right now."

Firefighters who were in there

said they saw documents labeled top-secret

literally floating on wafts of smoky air.

[narrator] When the smoke cleared, 189 lives were lost

and hundreds injured.

Neither the Pentagon or the United States

would ever be the same.

September 12, 2001.

As the sun rose over the Pentagon

on the morning after the terrorist attack,

the first of many extraordinary events began to unfold.

The next day was a very unusual sight watching people coming

from the Pentagon City Metro Station, walking to work,

and the Pentagon is still on fire.

But people were coming to work.

[Dubois] Every person who worked here came to work.

This building was still burning.

This side of the building had collapsed.

Everyone came to work the next day.

[narrator] Forty eight hours after the impact,

firefighters finally got the blaze under control,

and the recovery effort could begin.

It took them a couple of days to get the roof fire under control.

Eventually they did.

It was a very hazardous, very difficult thing to do.

[narrator] Rows C, D and E of the area known as Wedge One

were destroyed by the impact and resulting fires.

But with an average daily work force of 25,000 people at the Pentagon,

how was it possible there weren't even more casualties?

The Pentagon was undergoing a renovation program,

and Wedge One was just being completed.

Had these planes hit a month either way,

there would have been a lot more people killed,

because there would have been a lot more people in the building.

[Vogel] Where the aircraft hit was the only part of the building

that had fire sprinklers throughout the section.

It was the only part of the building that had blast-resistant windows.

It was the only part of the building that had structural support.

It was the only part that had this Kevlar-type skin

that would protect against fragments of glass and stone.

[narrator] Overnight, the existing renovation work

turned to reconstruction.

But what was the secret behind the rapid rebuild of the Pentagon?

[Newman] It was considered a mission-critical thing

to get the Pentagon back online,

not to mention an extremely important symbolic act

to completely rebuild the Pentagon and make it better than it ever was.

[Vogel] The workers themselves came up with this plan

to restore the building by the first anniversary of the attacks.

So within one year, they would have the building back to its original state.

And they called it the Phoenix Project.

[Kilsheimer] It was a huge matter of pride

and patriotism for everybody there.

We had a total, at times, of 4,000 people working there.

The way the majority of those people felt was that we were going to show

people like these terrorists what Americans could do

when you came and did what they did to us.

A lot of people were working the whole 20 or 22 hours.

I would leave for two or three hours, I'd come back,

and there were guys sleeping on the floor

or the heliport on the concrete

so they could talk me as soon as I got back about things.

[narrator] But while working around the clock

helped speed up their schedule,

it was not enough to make their self-imposed, one-year deadline.

So what unconventional measures did they take

to finish even sooner than they had originally hoped?

[Kilsheimer] The first thing we did was tell everybody what to build that day

and follow it up with drawings, instead of doing drawings first.

There was one particular spot,

supposed to be a wall and then some pipes in the wall.

Well, the pipes were going first, the wall wasn't ready yet.

So the guys ran their pipes and they had to build the wall

around the pipes, which isn't the way it usually happens.

It's just everybody stepped out of box at all times.

[beeping]

[narrator] In addition to repairing the building,

new high-security safeguards were also constructed,

ones that would prevent or at least provide greater protection

for the Pentagon staff in case of a similar attack or worse.

[Dubois] We moved Route 110 further to the east.

We reinforced the west side of the building.

We got the berm over there and the blast wall.

Suffice it to say there are other defenses

that are now in place

that protect this building, and were a plane to enter

into restricted airspace and be determined to be hostile,

I don't think it would make it to this building.

[Newman] They certainly incorporated new security features into the building.

Many of those are not public and they shouldn't be public,

because they could give future terrorists ideas

about how to attack the Pentagon again.

What you can see at the Pentagon is the direct affect

of what happened on 9/11/01,

and the reality that there are people, bad people,

who would do great damage if they could.

[narrator] Inside the Pentagon,

reconstruction also extended to other areas of the building.

- [elevator bell dings] -Areas hidden from the public.

and built according to top-secret specifications.

[Sajeel Ahmed] There are a number of areas

which need to support the mission itself,

including the operation centers and the regular tenant spaces itself.

That's all I can go there.

[Clark] We don't always know about those.

And if we knew about them,

we probably couldn't tell you everything about them.

[narrator] Wedge One renovations

covered an area of one million square feet of space.

Building improvements included blast-resistant windows

and a new communications infrastructure.

The Phoenix Project finished one month ahead of schedule.

A fitting end to what is globally considered

to be the most incredible reconstruction project in history.

[Kilsheimer] We actually rebuilt the building

and had butts in chairs on September 11, 2002.

I don't think there's a person that worked on that site

that wouldn't say that was the most important thing

in at least their construction life.

The Pentagon Memorial: We claim this ground

in remembrance of the events of September 11, 2001.

The steps directly behind me are where the impact took place.

And, of course, the blackened limestone block,

now etched with that fateful day, put into place after Project Phoenix

concluded one year to the day later, September 11, 2002.

[narrator] In the wake of the 9/11 attack,

improved security was initiated to both the physical structure

and the surrounding area of the Pentagon.

But within the walls of the military compound,

security measures were also upgraded.

- [police radio chatter] - [Harris] Prior to 9/11, the Pentagon

did have essentially a police force, a security guard force, if you like.

After 9/11, that group became a new unit,

the Pentagon Force Protection Agency.

[Newman] The Pentagon Force Protection Agency,

otherwise known as the Pentagon police, are an annoyance

to everybody who works there, because they make it hard to get in.

If your badge is not in order, they won't let you in.

But they're extremely important to keeping the Pentagon secure.

The Pentagon uses the most up-to-date technology

in terms of access control systems.

All the different technologies are constantly changing.

They've gone to retina scan, hand geometry scans,

to all kinds of devices.

[narrator] The Pentagon Force Protection Agency

is tasked with being an all-threats agency.

In addition to security,

the agency is trained to handle chemical,

biological, radiological

and even nuclear threats.

I developed a motto which is

"We Protect Those Who Protect Our Nation,"

It makes the organization feel that we're doing our part

in the overall mission of the Department of Defense.

[narrator] But beyond the threat of another physical attack,

the Pentagon must maintain the highest level of security

to protect the nation's greatest secret-keepers,

who work deep inside the compound.

Some of the country's most sensitive secrets, as you can understand,

are held within this building.

And in some cases they're held within certain minds.

[Harris] The Defense Intelligence Agency, DIA,

is one of the other, sort of primary, the big intelligence agencies

within the intelligence community.

And it's really focused on missions pertaining

to the Defense Department's business, so, fighting war.

[explosion]

And, really, in the past ten years, particularly in Iraq and Afghanistan,

DIA has been the place to produce or to handle the intelligence

that goes out to soldiers in the field.

[narrator] But the DIA is not the only information-gathering agency

housed at the Pentagon.

The biggest and most covert intelligence unit,

the National Security Agency,

also operates within the military headquarters.

[Harris] National Security Agency, or the NSA,

is the government's eavesdropper.

It collects what's called signals intelligence,

which means phone calls, fax transmissions,

e-mails, text messages.

If it goes over a wire, or over a wavelength in the air,

NSA grabs it.

They have a global system for electronic intelligence collection

that includes satellites,

wire taps,

monitoring of Internet networks.

Their job is if it's electronic, if it's data and it's moving around,

they grab it.

If I had to put money on which agency has the most secrets,

I would say it's the NSA.

The NSA is certainly collecting the most information.

[narrator] But when secret information must be shared inside the Pentagon,

what special protocols are put into action?

And how is sensitive information stored inside the Pentagon kept safe,

and accessed only on a need to know basis?

Paper documents are transferred by hand

by a cleared person, in some cases, inside a locked briefcase.

[Yates] In a building where 23,000 people work,

there are a lot of secret documents.

And part of my job is to keep those documents safe and secure,

and out of the hands of people that would do our nation harm.

There's different classifications for different types of information.

And based upon your need to know

and your background investigation level, you get access.

Your duties require you to have access

in order to get it accomplished.

There are levels of classified documents

from "for official use only" all the way up to "top secret"

SCI clearances,

Special Compartmentalized Intelligence.

[narrator] Conversations about classified information

are strictly forbidden in the Pentagon.

But there is one place that the military's ultimate top secrets

can be discussed openly.

In the steel box offices known as SCIFs.

There are lots and lots of classified spaces inside the Pentagon.

Some of them are known as

Sensitive Compartmented Information Facilities.

The acronym for that is SCIF.

They're not just places with limited access,

where people are cleared to discuss classified information.

They're actually hardened against electronic eavesdropping.

So there might be wire structure built around those cages.

There might be materials in there

that are intended to defeat any kind of electronic eavesdropping,

particularly audio devices that somebody could point at the Pentagon.

[narrator] Even the disposing of classified documents

leaves little room for secret information to fall into the wrong hands.

[Yates] A burn bag is a specially marked brown paper bag

that classified material,

or even sensitive, unclassified material. is put into.

And then every day they have pickup here at the building,

it's put into the back of a van,

it's taken out to the incinerator plant that they have here,

and it's burned.

[narrator] Information is power in the intelligence community,

and secrets are the most valuable kind of information.

But what kinds of secrets

are the Pentagon's best military minds ultimately trying to find?

I think what they're really after in the intelligence world

is anything that can tell them about what's going to happen next.

It's used in a way almost like a crystal ball.

You look to data to almost see the future.

[narrator] In July of 2011,

the Department of Defense released its first official strategy

for operating in the digital age.

Traditionally tasked with keeping America safe by land,

air and sea, the Pentagon is now taking steps to investigate,

eliminate and annihilate threats from cyberspace.

[North] The Pentagon has not only been the target of physical attacks;

it's also been the target of hundreds of cyber attacks

on a day-to-day basis.

It is target number one for adversaries

who want to try to penetrate our communications,

our computers, our hardware, software and literally shut down

the national security apparatus of the United States.

We are already experiencing our 9/11 in cyberspace.

It's already happening.

We've lost trillions of dollars over the last two years

of intellectual property.

The hard thing about cyber security

is you don't know that the asset's gone.

If someone takes your data, you're still using your data.

If someone takes your submarine,

you know the submarine's gone.

[narrator] The most significant breach

of U.S. Military networks occurred in 2008

when a foreign intelligence agent inserted an infected flash drive

into one of the government's laptops in the Middle East.

The malicious code spread undetected through classified systems,

uploaded itself onto a network run by the U.S. Central Command

and put its servers under enemy control.

What we found in 2008 is that attacks can be launched

even when an agency or a department

is offline and not on the Internet.

It can happen through malicious software being carried

from one place to another and inserted onto an offline network

using such technology as a USB drive.

This is really analogous to, in the old days of the Cold War,

you would send a spy into a government facility,

posing as a visitor,

who would then try and physically steal the documents.

[narrator] Cyber Command is the official unit

tasked with protecting the country's digital infrastructure

in the 21st century.

While its mission is to protect military assets,

has Cyber Command already launched

any counterattacks of its own?

We saw something very interesting happen in Iran

recently with this so-called Stuxnet virus.

This apparently was a virus that was able to effectively shut down

the nuclear program there, and by some estimates,

set it back by one to three years.

That is a profound capability if we do, in fact, have that capability.

[narrator] But who are the secret stalkers

plotting to hack the servers and systems at the Pentagon?

[Newman] I think it's widely believed that the Chinese,

the Russians, perhaps even some of our allies,

pay very close attention to the Pentagon all the time.

[Harris] If you look at the people who are trying to get

into military networks, it's going to be everyone from foreign spies

to potentially even corporations

who are trying to get information on their competitors.

But increasingly what the Pentagon is really most worried about

are other governments, militaries, foreign spies,

particularly in China, which has been the source

of many of the attempted intrusions and some of the successful ones.

And also in Russia, where the intelligence services

are still very much interested in what we are doing in our military.

[Ryan] If the Internet is anonymous,

that means the attackers have the full scope of the cyberspace

to be able to launch an attack

without being known who they actually are.

So that's one of the big challenges that we need to solve,

is know who the attacker is.

[narrator] As long as America has enemies wishing to do it harm,

the Pentagon will be a tempting target for a cyber or physical attack.

[Harris] It is a giant building.

It's very difficult to protect, as 9/11 proved.

The military has put, at various locations around Washington,

portable missile batteries that are there in case

someone were to try and fly a plane into the Pentagon or another building.

[narrator] While the Pentagon

is the central headquarters to the U.S. military,

are there secret outposts that allow the armed forces

to operate outside the Washington compound?

There are secure, undisclosed locations

that are in various places that I will not tell you where they are.

[narrator] Some believe there is a secret facility

built into the side of a mountain in Raven Rock, Pennsylvania,

known as Site R.

Might this, in fact, be a top secret location

of a second Pentagon?

It's a very sophisticated, big cave that is built into the side of a mountain.

And this is the place where, in the event of a nuclear war,

our country's leaders were supposed to go

and continue running the country, regardless of what had happened.

It is designed to withstand a nuclear blast.

What you have inside are all of the communications systems

that you need, that the president and the defense secretary

would need to give orders to the military.

The ability to launch the strategic nuclear arsenal,

if necessary.

[narrator] For seven decades,

the Pentagon has been an icon of American strength

and military excellence.

But for those who know the structure best,

the secret to its national importance

extends far beyond the building itself.

The most extraordinary aspect of this building is not the concrete.

It's not the limestone.

It's not the 17 and a half miles of corridors.

It's the 23,000 people who come to work here every day.

They are the most special part of this building.

[Harris] This is where all of the thinking about the future

of what threats look like occurs.

There probably is no more greater collection of secrets

than what you have within those five walls,

because, truly, it is all about the preservation

of the national security of the United States.

When people go to bed at nighttime and go to sleep,

the Pentagon is always working.

There's people there who are watching

what is going on around the world,

making sure our country is safe.

[narrator] While their methods may be covert,

the men and women who work at the Pentagon every day

are dedicated to the building's core mission:

to defend and protect the United States

from those who would do America harm.