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(This program is no longer available for online streaming.) On September 11, 2001, an unimaginable horror unfolded that devastated a nation and the world. Fifteen years later, we are still gripped by terror, but it has transformed. The attacks have been coming fast and furious—to Boston, Paris, Brussels, San Bernardino, Orlando, Nice—but they are no longer commanded by a central entity. This is terrorism in the age of the Internet: crowd-sourced violence.In this special report, NOVA traces the evolution of terror strategies from the World Trade Center to today. How have radical organizations grown to make use of modern propaganda and social media tools in order to cultivate an army of self-radicalized killers? What is going on inside the minds of this new breed of terrorist? What new techniques and technologies can help law enforcement cope with this elusive threat? And how can psychology and technology be leveraged to end this dreadful cycle of terror?

From 9/11 to today’s crowd-sourced violence, trace how terrorists’ strategies have evolved.

15 Years of Terror

Alcatraz Island still draws tourists for its history as a federal penitentiary. But it also has a rich past as little-known military base, erected to guard against foreign invasion. Image Credit: MBPROJEKT_Maciej_Bledowski, iStock

Using non-invasive techniques, archaeologists have confirmed the presence of a coastal fortification beneath what was once the prison’s recreation yard.

Ground-Penetrating Radar Reveals Military Structures Buried Beneath Alcatraz Penitentiary

<div class="rich-text">Churchill launches the largest military evacuation in military history. But there's a secret killer in the waters.
 
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<div class="rich-text">Churchill launches the largest military evacuation in military history. But there's a secret killer in the waters. 
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Hitler’s Secret Weapon

How Deadly Was the Musket?

A team of experts put an 18th-century musket to the test — revealing how deadly it really was.
At Fort Ticonderoga, a centuries-old weapon is put through a modern test. Using ballistic gel, a slow-motion camera and a chronograph, experts investigate the true power of the British “Brown Bess” musket.
How Deadly Was the Musket?Published: April 17, 2025Narrator: Today, the musket is seen as crude and inaccurate, especially when compared to modern guns. But is that true? At Fort Ticonderoga in Upstate New York, historic firearms researcher, Joel Bohy, is finding out how effective the musket was on the battlefield.Joel Bohy: So, what we&#x27;ve got here is a British Pattern 1756 Long Land musket, more commonly known as the Brown Bess. The Brown Bess begins use in about 1730, and this type of gun would&#x27;ve been the workhorse of the British army through the 18th century into the 19th century. It was an extremely important gun to building the British Empire and used through the American Revolution.Narrator: But for Joel, the best way to assess the musket is not by comparing it to modern weapons, but by testing its effectiveness in battle 250 years ago. To gain a better understanding, Joel&#x27;s team will fire at a ballistic gelatin block designed to replicate human tissue, providing valuable insight into how different projectiles can affect a person&#x27;s body. With the aid of a slow motion camera, he&#x27;ll also try to answer a question, how damaging could a musket shot be? Finally, he will measure the speed each round exits the barrel, known as the muzzle velocity, using a chronograph. Marksman Jay Waller will be firing the guns. First up, the musket with the 0.69 caliber ball. Pulling the trigger instantly sets off a chain reaction in the flintlock mechanism. A stone flint strikes a steel hammer. The impact creates sparks, which ignites the priming powder in the pan. This ignition passes through a small hole and sets off the gunpowder inside the barrel. The gas pressure produced here propels the round out of the gun. On inspection, it&#x27;s a direct hit.Joel Bohy: You can see where it traveled right through the block and came out the other side.Narrator: Reviewing the footage, they can see the horrific damage caused.Joel Bohy: Wow. You see that ball zip right through. Look at the cavitation in the gel from that .69 caliber ball.Narrator: When the ball moves through the block, it displaces the gel around it, creating a cavity. This is known as cavitation, similar to what would happen to living human tissue, devastating to bones and internal organs.Joel Bohy: The men on Lexington Green knew how deadly these weapons were, but they never had the opportunity to see the damage in the way that we&#x27;re seeing it now. Wow. Wow.Jay Waller: Yeah, certainly gives a whole different appreciation and horror for what happened.Narrator: The musket is clearly deadly. So why do we see it as a primitive weapon? Likely, because of what later guns can do. Joel demonstrates this with the modern rifle.Joel Bohy: Oh! Whoa! Look at that. You can see the smoke from the bullet.Narrator: The modern rifle&#x27;s power is far more terrifying. But what does the data reveal? Using the chronograph, Joel and Jay compare muzzle velocities.Joel Bohy: On the Endfield, that is 2,314 feet per second, whereas the musket is 845 feet per second. So there&#x27;s a big difference between the two guns. But you can really see the velocity when you look at the ballistics gelatin blocks.Narrator: The higher velocity of the modern rifle&#x27;s bullet means it carries substantially more energy. When it penetrates the block, much of this is transferred to the gel, causing it to lift into the air.

A team of experts put an 18th-century musket to the test — revealing how deadly it really was.

The World’s First Combat Submarine

Its nickname was the “Turtle”.
During the American Revolution, an American inventor developed an underwater vessel that could destroy British ships by attaching a bomb to the hull of a ship. These are some of its unique features.
The World’s First Combat SubmarinePublished: April 17, 2025MIKE LOADES: This is a model of the first combat submarine. Now I say model because the original doesn&#x27;t exist. All we have is a few hints and clues from subsequent writings.NARRATOR: The writings come from American inventor David Bushnell.DAVID BUSHNELL: The external shape of the submarine vessel bore some resemblance to two upper tortoise shells of equal size, joined together.NARRATOR: It was later nicknamed the Turtle.MIKE LOADES: First, you&#x27;ve got the overall shape. It&#x27;s using the technology of a barrel. It&#x27;s thick oak staves, bound together with iron hoops. It&#x27;s not quite barrel shaped though. And the reason for that is because you need space inside for an operator to sit. So that&#x27;s going to broaden it in the middle. And you need space at the top for a hatch for the operator to get in.At first glance, it immediately reminds you of a space capsule. But what it is, in fact, is a time capsule, a time capsule of contemporary technologies. You&#x27;ve got these pedals here, so the operator is pedaling away. This is powered by pedal power, and they are driving a propeller.NARRATOR: The concept of the propeller dates back to Greek mathematician Archimedes. His Archimedes screw famously moved water using a spiral blade inside a tube. Bushnell took this concept and located a blade on the outside of his turtle. This is thought to be one of the first practical applications of a propeller, along with a rudder. The turtle has all the components needed to maneuver on the surface.MIKE LOADES: A particular feature on the outside of the vessel is this hatch at the top here. It&#x27;s got these water tight windows, so he has got some natural light inside. Then above that, these strange looking things are really snorkels, so that when it&#x27;s above water, it&#x27;s fully ventilated.NARRATOR: Using the windows, the operator could maneuver on the surface to locate and position the turtle next to a ship. It is then ready to descend by filling the area at the base of the vessel, known as the bilges. To do that, the operator kicks a lever.MIKE LOADES: This will flood the bilges down there with water.NARRATOR: Under the surface, a second propeller is used to lower or raise the turtle. Once submerged in darkness, the operator has only two instruments for guidanceMIKE LOADES: This is a barometer. It has a little cork in it, and each of these marks on the glass tube represents a fathom that&#x27;s about six feet. So as he sees the cork bobbing down, he knows he&#x27;s going down another six feet. How can you see that underwater? Because it&#x27;s been covered with a fungus called foxfire, which is luminous, it glows in the dark.And over here is a compass, which again, the needle on the compass has been coated with this luminous fungus so he can read his heading.NARRATOR: The turtle is designed to move into position. Armed with a bomb to blow up its target.MIKE LOADES: So, assuming that we&#x27;ve now got to the right that we now need to attach the payload. And that&#x27;s this crank here, this crank operates that drill at the top and that bores its way up into the hull of a ship.NARRATOR: The drill is attached to the bomb by a rope. Once connected, the turtle detaches itself, leaving the explosives secured to the ship.MIKE LOADES: And now you&#x27;ve got to get out of here. So you you pedal away when you want to surface, you use these two hand pumps, yet more exertion to save your life. Pumping away to get that water out of the bilges. But my goodness, that&#x27;s a heck of a lot of work to get to that stage.NARRATOR: Employed to carry out this dangerous mission, 27 year old American Ezra Lee. The plan: drive into New York Harbor and blow up the British flagship HMS Eagle. But how could Ezra Lee attach a bomb big enough to sink the British ship and get away safely? Inventor David Bushnell&#x27;s writings provide some clues, allowing pyrotechnics expert John Hargreaves to figure out how it was supposed to happen.JOHN HARGREAVES: I&#x27;ve rigged this as a demonstration. This is pretty much the size of the bomb that would have been on the turtle.MIKE LOADES: That holds the gunpowder?JOHN HARGREAVES: Correct, 150 pounds.MIKE LOADES: How do we get a spark to it?JOHN HARGREAVES: Well, in the references to Bushnell&#x27;s machine, they show a flintlock mechanism.MIKE LOADES: So this little pocket pistol?JOHN HARGREAVES: Correct.MIKE LOADES: Which has got this flint lock here so that flint strikes that which creates the spark.NARRATOR: The pistols’ muzzle is screwed into the barrel. When it&#x27;s fired, it will ignite the gunpowder. But Ezra Lee would need time to escape before it exploded. Bushnell had a plan.DAVID BUSHNELL: Within the magazine was an apparatus constructed to run any proposed length of time under 12 hours.JOHN HARGREAVES: This is a specialist clock. It is a very early 19th century version, actually, but it is the nearest thing I can find to the right mechanism.NARRATOR: The mechanism John thinks Bushnell used comes from a period pocket watch.JOHN HARGREAVES: The pocket watch had been around the beginning of the 17th century. It was a pretty rare thing. And they were all watches like this. The clock is going to count down to zero when it gets to zero. It pulls a lever which I have attached to the trigger mechanism of my pistol, so it pulls the trigger and fires the gun.MIKE LOADES: This is absolutely ingenious, John.JOHN HARGREAVES: I&#x27;m going to set it to a minute to. Can you hear it ticking?MIKE LOADES: We have a ticking bomb.JOHN HARGREAVES: This is ticking.MIKE LOADES: Oh, look at that. Excellent. Proof of concept.JOHN HARGREAVES: Yes.NARRATOR: The timer for the bomb was set to 30 minutes and sealed in a watertight casing. The countdown would begin when the bomb detached from the turtle.DAVID BUSHNELL: This apparatus could not possibly move till by casting off the magazine from the vessel it was set in motion.NARRATOR: The firing mechanism works on land. But will the bomb explode underwater? When Bushnell first tested the bomb, he did so with varying amounts of gunpowder. For safety, John is only using 5 pounds. Ezra Lee was carrying 150.At 11 p.m. on September 6th, 1776, after being launched into the water from a whale boat, Lee starts his mission.Even though this was a scaled down test. John is taking all the necessary precautions. As Raleigh is facing the real risk that the bomb could fail to detonate or worse, explode too early, killing him instantly. For over two exhausting hours, with the constant risk of being spotted, he navigates toward the British ship. Upon reaching it, he begins his descent, dropping close to 30ft below the surface with the bomb.MIKE LOADES: Oh! Yeah, she blows.That&#x27;s just 5 pounds?JOHN HARGREAVES: Yes, 5 pounds of gunpowder.MIKE LOADES: The bomb they&#x27;re dealing with was 30 times that magnitude.NARRATOR: A detonation that large would have been catastrophic. The wooden hull of a ship offers less resistance to the bomb&#x27;s explosive force. And the denser water around it.MIKE LOADES: It would have just ripped through the bottom of the boat. Instant destruction in.NARRATOR: But HMS Eagle is not blown up. After making his descent as Ezra Lee is unable to attach the bomb.DAVID BUSHNELL: He went under the ship and attempted to fix the wooden screw, but struck, as he supposes, a bar of iron.NARRATOR: At this crucial moment, running out of air, he abandons the mission. In a later attempt, the boat carrying the sub is sunk by British gunfire. This is the end of the turtle.MIKE LOADES: I have absolutely no doubt that if it had been successful and if it had been repeatable to scale, if they built many more turtles and they had destroyed the British fleet, it would have shortened the war by years. The war would have been over in months.

Its nickname was the “Turtle”.

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Revolutionary War Weapons

Explore key military technologies in the American colonies’ fight for freedom.

Area 51: UFO Sightings and an Infamous Government Cover-Up

Area 51’s UFO myths became a cover for secret testing of cutting-edge military technology.
For decades, rumors of alien spacecraft at Area 51 have captivated the public imagination. In what is now known as one of the most infamous government cover-ups, an absence of information fueled wild speculation. Discover how UFO stories may have served as a convenient smokescreen for secret testing of advanced military technology.
Area 51: UFO Sightings and an Infamous Government Cover-UpPublished: January 24, 2025Narrator: When it comes to government cover-ups, perhaps the most infamous is Area 51. Tales of alien spacecraft hidden inside this remote Air Force base about 83 miles northwest of Las Vegas have persisted for decades. It turns out the military has been secretly developing cutting-edge technology here since the 1950s but did not even acknowledge the existence of the base until 2013.Alex Hollings: There are lots of aircraft we know have been tested at Area 51, entirely in secret at the time, including the F-117, the SR-71, the B-2 Spirit, and many more.Right around the same time the B-2 Spirit was in development, common sightings of UFOs around the United States tended to transition away from the pie saucer shape we were familiar with in earlier decades and toward a more triangular shape. This is a model of what people claim was the TR-3B, which is a legendary aircraft that people allege was built using reverse engineered alien technology.Narrator: By the 1990s, rumors of triangular-shaped spacecraft became so widespread they became part of popular culture. Blockbusters like the X-Files featured a triangular-shaped alien spacecraft hovering over Agent Fox Mulder&#x27;s head.Alex Hollings: I think the government should and does expect that the public is going to fill in the blanks as they see fit. As long as people are talking about aliens operating out of Area 51, well then they&#x27;re not revealing anything about the legitimate military platforms that are being tested there. It creates a bit of a smoke screen.Hakeem Oluseyi: There&#x27;s always advanced technological programs going on that are on a need-to-know basis. If you don&#x27;t need to know, even if you are a member of the government or the military, you&#x27;re not going to know. And that&#x27;s the way it should be.Sean Kirkparick: This is all about spy versus spy or military versus military to maintain technical superiority. We don&#x27;t want other people to learn what we&#x27;re building, where we might employ it, because then they can defeat it. There are reasons to do that. None of it is alien. None of it.

Area 51’s UFO myths became a cover for secret testing of cutting-edge military technology.

Is the Government Hiding Information on UFOs?

What does the government know about UFOs? Experts weigh in on the need to identify these objects.
The government does keep secrets about aerospace technology, but are those linked to UFO sightings? How much do they really know? With growing concerns about national security and more citizen sightings of unidentified objects in our airspace, the need to identify these unknown objects is greater than ever before.
Is the Government Hiding Information on UFOs?Published: January 24, 2025Alex Hollings: I can tell you, unequivocally, that the government does keep secrets when it comes to aerospace technology. The Pentagon has what we often call a black budget, which can sometimes exceed $65 billion in a year.Alejandro Rojas: Even within the military, there&#x27;s never been a consensus, really, that it&#x27;s this or that, or that it&#x27;s not extraterrestrial.Sean Kirkpatrick: We cannot rule out extraterrestrials, but you have no evidence for it. It comes back to the evidence.Hakeem Oluseyi: Regular citizens have been reporting things for decades, and yet we hear nothing from the government about what this may be.Shelley Wright: And now that we have more observations, more cameras, more cell phones that are taking pictures of phenomenon in our atmosphere, scientists need to come forward and talk about how we can identify these objects.

What does the government know about UFOs? Experts weigh in on the need to identify these objects.

Alcatraz might be best known as a popular tourist destination, the site of the former high-security prison that once held Al Capone. But a team of archaeologists has now unveiled new evidence of this San Francisco Bay island’s often overlooked military history.In the <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/nsg.12031">study</a>, published last Thursday in the journal Near Surface Geophysics, researchers used non-invasive technologies to pull back the curtain on a stunningly well-preserved 19th century coastal fortification that lies beneath the ruins of this infamous federal penitentiary. The work confirms that while prison construction in the early 1900s destroyed much of the former military installation, several structures were buried more or less intact, enshrining a critical sliver of Alcatraz’s colorful past.
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“This really changes the picture of things,” says study author <a href="https://www.binghamton.edu/anthropology/faculty/postdoctoral.html">Timothy de Smet</a>, an archaeologist at Binghamton University. “These remains are so well preserved, and so close to the surface. They weren’t erased from the island—they’re right beneath your feet.”
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<figcaption>Study author Timothy de Smet used non-invasive techniques to create a subsurface map of remains of Alcatraz Island's former military fortification. Image Credit: Timothy de Smet, Binghampton University
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Prior to the mid-1800s, Alcatraz Island was a barren strip of land capable of supporting little more than a raucous population of seabirds. But in the wake of the California Gold Rush, the United States government looked to the rocky outcrop as a potential military base to protect the newly bustling city from foreign invasion. Over the next several decades, a stone- and brick-based fortification was erected, then rebuilt as earthen structures better equipped to handle erosion. But Alcatraz struggled to keep pace with the rapid changes in artillery during and after the Civil War era, and by the late 1800s, the island’s defenses were essentially obsolete. Military pursuits on Alcatraz were abandoned shortly thereafter.
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When the island’s prison was erected around the turn of the 20th century, little physical evidence of its former architecture remained—or so many thought. The new study, led by de Smet, says otherwise. To look beneath the surface, the researchers deployed ground-penetrating radar, which pulses electromagnetic waves into the earth, returning signals that can visualize remains without excavation. The strategy uncovered a labyrinth of subterranean structures, including an earthwork traverse, a kind of defensive trench, running beneath the penitentiary’s former recreation yard.“This really reinforces what several historians and archaeologists had long suspected,” says study author and Alcatraz historian <a href="http://www.johnamartini.com/">John Martini</a>. “Up until this point, we had nothing to go on except for a few visible trace remains and maps—and a lot of suspicion.”In a way, Martini says, the findings reflect just how limited real estate was on Alcatraz, which clocks in at less than 50 acres. “On a small island, there’s only so many places you can build,” he says. “And it’s unlikely they went to the trouble of demolishing all this stuff.”
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<figcaption>A 15-inch Rodman cannon and its gun crew, 1869. These were the largest guns mounted on Alcatraz. Image Credit: National Park Service, Golden Gate National Recreation Area
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Because they’re both sensitive and non-destructive, techniques like ground-penetrating radar are crucial for these kinds of investigations, and can complement historical records that survived the era, says <a href="http://jolenebabyakauthor.com/">Jolene Babyak</a>, an Alcatraz historian who was not involved in the study.With these results in hand, de Smet and his colleagues plan to continue archaeological investigations under Alcatraz. Going forward, only time will tell what this rock will reveal, Martini says. “Below the surface, Alcatraz is still full of mysteries,” he says. “There’s still a whole lot to be learned.”
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<figcaption>Soldiers posing in the island’s ordnance yard. A brick Citadel capped the summit of Alcatraz. 1869. Image Credit: National Park Service, Golden Gate National Recreation Area
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Identifying Lost Crew with Forensics and DNA Analysis

Can a team of forensic archaeologists identify three WWII airmen that disappeared?
In 1944, three WWII airmen disappeared beneath the waves. Now, there may be hope for the return of their remains. The Department of Defense, which operates the largest forensic anthropology lab in the world, does a skeletal analysis to figure out if the recovered remains belong to more than one individual. Then the Armed Forces Medical Examiner System takes over to conduct a DNA analysis using family samples.
Identifying Lost Crew with Forensics and DNA AnalysisPublished: December 3, 2018Onscreen: Dec 17, 1944: A B-24 bomber was shot down off Croatia. Three airmen disappeared beneath the waves: Pilot Eugene Ford, Navigator Russel C. Landry, and Flight Engineer Charles E. Priest.Now, there may be hope for the return of their remains. The Department of Defense operates the largest forensic anthropology lab in the world.Tyler Dunn: It’s my job to do a skeletal analysis blind, so I don’t bias myself.We were presented with 11 teeth; a right humerus, that’s relatively intact compared to everything else; a fragment of a vertebra; a handful of, sort of, non-diagnostic long bone fragments—we can more or less just tell that they’re bone; some fingers, a bit of a toe, and then most of the lower right leg, so a tibia and a fibula.The first question I generally ask is the minimum number of individuals. So, we try and figure out if this could be, or is, more than one person.Based on this case, the skeletal—it’s called M.N.I. or &quot;minimum number of individuals&quot; — the skeletal M.N.I. is one. I have good reason to think that this is one individual.Onscreen: This conclusion is backed up by the dental analysis.Dunn: So, I can tell that this is all teeth from one individual, based on tooth shape, the size of the tooth, and more or less what they look like.Onscreen: It appears that only a single airman was recovered, based on the skeletal evidence. But who was it?Dunn: We more or less measure how long the tibia is. The stature for this individual that we estimated was right around 5 foot 10.Onscreen: Yet the skeletal remains alone cannot provide a definitive ID, so they turn to DNA. The Armed Forces Medical Examiner System now takes over.Timothy McMahon: This is where we take the unknown and we put a name to them.Onscreen: First they extract DNA from the bones and teeth and then sequence many different regions. Then they compare the sequence against family reference samples until finally a match is confirmed.Seven months later…Jim Bell: …so, based on that, the laboratory analysis, established remains of those as First Lieutenant Eugene Ford, serial number Oscar 805804, U.S. Army Air Forces.

Can a team of forensic archaeologists identify three WWII airmen that disappeared?

Topic: Military & Espionage

Hero Feature

15 Years of Terror

Featured Content: Military & Espionage

Ground-Penetrating Radar Reveals Military Structures Buried Beneath Alcatraz Penitentiary

Hitler’s Secret Weapon

Explore Topic: Military & Espionage

How Deadly Was the Musket?

The World’s First Combat Submarine

Revolutionary War Weapons

Area 51: UFO Sightings and an Infamous Government Cover-Up

Is the Government Hiding Information on UFOs?

Ground-Penetrating Radar Reveals Military Structures Buried Beneath Alcatraz Penitentiary

Identifying Lost Crew with Forensics and DNA Analysis