Nazi Attack on America

A sunken German U-boat off the coast of New Orleans tells the story of Operation Drumbeat. Airing May 6, 2015 at 9 pm on PBS Aired May 6, 2015 on PBS

Program Description

Long before 9/11, a far deadlier, little-known attack from the ocean depths struck our shores, lasting three-and-a-half years and claiming 5,000 lives. Now, famed undersea explorer Bob Ballard, discoverer of the Titanic, investigates the wreck of one of the attack craft, a German submarine that lies at the bottom of the gulf just a few miles off New Orleans. U-166 was part of Operation Drumbeat, a highly successful U-boat operation that caught East Coast cities and shipping almost completely unprepared. With state-of-the-art survey gear Ballard probes the wreck and explores a dramatic mystery in the official story of the sub’s sinking.

Transcript

Nazi Attack on America

PBS Airdate: May 6, 2015

NARRATOR: January, 1942: America is just weeks into World War II, when the European fight comes to our shores. Hitler's U-boats waste no time going on the attack.

ROBERT (BOB) BALLARD (President, Ocean Exploration Trust): They brought the war to us, in a way that caught us by surprise.

NARRATOR: The attacks are devastating: thousands of lives lost, more ships sunk than at Pearl Harbor, and Nazi spies secretly delivered to American soil.

MARTIN K. A. MORGAN (World War II Historian): They kicked our asses, and yet, we were getting no payback.

TIM MULLIGAN (Author, Neither Sharks Nor Wolves): A lot of Americans have forgotten how close the war came to our shores, and how close it was to our homes.

NARRATOR: Now, renowned explorer Robert Ballard and his team are returning to this forgotten battlefield with the latest technology.

BOB BALLARD: Okay, team, a hundred meters.

Here, we're able to get a picture that shows you what it would be like if you could take the water away.

NARRATOR: Their work will help rewrite this chapter of World War II and bring closure to a 73-year-old mystery: Who sank German U-boat U-166?

How close did the Nazis come to victory in the Atlantic? Right now, on this NOVA/National Geographic special.

The Gulf of Mexico, 120 miles off the coast of New Orleans: these peaceful waters were once the setting for a violent, little known chapter of World War II. Deep below the surface, lie the remnants of a devastating Nazi attack on America, “Operation Drumbeat.”

Just after the U.S. entered World War II, Hitler's submarines, the deadly U-boats, struck hard and fast, up and down the east coast. They hunted down and sank the vulnerable cargo ships that were critical to the Allied war effort. And they took the war further, extending their assault all the way into the Gulf of Mexico.

Now, explorer Robert Ballard and his crew prepare to investigate this battlefield. To reach the sea floor, they'll use high-tech remotely operated vehicles, “R.O.V.s.”

BOB BALLARD: The beauty of the R.O.V.s: these vehicles can stay down for days and days and days.

Square up on the target and drive over to it.

NARRATOR: The R.O.V.s descend one mile beneath the surface, where the casualties of the Nazi assault still rest. A World War II-era cargo ship, the Alcoa Puritan: in 1942, she hauled aluminum ore, vital to America's wartime factories. Her scars are still vivid.

BOB BALLARD: That's a, that's a hole. That's a shell hole. So, if you could, stop laterally and go in and frame that.

RICHIE KOHLER (Wreck Diver): These are bent inward.

BOB BALLARD: Yeah. It's funny. You can tell it went in.

RICHIE KOHLER: Yep.

BOB BALLARD: It's funny how…

NARRATOR: Joining Ballard is wreck-diver Richie Kohler. He's spent decades studying and diving on sunken U-boats.

RICHIE KOHLER: This wreck is a snapshot of when the U-boats first came to America. This is when the U-boats were not afraid of us.

BOB BALLARD: We hadn't got our act together.

NARRATOR: Not far from the Alcoa: an oil tanker, the S.S. Gulf Penn, 90,000 barrels of oil still trapped inside.

BOB BALLARD: These are, in some ways, ticking time bombs, in the sense that the hull will rupture, and you'll have oil come out.

Could you look at that wreckage? Could you look at the wreckage, before you go too far?

NARRATOR: But Ballard and Kohler's ultimate goal is a pair of shipwrecks, resting not far away: one, the hunter, the other, hunted.

This is the S.S. Robert E. Lee, the victim. In 1942, 407 souls walked these decks.

RICHIE KOHLER: On board the Robert E. Lee was not only passengers, but there were actually survivors from previous German U-boat sinkings that occurred out in the ocean.

BOB BALLARD: Square on the gun a little better.

NARRATOR: A three-inch deck gun had been added for protection against the U-boat threat.

RICHIE KOHLER: This gun never went into play. They never had a target.

BOB BALLARD: He's locked up, he's in a stored position.

NARRATOR: The attack came with almost no warning.

RICHIE KOHLER: You could almost imagine them standing along the side. Looking at what they thought was a porpoise and then it makes a turn and comes into them. It's actually a torpedo.

NARRATOR: Today, the fatal wound inflicted by the German torpedo is hidden beneath layers of silt on the ocean floor.

BOB BALLARD: It's amazing that most of the damage is not visible.

RICHIE KOHLER: Now, we're looking at a ghost ship. I mean it's obvious that it was abandoned. We can see where the four lifeboat davits were swung out.

Within five minutes these people were in the water fighting for their lives.

NARRATOR: Just over one mile away: the attacker, German U-boat U-166. Missing for 59 years, her rusting hull was spotted in May, 2001, during survey work for a new underwater pipeline.

But how did U-166 sink? Who was responsible? And why is she lying so close to her victim?

The official record offers little clue. For decades, the circumstances of this U-boat's sinking have been mired in controversy.

In 1942, a young destroyer captain, Commander Herbert Claudius, claimed credit for the kill, but the official report said Claudius botched the attack.

It was one man's word against the U.S. Navy, in a case obscured by the fog of war. Ballard and his team believe their technology, building on the earlier survey work, can finally put the question to rest.

BOB BALLARD: It isn't until fairly recently that this submarine's been found. So, I'm going to use my technology, and see if an injustice was done that needs to be corrected.

NARRATOR: It is a story that began three years before U-166 was sunk, before America had even entered the war, when Great Britain found itself facing off against Nazi Germany in one of the most pivotal conflicts of World War II: the Battle of the Atlantic.

Lasting from the first day of the war to the very end, the fighting would ultimately claim nearly 6,000 Allied and German ships and span 5,000 miles of ocean.

MARTY MORGAN: What was at stake was simply Allied survival in World War II. Now, at this stage of the war, England was standing alone against the rest of Europe, which had been conquered and brought under Nazi tyranny.

NARRATOR: If the British were defeated, the war would be all but lost.

ED OFFLEY (Author, The Burning Shore): There was no way that the Allies were going to be able to invade Normandy from Hoboken, New Jersey. It just wouldn't have worked. You needed a launchpad. The launchpad was England.

NARRATOR: But as an island nation, Britain was vulnerable. Its survival depended on supplies imported from abroad—raw materials, food, weapons—roughly 1,000,000 tons of cargo a year, crossing the Atlantic.

By 1941, the Nazis were close to cutting off that flow. The key to their success was the “Unterseeboot,” German for “underwater boat,” known to the rest of the world as the “U-boat.”

The Nazis built nearly 1,200 of these deadly machines. They were meant for one purpose only: to attack. At either end of the U-boat were tubes for launching torpedoes, 23-foot-long underwater missiles; at its center, the conning tower; below it, a maze of controls for steering, diving and surfacing.

Submerged, a U-boat's survival depended on its pressure hull. Invisible from outside, these structural ribs and steel plates were all that stood between the crew and thousands of tons of seawater.

Like today's hybrid cars, U-boats relied on a combination of internal combustion engines and battery-powered electric motors for propulsion. On the surface, air-breathing diesels could drive up to 18 knots, roughly 20 miles an hour. Under water, the electric motors took over, but the batteries were a critical vulnerability. They typically lasted less than 24 hours, and the diesel engines could only recharge them on the surface.

TIM MULLIGAN: A U-boat is ultimately a submersible rather than a true submarine. It's not intended to operate perpetually beneath the water. They have to be on the surface several hours every day, in order to recharge their batteries.

NARRATOR: And a U-boat on the surface was a target. Despite this weakness, the U-boats were stunningly effective.

MARTY MORGAN: The U-boat was the terrifying weapon of war, and it was especially terrifying when it took on unarmed ships that were carrying cargo.

NARRATOR: Commanding the German assault was Kriegsmarine Admiral Karl Dönitz.

TIM MULLIGAN: During World War I, he commanded a German U-boat. That's where he learns a lot of his lessons.

AXEL NIESTLE (Author, German U-Boat Losses During World War II: Details of Destruction): He could be harsh at times. But the U-boat men considered him a just leader. And that's why they followed him all through the war.

NARRATOR: With the U.S. still neutral, Dönitz focused his fleet on the British ships.

Wolf packs, groups of U-boats ranging from three to more than 20 subs, swarmed and overwhelmed the British convoys. Dönitz directed the wolf packs himself, via long range radio.

HOMER HICKAM (Author, Torpedo Junction): Admiral Dönitz was a very hands-on type of manager. He wanted to know where his U-boats were at all times. He required them to call in on a daily basis.

NARRATOR: The Allies could hear the transmissions, but they couldn't understand them. The Germans had a secret weapon: the code machine known as “Enigma.”

TIM MULLIGAN: The Enigma machine, itself, looks like a very elaborate typewriter that encodes and decrypts the messages, as they're sent and received.

NARRATOR: The secret of the Engima machine was its constantly changing code. With every keystroke, the code rotors that scrambled the message shifted slightly, generating a new code. No word would ever be encoded the same way twice. Every day, the sender and receiver set the rotors to a position listed in codebooks each operator carried.

The Allies had secretly copied one of the machines, but without knowing the settings, they had no hope of deciphering the messages.

By 1941, the Enigma-equipped U-boats were winning the Battle of the Atlantic. England was being starved into submission.

MARTY MORGAN: In fact, British Prime Minister Winston Churchill would later say that he only…there was only one thing that he feared during World War II, and it was the U-boat.

NARRATOR: Then, a breakthrough. In May of 1941, U-110 stopped reporting in. German command believed her sunk. In reality, she had been captured off the coast of Iceland. Her Enigma machine and the codebooks specifying the settings were shipped back to London. British mathematician Alan Turing and a secret team of codebreakers went to work.

TIM MULLIGAN: The British were able to break the German naval ciphers by the end of May, beginning of June, 1941. That was critical for saving British convoys for the rest of 1941.

NARRATOR: The Germans had no idea. Mathematics, not munitions, had bought the British crucial time, until December 7, 1941, when the Japanese bombed Pearl Harbor, and everything changed.

With America officially at war, U.S. ships could now be targeted. Admiral Dönitz seized the opportunity to tilt the battle back in Germany's favor.

MARTY MORGAN: He knows that right after Pearl Harbor, if he sends U-boats across to attack the U.S. Atlantic coast, he knows he'll get a big payoff, because the United States won't be ready.

NARRATOR: Dönitz believed his U-boats could cut England's lifeline of vital cargo, by striking at the source. Operation Drumbeat was born.

But with his U-boats stretched thin, Dönitz had only a handful of long-range boats, known as type-IXs, available to send to America.

TIM MULLIGAN: He assigns, I think it's six, type-IX U-boats. And then one of them falls out. So, it's only, initially, five type-IX U-boats to operate off the U.S. east coast.

NARRATOR: The trip to America took three weeks. British codebreakers warned the U.S., but in the wake of Pearl Harbor, the Navy had other priorities.

ED OFFLEY: Neither the U.S. Navy nor the Army Air Forces was prepared. Not only did they not have the airplanes and the ships available, but the ones they did have available did not have the sensors or weapons that could destroy a U-boat.

NARRATOR: Even basic protective measures were ignored.

HOMER HICKAM: You got to remember, all of Europe is blacked out now, and all the lights were on. There's just, there seems to be no alerts whatsoever.

NARRATOR: Officials worried a blackout could disrupt commerce, but no blackouts meant cargo ships were perfectly silhouetted against the bright lights.

HOMER HICKAM: They found, in effect, U-boat Disneyland. It was wonderful.

NARRATOR: Horst von Schroeter, was watch officer on U-123.

HORST VON SCHROETER (Watch Officer on U-123): We closed the shore within, say, two or three nautical miles. We smelled the forest ashore, and we saw the autos, the cars, running on the shore way.

NARRATOR: Erich Topp was commander of U-552 and the third-most successful U-boat commander of the war.

ERICH TOPP (Commander U-522): It was a shooting of hares. It was because the Americans, at that time, had not developed countermeasures against submarines. And so, we had very easy game there.

HORST VON SCHROETER: It took one week, as I remember, only. One week, all the time, and we sank, I think, 10 ships.

MARTY MORGAN: In fact, they return to their ports in the Bay of Biscay, coast of France, empty, having fired all of their torpedoes.

NARRATOR: By February 6th, barely three weeks after the first U-boats arrived in U.S. waters, they'd sunk 25 ships.

Spurred on by the success, Dönitz sent every U-boat he could spare across the Atlantic, including the newly built U-166, the wreck Ballard is closing in on.

On board the Nautilus, Ballard's team preps the R.O.V.s. The primary unit, named Hercules, is equipped with several high-definition cameras. Its sophisticated sonar will locate and map the wreck site. This technology will offer a view of the U-boat, with stunning clarity and detail.

Hercules can dive as deep as 2.5 miles, putting U-166 well within its reach. But, just like human divers, it doesn't go alone. Hercules is tethered to a second R.O.V., named Argus. Physically linked to the ship above, Argus acts as a stabilizer and light source for Hercules. It also sends video up to the Nautilus, so the crew can watch for potential hazards.

Hercules is kept on a short leash, to prevent its tether from getting tangled. Operating the R.O.V.s like this is tricky. The ship's computers must maintain its position directly above the wreck, so the R.O.V.s can safely navigate the site.

BOB BALLARD: So computers are driving the ship. Humans aren't driving the ship right now, it's being driven by computers. As we move the ship, we move Argus. And Hercules' job is stay out on point.

NARRATOR: It will take over an hour for the R.O.V.s to reach the wreck of U-166.

By March of 1942, Dönitz was sending nearly half of his combat-ready U-boats to attack America. The Germans had also regained a crucial advantage: a new Enigma machine.

TIM MULLIGAN: The German navy increasingly suspects that their cipher machine has been compromised, as indeed, it has been.

NARRATOR: Dönitz upgraded the Enigma machines on board his U-boats with an additional rotor. Overnight, the new machine, nicknamed “Shark” by the Allies, made their codebreaking useless.

AXEL NIESTLE: From then on, the Germans were well ahead in terms of information, because the Allies no longer could read what the Germans were planning.

NARRATOR: For Dönitz and the U-boats, the hunting was almost too good. They kept running out of torpedoes and fuel and had to travel 3,500 miles back home to resupply, until German engineers came up with an inventive shortcut: the type-XIV U-boat, dubbed the “milk cow.” The milk cows were not designed to fight.

AXEL NIESTLE: Instead of carrying offensive weapons they just carried extra fuel and provisions and even extra torpedoes for the U-boats.

NARRATOR: With 430 tons of fuel and supplies, the milk cows were floating gas stations. And the Germans had an ideal location to deploy them: the Atlantic Gap.

MARTY MORGAN: Aircraft based in North America, aircraft based in Iceland or Greenland or in the United Kingdom, their umbrella of coverage left a gap right in the middle. That mid-Atlantic gap was an area where U-boats knew that they could operate with impunity, because no Allied aircraft could reach that gap.

NARRATOR: The Germans seemed to hold every advantage. The U-boats were virtually unstoppable.

By April of 1942, three months into Operation Drumbeat, nearly 250 Allied ships had been lost in American waters. Not a single U-boat had been sunk.

AXEL NIESTLE: “Happy times,” they called it, in Germany, “Die Glückliche Zeit.” There were more targets available than they could cope with.

NARRATOR: And the U-boat missions were only becoming bolder. In June, 1942, the Nazis carried out one of their most daring attacks on America. Known as Operation Pastorius, the program used U-boats to land teams of Nazi spies on American soil.

MARTY MORGAN: The overall plan was that German saboteurs and spies would attack vital railroad bridges, that they would attack aluminum plants, aluminum plants that were making the skin of the aircraft that would ultimately drop bombs on German cities. And the U-boat contribution to this mission was vital. It couldn't have been done without them.

NARRATOR: Two teams of spies were landed, one on Long Island, New York, the other near Jacksonville, Florida. The spies dispersed into the civilian population, and began their preparations.

Meanwhile, Dönitz and the U-boats kept probing American defenses. They soon identified an enticing new weak spot: the shipping lanes in the Gulf of Mexico.

MARTY MORGAN: We had lapsed into the thinking that everything's fine in the Gulf of Mexico, because the enemy is not there. And Dönitz sends them into the Gulf of Mexico realizing that he'll get yet another big payoff with the Gulf of Mexico. And, oh, god, what a payoff he got!

In the month of May, 1942, he sank 41 ships. That's more than one ship a day going down in flames in the Gulf of Mexico.

NARRATOR: It was to this hunting ground that U-166 would be assigned for her first patrol in America.

Home movies recorded by U-166's captain, Hans-Gunther Kuhlmann, show the young crew training, just weeks before the mission. On June 17, 1942, they left port and set course for America. They would never be seen again.

BOB BALLARD: There's bottom.

RICHIE KOHLER: There you go.

NARRATOR: Aboard the Nautilus, Bob Ballard is trying to understand their final moments.

BOB BALLARD: What's it say? Target bearing?

RICHIE KOHLER: Target bearing is 230.

BOB BALLARD: Yeah, so we'll…it should show up on sonar. They're coming down close enough.

NARRATOR: After reaching American waters, in July of 1942, U-166 quickly sank three ships and was looking for more off the coast of Louisiana.

On the afternoon of July 30, another target appeared in her sights: the Robert E. Lee, making its way to New Orleans. U-166 launched a single torpedo; the passenger ship never fired a shot in return. Within minutes it was sunk.

But what U-166 didn't realize was that the Robert E. Lee was not alone. She had a naval escort ship, PC-566. Its captain was a young naval officer, Herbert Gordon Claudius.

GORDON CLAUDIUS (Son of Commander Herbert Claudius): He was a farm boy from Nebraska. And he I guess wanted to get out of Nebraska.

And then, of course, his first ship in the Navy was the PC-566.

NARRATOR: PC-566 had been commissioned only the month before. Claudius and his crew were about to see combat for the very first time.

MARTY MORGAN: As soon as a German torpedo struck Robert E. Lee, Claudius swings the PC-566 into action.

One of the men on deck of PC-566 observes a periscope in the water. Claudius then turns the vessel towards that periscope sighting. He's doing that in an attempt to approach from its blind side.

NARRATOR: A U-boat's periscope has a narrow field of view. With the U-166's lens pointed at the sinking Robert E. Lee, the German captain couldn't see the Navy ship coming.

BOB BALLARD: He's in the fray, right now. He's trying to kill this guy. He wants to sneak right up on top of that guy, so he can't get away.

MARTY MORGAN: He's bearing down on it as fast as he can, and when he's 120 yards away he sees the periscope retract.

BOB BALLARD: He's following the wake, and directly over the estimated position he's setting off a sequential series of five depth charges.

NARRATOR: The depth charge is an underwater bomb and the Allies' primary weapon against U-boats. The attacking ship estimates the location and depth of the U-boat, then sets the charges to detonate when they hit that depth. Water pressure triggers the explosion, sending a shock wave ripping through the ocean.

The explosion isn't powerful enough to blow up a U-boat. The idea is to simply crack its pressure hull, then let thousands of tons of seawater finish the job. But depth charges aren't necessarily a death sentence. The shock wave is only dangerous up close.

If the U-boat can dive out of range, she can escape.

U-boat crews had a series of carefully rehearsed procedures for trying to elude depth charges, as shown in this actual wartime footage.

The bow planes were set to maximum angle, driving the boat deeper. The electric motors were set to full power. Men who were not on duty ran forward; their weight helped point the boat down.

The emergency dive was the most critical test a U-boat crew could face. Seconds meant the difference between life and death.

Horst von Schroeter was watch officer on one of the first U-boats in Drumbeat, U-123.

HORST VON SCHROETER: From the order “Alarm,” it took 30 seconds to disappear from the surface, and another 30 seconds to be on a depth of 60 meters. And 30 seconds can be a long time in war.

NARRATOR: Werner Hirschmann was chief engineer on U-190.

WERNER HIRSCHMANN (Chief Engineer on U-190): I would call anyone who was not scared for his life under those circumstances a liar, because it is a scary experience to hear a depth charge dropping into the water, and then expect, in about five or ten seconds, an explosion to go off. There is nothing you can do. You can just sit there and wait, and this period of lack of activity is very unnerving.

NARRATOR: The crew of U-166 left no record of their final moments. They didn't send a radio report that day, or even a distress signal. All that is known comes from the report filed by Claudius. He dropped a second round of depth charges. An oil slick spread on the surface.

BOB BALLARD: So, now the periscope's no longer visible, the depth charges have gone off, there's no wake, you know? Did he kill it? And he sees an oil slick. You know, that's a very good indication that he hit it.

NARRATOR: In his report Claudius was clear.

HERBERT CLAUDIUS (Dramatization): (Reading from Report) …it is my opinion…that the sub was sunk or so mortally wounded that she would never return to her base.

BOB BALLARD: I mean this is the fog of war, but he is pretty confident that that oil slick is associated with that submarine.

RICHIE KOHLER: They attack the submarine. They come back and rescue the survivors, the 400 people that are in the water from the Robert E. Lee.

NARRATOR: Claudius radioed for help, knowing that his ship was too small to rescue everyone.

GORDON CLAUDIUS: It wasn't that big a ship, it was so top heavy that he actually had to load some of them back into lifeboats so his ship became stable. But then two other ships came out, and between the three boats they took them back to New Orleans.

NARRATOR: Claudius returned to port with the survivors; then, a shock.

RICHIE KOHLER: Instead of getting a hero's welcome, he was actually reprimanded. His entire attack is criticized. As a matter of fact, he's removed from command and then sent back to school. They didn't believe, not for one minute, that he had actually sunk the U-166.

NARRATOR: Senior commanders concluded that Claudius made a series of basic errors. They said he was in the wrong position while escorting the Robert E. Lee; he approached the U-boat the wrong way; and crucially, he deployed his depth charges too slowly and at the wrong depths.

BOB BALLARD: They're all saying “No way. No way did he sink this sub.” The attack was poorly conducted, and there is insufficient evidence to give higher assessment than an F. An F! Says F, right there. Flunked.

That's pretty humiliating.

NARRATOR: Gordon Claudius, Herbert's son, was only two years old at the time. He believes the review of his father was unfair.

GORDON CLAUDIUS: It was not favorable. He didn't talk much about his wartime activities. My sister was older than I was and more in a position to think about things and ask questions. And she said, well, she asked him one time and all he said was, well, he attacked a submarine and saw an oil slick and saw debris and that was it.

I think it not only got to my father, but I think it got to the whole crew.

NARRATOR: After the war, captured German records revealed that U-166 was the only U-boat lost in the gulf.

But the Navy concluded that U-166 had been sunk in an entirely different attack that took place two days later and 140 miles from where Commander Claudius gave chase.

MARTY MORGAN: A U-boat is spotted south of Houma, Louisiana, running on the surface, and a U.S. Coast Guard patrol plane attacks it with depth charges and then in the aftermath of the attack observes an oil slick on the surface of the water.

NARRATOR: The Coast Guard air crew was given credit for the kill, and so official history was written. Yet, despite decades of searching, a wrecked U-boat is never found at the location where the Coast Guard plane made its attack.

MARTY MORGAN: It's not for a lack of trying. People are going out on dive expeditions thinking that they have the exact spot where U-166 went down, but nobody finds it.

NARRATOR: Until 2001, when marine archaeologists from C & C Technologies made a surprising discovery during preparations for an undersea pipeline.

DANIEL WARREN (Marine Archaeologist): When we were looking at the extra data, and we saw the bow section…

ROBERT CHURCH (Marine Archaeologist): And at that point, we looked at each other, and we were like…

DANIEL WARREN: All the pieces came together. And it turns out it was the U-166.

ROBERT CHURCH: We knew, in that moment, that Lieutenant Commander Claudius and the crew of PC-566 had sank U-166.

NARRATOR: Yet 13 years later, the Navy record still denies Claudius credit.

BOB BALLARD: So, now we need to set the record straight, 'cause this guy died without recognition for what he did.

NARRATOR: Unless Bob Ballard and Richie Kohler can find a way to prove to the Navy that Claudius was responsible, the official record will stand as is.

A mile below, Ballard's R.O.V.s are closing in on the wrecked U-boat.

BOB BALLARD: Showtime. There it is. There she blows. Okay.

NARRATOR: She is in incredible condition, right where the previous survey said she would be.

RICHIE KOHLER: Looks like we could just blow off the dust, start the engines and go.

BOB BALLARD: Right.

NARRATOR: Two-hundred-fifty feet long, weighing 1,100 tons, in 1942, U-166 was a state-of-the-art killing machine. Now, she is a tomb.

RICHIE KOHLER: Oh, my gosh, that's a gun.

NARRATOR: So far, no damage is apparent,…

BOB BALLARD: Back up a little. Frame it a little. There we go.

NARRATOR: …though Richie Kohler sees evidence that the crew of U-166 knew they were in danger.

RICHIE KOHLER: There is a couple of telltale signs that this sub was in a, in a crash dive or trying to get down real quick. Number one, the aerial, the antenna that you see that's bent, that's a transmitting antenna.

BOB BALLARD: So, it wasn't….

RICHIE KOHLER: It's supposed to be retracted when they're diving.

BOB BALLARD: So he was too busy to do that?

RICHIE KOHLER: Everything stopped.

We've got the 20-millimeter gun that should have locked in position for underwater travel. It's swung out to port.

The periscope never came back down all the way. You can almost, you know, see these men are, are running to the forward end of the submarine, trying to get the bow heavier, trying to get it down, 'cause they knew trouble was coming.

BOB BALLARD: And they didn't make it.

RICHIE KOHLER: They didn't make it.

NARRATOR: It does appear the sub was running for its life. But, so far, they see no sign of the telltale fractures in the hull that two rounds of depth charges should have produced. The wreck seems surprisingly intact. And then, something strange.

BOB BALLARD: Now, that's not normal.

Could you stop right there, Will, and zoom in on that?

NARRATOR: Ballard zooms in, looking for the bow, the front of the sub. It appears to be buried in the sand, but it's not, it's completely gone.

There's no way a depth charge could have sheared off the bow of U-166 like this. So what happened?

The missing bow holds vital clues.

BOB BALLARD: We got to go find the other piece.

NARRATOR: The R.O.V.s move out across the sand. For many meters, there's nothing, then suddenly, it's the missing bow. And it's been reduced to scrap metal.

This is definitely not a depth charge.

RICHIE KOHLER: If that was a depth charge, we would not see this thin lattice work. This would've been totally blown away.

NARRATOR: Normally, a depth charge just cracks the pressure hull, but this is no fracture; it's an amputation.

RICHIE KOHLER: Most of the time, we see concave indents from depth charges. We don't see twisted and torn metal. At this level of destruction, it makes it difficult to ascertain what caused what.

NARRATOR: It's a conundrum. The location supports Claudius' claim that he sank this boat, but the damage doesn't match a normal depth charge attack, like the one Claudius made. To understand what happened, the team needs to put the two pieces of U-166 back together.

RICHIE KOHLER: We know that we've got this, up in the bow, separated. And then we don't know how much...

BOB BALLARD: Well, you know, we take the two pieces, and we see how much of it we see. Put them together and you see what you're missing.

NARRATOR: But the visibility is too murky to image the entire wreck in one shot.

BOB BALLARD: We can't see very far under water. I mean if you're lucky you can see 30, 40 feet.

NARRATOR: Fortunately, Ballard's R.O.V.s are equipped for just such conditions.

BOB BALLARD: What we'll do now is we've now outlined, and, so, we need to bring Clara up. Is Clara in the ready? So we can digitize this whole thing.

NARRATOR: Clara Smart is the team's high resolution mapping specialist.

As she watches, the R.O.V. does a sweep of the wreck, taking thousands of close up photographs with its ultra-high-resolution camera.

CLARA SMART (Mapping Specialist): The vehicle takes one image every three seconds, and what we're going to do is we're going to combine all these images to create…

BOB BALLARD: …one.

CLARA SMART: One very big beautiful…

BOB BALLARD: You can see it marching along.

CLARA SMART: Yep, and it's just matching one picture to the next. The whole idea, overall, is when we are on a site, we have a flashlight in a hay field, and you can't see anything, but once we make these maps, then all the lights came on, and we can see exactly what's down there.

NARRATOR: Clara will spend the next several months stitching the thousands of close-ups into a single giant wide shot, called a photo mosaic, that shows the entire wreck. Every rivet and crack will be visible, with unmatched clarity.

BOB BALLARD: We're able to get a picture you can't get any other way, a map that shows you what it would look like if you could take the water away. And that'll help tell us what happened to the submarine.

NARRATOR: Back at the University of Rhode Island, Clara gets to work. To start, computers assemble the images, but they can only do so much.

CLARA SMART: As you can see, we've got some issues.

NARRATOR: In problem areas, Clara will have to match individual frames by eye. It's a laborious process.

Finally, Ballard calls Richie Kohler and historian Marty Morgan to his lab. The mosaic of U-166 is complete. Thousands of photographs have been seamlessly meshed together.

But will the mosaic give the team what they need?

CLARA SMART: We took about 2,000 images with the R.O.V., and that's been boiled down to these two mosaics.

RICHIE KOHLER: This is really C.S.I. We're talking about 2,000 pictures, to give us one continuous image of what the U-166 looks like now.

CLARA SMART: Right. And it would be as if you were flying over with an airplane, you saw an aerial view.

NARRATOR: The key evidence lies somewhere in the break between the two pieces.

BOB BALLARD: That's where it all took place. The fact that this has been completely blown off…

CLARA SMART: And 100 meters away…

BOB BALLARD: And 100 meters away…

Yeah, you know, I think the question is was the depth charge enough power to literally tear off the front of a pressure hull?

RICHIE KOHLER: It's not really been seen before. In almost every instance…

BOB BALLARD: So you're led to believe that you, that you, there was another culprit in the mix.

NARRATOR: When the two pieces of U-166 are slid back together, they see that the break occurred right at the forward torpedo room.

RICHIE KOHLER: And interestingly enough, right here, where my finger is, is exactly where the torpedo tubes would have been loaded. You can see them clearly in the blueprints. We know they're there, but something destroyed the torpedo tubes.

BOB BALLARD: And there's how many torpedoes here?

RICHIE KOHLER: Four, four on the deck, four spare at reloads.

NARRATOR: Spare torpedoes were stored on the floor of the two torpedo rooms, the bow and the stern. If the forward torpedoes somehow exploded, while stored inside U-166, that could explain the incredible damage to her bow. If that is what happened, it points to an unlikely and catastrophic chain of events.

As U-166 frantically dove to escape, Commander Herbert Claudius dropped his depth charges.

BOB BALLARD: So, they were pretty shallow.

RICHIE KOHLER: Well, they were seen on the surface with their periscope up.

MARTY MORGAN: This is what has led me to believe the possibility of one of the five depth charges that were distributed by PC-566 landed on the deck there.

BOB BALLARD: And it carried it with them.

NARRATOR: Marty Morgan believes a depth charge landed directly on top of U-166. As the sub dove to escape, she carried the bomb down to its explosion depth, setting off a chain reaction that detonated her own torpedoes.

BOB BALLARD: That would make sense, because clearly it was so instant. He's just putting his periscope down. His dive angle isn't that great.

MARTY MORGAN: He probably wasn't even 30 feet deep.

BOB BALLARD: Right. So it very conceivably landed on him, clunk, and he carried the bomb.

MARTY MORGAN: Carries it down with him.

NARRATOR: Hustling forward to weigh down the bow, the crew may have run right into the exploding torpedo room.

RICHIE KOHLER: If you understand how the German submarines would dive, one of the things they would use the crew for is ballast. They would tell the crew to run. And that's exactly where it happened.

NARRATOR: The team is convinced. While a depth charge couldn't produce the damage seen on U-166, it could have detonated her torpedoes. Combined with the U-boat's location, it makes a persuasive argument. Instead of being reprimanded for his attack, Commander Herbert Claudius should have gotten a medal.

BOB BALLARD: Nice shot, perfect shot actually. Couldn't have done it better.

NARRATOR: But the team still faces a huge hurdle: convincing the U.S. Navy.

Ballard, a former Navy commander himself, puts their findings in writing and forwards them to the Chief of Naval Operations, the most senior officer in the Navy.

Seventy-three years after the battle, the Navy agrees to review the case.

Though it wasn't apparent it in 1942, even as U-166 sank to the bottom, Operation Drumbeat was already drawing to a close.

BOB BALLARD: The sinking of 166 is the first time we, actually, in the Gulf of Mexico drew blood.

RICHIE KOHLER: Didn't mean that we had taken the teeth away from the U-boats. No, they were going to continue to sink ships, but now, it was going to cost them. It cost them dearly.

NARRATOR: Allied science and engineering were finally beginning to turn the tide. Improved radar and high-frequency direction-finding meant the U-boats could be detected whenever they surfaced, even at night, while mass production of aircraft like the B-24 Liberator meant the Atlantic Gap was no longer a safe haven for the milk cows.

But the decisive stroke came with the capture of U-559, in October of 1942.

TIM MULLIGAN: What they get out of U-559 enables Allied codebreakers to regain that insight into the new Enigma machine, with its fourth rotor. And by the end of December, 1942, and certainly by the spring of 1943, the British and Americans can now read German U-boat signals in almost real time.

NARRATOR: The Enigma code was cracked once again. The U-boats had lost nearly all their advantages. Even the Nazi spies of Operation Pastorius, landed via U-boat to sabotage American industry, proved to be utter failures. All eight operatives were captured within days, and the Germans cancelled the program.

Never again would U-boats rule the seas. They had failed in their stated goal: cutting off the flow of supplies from America to England.

Yet, they had come dangerously close, and the damage caused by their attacks was immense. Hitler's U-boats sank 609 ships in American-protected waters. Over 3,000,000 tons of cargo never made it to Britain, and over 5,000 lives were lost.

On the German side, out of the 743 U-boats lost in World War II, only 10 were sunk in American waters. Of those, only one was sunk in the Gulf of Mexico: U-166.

But will the Navy give credit to Commander Claudius?

At the Navy History and Heritage Command, historians have analyzed Ballard's evidence, as well as reports from the marine archaeologists that first I.D.ed U-166. The two teams are nearly lockstep in their conclusions. It was Commander Claudius and his naval escort ship, PC-566.

ROBERT NEYLAND (Navy History & Heritage Command): The Underwater Archaeology Branch, here at Naval History Heritage and Command, looked at the information and confirmed that, absolutely, we believe that PC-566 did successfully attack and sink U-166. Whether it was skill, whether it was luck, or a combination of both, they were successful in the end.

NARRATOR: In 2014, 72 years after the battle, Admiral Jonathan Greenert, Chief of Naval Operations, and Secretary of the Navy, Ray Mabus, award Commander Herbert Claudius the Legion of Merit.

ADMIRAL JONATHAN GREENERT (Chief of Naval Operations/United States Navy): Good afternoon, everybody. We're here to recognize and actually to honor Lt. Commander Herbert G. Claudius. This is really, for me, a story of history, obviously, but also of explorers, of shipmates, of friends, of historians and, I think, relentlessness to set the record straight.

NARRATOR: Gordon Claudius, the only surviving child of Herbert Claudius, is here to accept the award on his father's behalf.

RAYMOND E. MABUS (United States Secretary of the Navy): Now, 70 years later, because of technology, we know that your father's after action report was absolutely accurate. And I think this is a good example of, “It's never too late to set the record straight. It's never too late to do the right thing.” So, it's an honor to be here today, to present your father, posthumously, with the Legion of Merit, for valiant actions during a very tough and very dangerous combat situation.

On behalf of your father, we present you with the V for Valor, which means it happened in combat.

GORDON CLAUDIUS: It sure did.

BOB BALLARD: This really brings closure on a story that began a month before I was born, 73 years ago. So this is a wrap, a nice wrap.

NARRATOR: So long after the conflict, World War II is fading history. Few remember the battles Herbert Claudius and other heroes once fought so close to our shores. But the sunken remains are still there, often nearer than we know, enduring reminders of just how close the Nazis came to setting history on a very different path.

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A Production of NOVA and National Geographic Studios for WGBH Boston in association with Lone Wolf Documentary Group.

© 2015 NGHT, LLC and WGBH Educational Foundation

All rights reserved

This program was produced by WGBH, which is solely responsible for its content.

IMAGE:

Image credit: (Wrecked Nazi U-boat, U-166)
© Ocean Exploration Trust, ROV

Participants

Robert Ballard
President, Ocean Exploration Trust
Robert Church
Marine Archaeologist
Gordon Claudius
Son of Commander Herbert Claudius
Homer Hickam
Author, Torpedo Junction
Werner Hirschmann
Chief Engineer on U-190
Martin K. A. Morgan
World War II Historian
Axel Niestle
Author, Details of Destruction
Ed Offley
Author, The Burning Shore
Erich Topp
Commander U-522
Horst von Schroeter
Watch Officer on U-123
Daniel Warren
Marine Archaeologist

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