In March 1943, German U-boats sank 120 Allied ships in a single month. Admiral Dönitz had 400 submarines and a stretch of open Atlantic where no aircraft could reach. Inside that gap, wolfpacks tore convoys apart for three and a half years.
Then something changed. Not a new battleship. Not a fleet carrier. Something built on a cargo hull in less than a year, so small its own crews had a nickname for the initials CVE — Combustible, Vulnerable, Expendable. Berlin didn't take them seriously.
What happened next was one of the fastest reversals in the history of naval warfare. And the German submariners who survived it left behind war diaries, patrol logs, and interrogation transcripts that trace the exact moment when the hunters realized they had become the hunted.
What they wrote — and what it reveals about a weapon they never identified, a code they never knew was broken, and a system they couldn't see — is in the video above.
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Then something changed. Not a new battleship. Not a fleet carrier. Something built on a cargo hull in less than a year, so small its own crews had a nickname for the initials CVE — Combustible, Vulnerable, Expendable. Berlin didn't take them seriously.
What happened next was one of the fastest reversals in the history of naval warfare. And the German submariners who survived it left behind war diaries, patrol logs, and interrogation transcripts that trace the exact moment when the hunters realized they had become the hunted.
What they wrote — and what it reveals about a weapon they never identified, a code they never knew was broken, and a system they couldn't see — is in the video above.
Subscribe for forgotten WW2 stories ▶️ https://www.youtube.com/@ww2dossierr
Like if you think this story deserves to be remembered.
Comment below — where are you watching from?
#worldwar2 #ww2 #militaryhistory #ww2stories #ww2dossier
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LearningTranscript
00:00August 7, 1943. Mid-Atlantic, 600 miles west of the Azores. Two German submarines sat motionless
00:08on the surface, side by side, connected by a rubber hose. U-117, a large mine layer,
00:15was pumping fuel into U-66, a Type 9 attack boat that had been wounded four days earlier by
00:21American aircraft. U-117 had also sent her doctor across by inflatable raft. Several of U-66's crew
00:29were injured, one badly. The sea was calm. The nearest land was a thousand miles away.
00:35The nearest Allied airfield was further still. There was no reason for an airplane to be here.
00:40Lieutenant Junior Grade Asbury Salinger saw them first. Flying a Grumman Avenger at 3,000 feet,
00:46he was 60 miles from his ship, a ship most German submariners didn't know existed. Salinger pushed
00:52his stick forward and dove toward the two dark shapes on the water. He had no fighter escort.
00:57He attacked alone. His depth charges straddled U-117. The explosion sent a column of white water
01:04between the two boats and severed the fuel hose. Both submarines began to separate,
01:09their crews scrambling across wet decks toward anti-aircraft guns. But Salinger had already radioed
01:15his carrier. Within 25 minutes, five more Avengers and four Wildcats arrived. U-66 crash-dived and escaped
01:23into the deep. U-117 was not so fortunate. A torpedo, a weapon the Germans didn't know existed,
01:30one that could hear the sound of their propellers underwater, found her hull. Sixty-two men went to
01:35the bottom. None survived. The aircraft that killed them had launched from the flight deck of USS Card,
01:41a ship built from a cargo freighter hull, displacing less than a tenth of what U-117's crew believed an
01:47aircraft carrier should weigh. The pilot who found them was 24 years old. The torpedo that killed them
01:53was powered by a motor designed for a washing machine. And the men who ordered U-117 to that exact
01:59position, at that exact time, had done so using radio signals that they believed were unbreakable.
02:05If this story matters to you, if you want these histories to reach the people who grew up with them,
02:10a like and a subscribe go further than you think. Here is what makes this story different from almost
02:16everything you have heard about the Battle of the Atlantic. For three and a half years,
02:20from September 1939 to the spring of 1943, the German U-boat was the most feared weapon in the
02:27ocean. It operated on a simple principle. Surface at night, find a convoy, fire torpedoes, disappear.
02:35The Atlantic was vast and dark, and largely empty of aircraft. A submarine that stayed below the
02:41horizon was functionally invisible. Wolf packs, groups of eight, 12, sometimes 20 U-boats, would
02:48converge on a single convoy and tear it apart over three or four nights. The merchant sailors who
02:54survived described the experience as being hunted by something they couldn't see, couldn't hear,
02:59and couldn't fight. By March 1943, Admiral Carl Donitz had more than 400 U-boats in commission. Over 120
03:07were at sea on any given day. That month, his boat sank 120 Allied ships, nearly 700,000 tons of
03:15cargo,
03:16fuel, food, and ammunition that would never reach Britain. There was a stretch of open ocean between
03:21Greenland and Iceland, 600 to 800 miles wide, where no Allied aircraft could reach. The submariners called it
03:29their safe zone. The British Admiralty called it the air gap. And inside that gap, convoys were on their own.
03:35Hold that fact, the air gap. Because what happened next is one of the fastest reversals in the history
03:41of naval warfare. And it started not with a battleship, not with a fleet carrier, not with a new submarine
03:47of
03:47their own, but with a ship that most American sailors considered a joke. She was 512 feet long. She could
03:54make
03:5419 knots on a good day. Her flight deck was so narrow that pilots called landing on it a controlled
04:00crash. She had been built in a
04:02commercial shipyard on a cargo hull in less than a year. She carried no armor. A single torpedo would
04:08have broken her in half. The U.S. Navy designated her an escort carrier, CVE. The men who sailed her
04:15had other names. Combustible. Vulnerable. Expendable. That's what the initials stood for, they said.
04:21The navy built them by the dozen, then by the score, then by the hundred. They were the smallest carriers
04:27afloat, and no one in Berlin took them seriously. No one in Berlin understood what they were for.
04:32Because these ships were not built to fight naval battles. They were not designed to project power
04:37across oceans. They were built for one purpose. To find German submarines and kill them. Not by defending
04:44convoys. Not by waiting for an attack. By hunting. By going into the open Atlantic with a handful of
04:51destroyer escorts and a squadron of aircraft and staying there. Days. Weeks. Until every U-boat within
04:58200 miles was on the bottom or running for home. The Germans had a word for what followed. They wrote
05:04it in their war diaries. In their patrol reports. In their letters home. In the trembling answers they gave
05:10to allied interrogators after being pulled from the sea. And when you read what they wrote. The
05:15captains. The engineers. The 19 year old torpedo mechanics. You can trace the exact moment when the
05:21hunters realized they had become the hunted. But to understand what those words mean. You have to
05:27understand what they lost first. And that begins with a number that Durnitz carried in his head like a
05:32prayer. 700,000 tons per month. That was the number. Durnitz calculated it in 1940. Refined it in
05:391941. And by 1942. He had made it the central equation of Germany's war at sea. If his U-boats
05:47could
05:47sink 700,000 tons of allied shipping every month. Consistently. Month after month. Britain would starve.
05:54Not metaphorically. The island imported 70 percent of its food. Nearly all of its oil. And every bullet
06:01fired by every soldier in every theater of the war. Cut the convoys. And the war was over. Durnitz was
06:07not
06:08guessing. He had built a system to deliver that number. He called it Rudel Taktik. Pack tactics.
06:14Though the allies would give it a more famous name. Wolfpack. The principle was elegant. A line of U-boats,
06:21spread across 50 or 100 miles of ocean, would wait for a convoy to cross their path. The first
06:27boat to spot smoke on the horizon would not attack. It would shadow the convoy and transmit a contact
06:33report to Durnitz's headquarters in Berlin. Durnitz would then vector every available boat toward the
06:38intercept point. They would converge at night, attack from multiple directions simultaneously,
06:44and overwhelm the escorts. It worked because of mathematics. A convoy escort group in early 1943
06:51typically had six or seven warships guarding 30 to 60 merchant vessels stretched across miles of ocean. A
07:02more threats than the escorts could answer. For every U-boat an escort chased, two more slipped through.
07:08And at night, on the surface, a U-boat was almost impossible to detect. She was low in the water,
07:14painted gray, running on diesel engines that left no wake. Radar in 1942 could barely find her.
07:21Sonar was useless against a surface target. Human eyes scanning a black horizon were the convoy's best
07:28defense, and they were not enough. The results were staggering. In 1942, U-boats sank over 6 million
07:35tons of Allied shipping. In the first 20 days of March 1943, remember this number, they sank 82 ships
07:43in the Atlantic alone, 476,000 tons in three weeks. The worst single battle was fought over convoys HX-229
07:52and SC-122 in mid-March. Sixty-three merchant ships sailing from New York to Liverpool ran into three
07:59wolf packs totaling 43 U-boats. Over four days, 22 ships went down. Oil tankers split in half and burned
08:07on the surface for hours. Freighters loaded with grain and ammunition broke apart so fast their crews
08:13had no time to reach lifeboats. 146 merchant sailors died in water so cold it killed a man in four
08:20minutes.
08:20In Berlin, the daily war diary of the U-boat command, the Befelshaber der Untersebute,
08:26or BDU, recorded the tonnage figures with something close to satisfaction. Dönitz briefed Hitler
08:32personally. The Führer, who understood almost nothing about naval warfare, understood that number.
08:38700,000 tons. His submarines were approaching it, and every one of those attacks happened inside the
08:44air gap. That stretch of open Atlantic where no Allied aircraft could reach was the Wolfpack's
08:50sanctuary. U-boats could surface there in daylight, charge their batteries, transmit without fear,
08:56and wait. A submarine that stayed submerged moved at four knots, walking speed. On the surface,
09:02she could make 17. Submersion was survival, but it was also blindness. A U-boat underwater could not
09:08find a convoy. She had to be on the surface to hunt, and the only thing that forced her down
09:13was an
09:13airplane. In the air gap, there were no airplanes. Dönitz knew this. He built his entire strategy
09:20around it. Every Wolfpack he assembled, every patrol line he drew across the chart, was positioned inside
09:26those 600 miles of open water where his boats could operate on the surface without fear of attack from
09:32above. The system depended on one assumption that he never questioned. Aircraft carriers belonged to the
09:37Pacific, to fleet battles, to the enormous blue water engagements between Japan and the United States.
09:44No one would waste a carrier hunting submarines in the middle of the Atlantic. And even if someone
09:49tried, a real carrier was too valuable, too slow to build, too important to risk against a torpedo
09:55that cost a fraction of its price. He was half right. No one would send a fleet carrier. But here
10:01is
10:01the fact that Dönitz did not have in his equation. The fact that would turn the number he worshipped
10:06into the number that killed his men. By the spring of 1943, American shipyards had figured out how to
10:12build an aircraft carrier in less time than it took Germany to train a single U-boat crew. Not a
10:17fleet
10:18carrier. Something smaller. Something expendable. Something that could be produced so fast and so
10:23cheaply that the United States could afford to lose them. And Germany could not afford to ignore them.
10:29The first of these ships was already at sea. She was called USS Bogue. She had sailed from
10:34Argentia, Newfoundland on the 5th of March 1943, with 12 Wildcats and 8 Avengers on her deck, screened
10:41by two old destroyers from the last war. Her crew included survivors from Lexington and Yorktown,
10:47men who had watched real carriers burn and sink beneath them. Now they were flying off a converted
10:52cargo ship in the North Atlantic in winter. Nobody aboard Bogue knew they were about to change the war.
10:58And nobody in Berlin knew they existed. But there was a problem. Because knowing how to build these ships
11:04ships was not the same as knowing how to use them. And the first man who figured that out nearly
11:09got
11:09himself killed in the process. Bogue's first three crossings were a disaster. Not the kind of disaster
11:14that sinks ships. The kind that makes admirals question whether the entire concept is worth the fuel.
11:20In March 1943, Bogue sailed with convoy HX-228 toward Liverpool. Her pilots flew patrol after patrol into gray
11:29skies and freezing rain. On the 10th of March, Ensign McCausland spotted a U-boat on the surface,
11:35the first submarine any of Bogue's pilots had ever seen outside of training. He dove to attack.
11:40His depth bombs failed to release. He came around for a second pass. They failed again. The U-boat
11:46slipped beneath the surface and disappeared. Bogue detached from the convoy the same day. After she left,
11:52the wolves found it. Ships went down. She tried again with convoy SC-123 later that month. No contact.
12:00No attacks. No result. She tried a third time. Nothing. Bogue returned to Argentia, then limped to Boston
12:07to repair a broken catapult. Her pilots had flown dozens of sorties in some of the worst weather on
12:13earth and had not scratched a single U-boat. The problem was not courage. The problem was doctrine.
12:18In the spring of 1943, escort carriers were assigned to convoys the same way destroyers were,
12:25as shields. They sailed with the merchant ships, flew patrols in a tight circle around the formation,
12:30and waited for the enemy to come to them. This meant the carrier was always where the convoy was,
12:36which was exactly where the U-boats expected to find aircraft. The submarines simply waited until the
12:41planes returned to refuel, then attacked in the gap. It took three crossings for the Navy to understand
12:46what one captain had been arguing since the day he took command. His name was Arnold Isbell. Most
12:52people called him Buster. He was 43 years old, from a small town in Iowa, and he had been flying
12:57Navy
12:58aircraft since 1924, back when the Navy's first carrier was an old collier with a wooden flight deck
13:04bolted on top. Isbell took command of USS Card on April 17th, 1943, and from his first day aboard,
13:12he told anyone who would listen that the escort carrier was being used wrong. The CVE was not a
13:18bodyguard, he said. It was a hunter. You didn't keep it tethered to a convoy like a dog on a
13:23leash.
13:23You turned it loose. You sent it into the open Atlantic with its own escorts, gave it intelligence
13:29on where the U-boats were gathering, and let it go find them. Remember that idea, because everything that
13:35follows, every German war diary entry, every terrified interrogation transcript, every desperate
13:41signal from a U-boat captain who could not understand how he was found in the middle of an empty
13:46ocean,
13:47traces back to that single shift in thinking. Defense to offense, shield to spear. But Bogue got there
13:55first, not because her captain invented the concept, but because Black May forced the Navy's hand. By the
14:01third week of May, 1943, the Atlantic was a slaughterhouse, and for the first time, the bodies
14:08were German. Forty-three U-boats were sunk that month alone. Twenty-five percent of every operational
14:14submarine doughnuts had. Eighteen were killed in convoy battles. Fourteen were caught by aircraft on
14:20patrol. The escorts had new radar that could find a submarine's periscope in heavy seas. Coastal Command
14:27Liberators were reaching deeper into the air gap. And the U-boats, following Donitz's own order to
14:33stay on the surface and fight back against attacking aircraft with anti-aircraft guns, were dying on the
14:39surface instead. On May 22, with Wolfpack Mosel still clawing at convoy ON-184, Bogue finally drew blood.
14:48Lieutenant Junior Grade William Chamberlain, flying an Avenger, caught U-569 on the surface and put two depth
14:55charges close enough to crack her hull. The captain ordered his crew topside and scuttled the boat.
15:01Twenty-four survivors were pulled from the water by a Canadian destroyer. It was one submarine,
15:06but it was proof. Two days later, on May 24, Karl Donitz sat at his headquarters in Berlin and made
15:13the
15:13hardest decision of his war. He ordered every Wolfpack out of the North Atlantic. The war diary entry is
15:19quiet, controlled. It attributes the catastrophe to the superiority of enemy detection equipment,
15:25and the surprise from the air which that equipment made possible. It does not mention that among the
15:3143 boats lost that month was U-954, a brand new Type 7C on her first patrol. Donitz does not
15:38mention
15:38that boat in his memoirs either. Her watch officer, the young man standing beside the captain when the
15:44depth charges found them, was named Peter Donitz. He was 21. He was the Admiral's younger son. Donitz
15:50pulled his boat south, toward the Azores, toward the coast of Africa, toward the routes where the
15:56air cover was thinner and the convoys less protected. He told himself and his commanders that this was
16:01temporary, that new weapons would restore the balance, that the Wolfpacks would return. What he did not
16:07know, what he could not have known, was that the retreat solved nothing. Because the Americans were not
16:13waiting for the Wolfpacks to come back. They were coming after them, and the man leading the hunt
16:18had just left Norfolk, Virginia, on the 27th of July, aboard a converted cargo ship with a flight deck,
16:24three old destroyers for escort, and a squadron of pilots who had never seen combat. Buster Isbell had
16:30his chance, and within 11 days, the Atlantic would belong to a different kind of hunter. Card sailed from
16:37Norfolk on July 27th, 1943, with 12 Avengers and nine Wildcats of Composite Squadron 1 on her deck.
16:45Her escorts were three flush-deck destroyers from the First World War, old four-stackers, thin-skinned,
16:51built in 1918. The youngest ship in the group was the carrier herself, and she had been a bare steel
16:57hull
16:57less than a year earlier. Captain Isbell did not sail toward a convoy. He sailed toward a set of coordinates
17:03that had been handed to him in a sealed envelope before departure. Those coordinates came from a
17:08place that Isbell was not told about, a place that did not officially exist, a brick building in
17:13Washington where Navy cryptanalysts were reading German radio traffic almost as fast as Donitz's
17:18own staff. The program was called ULTRA, and what ULTRA had decoded was something the Germans considered
17:24unbreakable, the schedule and position of their next submarine refueling rendezvous. Here is what you
17:30need to understand about the refueling system, because it was the spine of Donitz's entire
17:35Atlantic campaign. A standard Type 7 U-boat carried enough fuel for roughly 45 days at sea. A round
17:42trip from France to the mid-Atlantic convoy lanes burned most of that fuel just getting there and
17:47back, leaving barely two weeks on station to hunt. Donitz's solution was the Type 14 supply submarine,
17:53the Milchku, the milk cow. These were enormous boats, 1,600 tons, carrying enough diesel to refuel
18:01a dozen smaller submarines at sea. They also carried torpedoes, food, fresh water, spare parts, and a
18:08doctor. A single milk cow could keep an entire wolf pack operational for weeks beyond its natural endurance.
18:14By the summer of 1943, the milk cows were the most important submarines in the Atlantic. Without them,
18:20Donitz could not sustain operations anywhere south of the Azores or west of the mid-Atlantic ridge.
18:26Every attack boat that sank a freighter off Brazil, off West Africa, off the Caribbean,
18:32depended on a milk cow rendezvous to get home. And every one of those rendezvous required a radio signal.
18:38Donitz transmitted the coordinates by Enigma cipher, the U-boats acknowledged by Enigma cipher. Both signals
18:44were intercepted, decoded, and forwarded to the 10th Fleet in Washington. Admiral Ernest King's
18:50dedicated anti-submarine command, which plotted the position on a chart and sent an escort carrier to meet
18:56them. The trick was timing. If the hunter-killer group arrived too early, the U-boats would not yet be
19:01there. Too late, and they would have scattered. The group had to appear at the exact moment when
19:06two submarines were sitting motionless on the surface, connected by a hose, unable to dive. On August 7th,
19:1311 days into CARD's first offensive cruise, Lieutenant Junior Grade Asbury Salinger found
19:19exactly that. You already know what he saw. Two submarines, side by side, 600 miles from the
19:25nearest land. U-117, a large mine layer pressed into service as a provisional tanker, transferring fuel
19:33and her ship's doctor to the wounded U-66. Salinger dove alone and attacked. But now you know what he
19:39knew
19:39before he pushed his stick forward. Those boats were supposed to be there. The coordinates were
19:44not a lucky guess. They were a decoded German signal, transmitted four days earlier, received
19:50and plotted at 10th Fleet headquarters, and relayed to CARD by encrypted dispatch. U-117 never completed
19:57her mission. She went down with all 62 hands. And within three weeks, CARD's pilots sank three more
20:03submarines. U-6-64 on August 9th, U-5-25 on August 11th, and on August 27th, the big one,
20:11U-8-47. U-8-47
20:14was the last available provisional tanker in the Central Atlantic. She had refueled six U-boats that
20:20morning. Hours later, two Wildcats from CARD strafed her on the surface and forced her to dive. Lieutenant
20:26Junior Grade Ralph Long dropped a weapon into the water just ahead of the swirl where she had submerged.
20:32Three minutes later, the ocean erupted. U-8-47 went down with all 63 men. In four weeks, Isbel's group
20:39had
20:40killed four submarines and crippled the entire Mid-Atlantic refueling network. The milk cow that
20:45was supposed to supply a dozen attack boats was gone. The boats she was meant to refuel were now
20:51stranded, burning through their reserves, unable to reach their patrol areas, forced to crawl home on
20:57fumes. One dead tanker meant 12 patrols canceled. Two dead tankers meant a theater shut down. By the
21:04end of 1943, escort carrier groups had sunk five of the ten milk cows. Within a year, all ten were
21:11on
21:11the bottom. Not one survived the war. 289 of their crewmen were killed. They had the highest casualty rate
21:19of any submarine type in the Kriegsmarine. Dernitz knew he was losing his supply chain. His war diary
21:25entries from August and September reflect a man grasping for explanations. His boats were being
21:31found at coordinates that should have been secret. His rendezvous points were compromised before his
21:36submarines could reach them. He suspected treachery. He suspected spies. He investigated his own staff.
21:42What he never suspected, what he refused to believe until the evidence was placed in front of him at
21:47Nuremberg, was that his cipher had been broken. But the cipher was only half the weapon. Knowing where
21:53a U-boat would surface was useless without something that could kill it after it dove. And Card's pilots
21:59had been carrying that something in their bomb bays since July. A weapon so secret that the United States
22:04Navy refused to call it what it was. They called it a mine. It was not a mine.
22:09In December 1941, three days before Pearl Harbor, a group of physicists and engineers gathered at
22:16Harvard University's underwater sound laboratory to discuss something that had never been built,
22:21a torpedo that could hear. The concept was simple. An airplane catches a submarine on the surface.
22:27The submarine dives, which is what submarines have done since submarines existed. The airplane drops a
22:33weapon into the water, at the point where the submarine disappeared. But instead of sinking to a
22:37pre-set depth and exploding like a depth charge, which required the pilot to guess exactly where the
22:43submarine would be, and which missed far more often than it hit, this weapon would listen. Four
22:49hydrophones embedded in its nose would detect the sound of the submarine's propellers turning underwater.
22:54A vacuum tube guidance system would steer the torpedo toward that sound. The submarine could turn,
23:00could change depth, could run silent. But as long as her screws were spinning, the weapon would follow.
23:06The Navy gave the project a code name, FIDO. They classified it as a mine, Mark 24 mine, to keep
23:14the
23:14Germans from knowing what it actually was. The deception held for the entire war. German intelligence never
23:20identified it. German engineers never reverse engineered it. German submariners who survived its attacks
23:26never understood what had hit them. The speed of its creation was something that could only have
23:31happened in America in 1942. Bell Telephone Labs designed the guidance system. Harvard built the acoustic
23:38sensors. General Electric provided the propulsion motor, a 5.5 horsepower electric engine originally
23:44manufactured for household washing machines. Western Electric produced the batteries. David Taylor model basin
23:51handled the hydrodynamics. Four separate organizations, working in parallel with complete information
23:57sharing, built a weapon that had never existed before. The first prototype was test fired on December 7,
24:041942, the first anniversary of Pearl Harbor. It worked. Three months later, production models were rolling off
24:11the line. By May 1943, FIDO was at sea aboard escort carrier aircraft. 17 months from first concept meeting to
24:20first submarine killed. In the modern American defense establishment, a comparable weapon takes 10 to 15
24:26years. Now, imagine you are a German submarine commander in the autumn of 1943. You have been
24:33told that the mid-Atlantic is dangerous, that aircraft are everywhere, that milk cows are being sunk. But you
24:39are a veteran. You have survived 12 patrols. You know the drill. When an airplane appears, you sound the alarm,
24:46clear the bridge, and dive. 60 seconds, maybe 90, and you are under the surface. The airplane drops depth
24:54charges where it thinks you are. But you have already turned, changed course, gone deep. The charges explode
25:00behind you, above you, to the left. The hull groans, the lights flicker. But you are alive. You have done
25:07this before. Depth charges are a lottery, and the odds favor the submarine. Except now, something is
25:14different. You have dived on schedule. You have turned hard to port, and gone to 150 meters. The depth
25:21charges are detonating far behind you, nowhere close. You are safe. And then, three minutes after the
25:28last explosion, in silence, from a direction you did not expect, something hits your stern. Not a depth
25:35charge. Something that found you. Something that followed you through your turn, through your depth
25:40change, through your evasive pattern. Something that was listening. This is what FIDO did to the
25:46mathematics of submarine warfare. Before FIDO, the survival rate for a U-boat that crash dived before
25:52depth charges fell, was better than 90%. After FIDO, the odds collapsed. The Mark 24 mine sank 37 submarines,
26:01and damaged 18 more out of 204 fired. An effectiveness rate of 22%, more than double that of conventional
26:09depth charges. And because the Germans did not know it existed, they could not develop countermeasures.
26:14They could not deploy decoys. They could not change tactics to avoid a weapon they did not believe was
26:20real. Every escort carrier in the Atlantic carried FIDO from the summer of 1943 onward. The Avenger torpedo
26:27bombers of composite squadrons flying off Bogue, Card, Corps, Croatan, Block Island, and Guadalcanal
26:34dropped them into the Atlantic with the mechanical regularity of an assembly line. An Avenger would
26:39arrive over a diving submarine, wait for the swirl to settle, and release FIDO at 200 feet altitude and
26:46120 knots. The torpedo entered the water, began a slow spiral search, and waited for sound. If the
26:53submarine's propellers were turning, and they always were, because a submarine that stopped her screws would
26:58sink, FIDO found her. The weapon cost $1,800 per unit. A Type 7 U-boat cost 4.7 million
27:06Reichsmarks to
27:07build, and took 10 months to complete. Her crew of 44 to 52 men represented two years of training. FIDO
27:14killed
27:15them with a motor designed to wash clothes. Here is what makes this detail matter for the story we are
27:20following. By the end of 1943, the American hunter-killer system had three components that
27:26the Germans could not see and could not counter. Ultra told them where the submarines would surface.
27:31The escort carrier put aircraft over that position, and FIDO killed the submarine after it dove.
27:37Surface, and the aircraft finds you. Dive, and the torpedo follows you. Stay where you are, and the
27:44destroyer escorts close in with sonar and hedgehog mortars. There was no correct answer, and the men
27:50trapped inside those steel hulls knew it, because by the autumn of 1943, the things German submariners
27:57were writing in their logs had changed. In the early months of the war, when a U-boat returned
28:02to port in Lorient or Brest or Saint-Nazaire, the captain would stand on the bridge while the crew lined
28:07the deck and a brass band played on the quay. Penance flew from the periscope, one for each ship sunk.
28:14Officers received iron crosses from Durnitz himself, who came to the docks personally,
28:19shook every man's hand, and asked about the patrol. The crews were young, many of them under 25,
28:26and they carried themselves with the confidence of men who believed they were winning the war.
28:31They called themselves volunteers. They called their boats gray wolves. By the autumn of 1943,
28:37the bands had stopped playing. British intelligence was intercepting and translating prisoner-of-war
28:43interrogation reports as fast as captured crews could be processed. The change was visible in
28:48the transcripts. In 1941 and 1942, captured U-boat officers had been defiant. They boasted about their
28:57tonnage, quoted Durnitz's speeches, insisted that Germany's submarines would strangle Britain.
29:02By the summer of 1943, the tone was different. A report from June noted that recent prisoners were,
29:09as British officers recorded, dejected, though relieved to be out of the Battle of the Atlantic.
29:15The overwhelming confidence of earlier crews was disappearing. They had reason to be afraid.
29:21Between September and October 1943, 25 U-boats were sunk in the Atlantic. In return, they managed to
29:28torpedo nine merchant ships. Nine. For 25 submarines and roughly 1,200 men. The exchange rate had inverted so
29:37completely that every patrol was now a net loss for the Kriegsmarine. A U-boat that left port had a
29:431 in 4
29:44chance of never returning. By late 1943, that number would worsen to 1 in 3. By 1944, it approached 1
29:51in 2.
29:53Durnitz knew his crews were breaking. He could see it in the patrol reports, boats returning early with
29:58mechanical failures that may or may not have been real. He could see it in the signals, captains reporting that
30:04they had been forced under by aircraft and were unable to surface when their position suggested
30:09no aircraft were near. He could see it in the faces of the men he debriefed, men who had once
30:14begged for combat patrols, and now stood before him with the eyes of people who had already calculated
30:19their own odds. He tried to hold them. He distributed medals faster than ever before, a decoration for
30:25every man who completed a patrol, because a man who had done well should not go to sea unrewarded,
30:30as he would later explain at Nuremberg. He urged his captains to show a hunter's instinct and warrior
30:36spirit in the face of the Allied air threat. He told them new weapons were coming—acoustic torpedoes,
30:41radar detectors, faster boats. Hold on, he said. The technology will catch up. It did not catch up.
30:48In September 1943, Durnitz sent his wolf packs back into the North Atlantic, equipped with acoustic
30:54torpedoes, the T5 Zaunkonig, designed to home on the propeller noise of escort ships. The first
31:00attacks against convoys ONS-18 and ON-202 sank three escorts and six merchant ships. For 48 hours,
31:09it looked like the wolf pack had returned. Then the Allies deployed Foxer, a towed noisemaker that drew
31:14the acoustic torpedoes harmlessly into the wake behind the ship. Within weeks, the Zaunkonig was
31:19neutralized. The wolf packs that Durnitz had reassembled with such desperate hope were destroyed.
31:25More boats went down. More crews did not return. And the Navy was forced to cross a line it had
31:30never
31:30crossed before. Since the founding of the U-boat arm, submarine service had been voluntary. Every
31:36man aboard a U-boat had asked to be there. By the end of 1943, that was no longer true.
31:42Rear Admiral
31:42Francis Lowe, chief of the American 10th Fleet, reported publicly in September that the German Navy was
31:48nearing demoralization, similar to 1917, and had already been forced to draft U-boat crews.
31:55The men climbing through the hatches of boats leaving Brest and Bergen were no longer volunteers.
32:00They were conscripts, men who had been told, not asked, to enter what their own sailors had begun
32:06calling the Iron Coffin. The numbers tell the rest. Over the course of the war, roughly 40,000 men
32:12served in German submarines. 30,000 of them, 75 percent, were killed. It was the highest casualty
32:19rate of any branch of the German armed forces. Higher than the Waffen SS. Higher than the Luftwaffe's
32:25night fighter pilots. Higher than the Wehrmacht divisions that bled out on the Eastern Front.
32:30Three out of every four men who boarded a U-boat did not survive the war. And the instrument that
32:35killed
32:36more of them than any other single weapon system was the American escort carrier Hunter Killer Group.
32:42By the Navy's own accounting, CVE groups were responsible for approximately 60 percent of all
32:47U-boats sunk by American forces in the Atlantic between April and September 1944. Not shore-based
32:55aircraft. Not fleet destroyers. Not minefields. Escort carriers. The ships the Germans had dismissed as
33:02insignificant, built on cargo hulls, flown by pilots who had never seen a fleet engagement.
33:08Dönitz's war diary from October 1943 contains an entry that his staff could barely bring themselves
33:14to write. The enemy's attempts to restrict our operations, it reads, have succeeded. Eight words.
33:21No excuses. No promises of new weapons. But there was one thing left that Dönitz believed the Americans
33:27could never do. One humiliation that the entire German submarine command considered so unlikely
33:33that they never trained their crews for the possibility. They were wrong. And the man who
33:38proved them wrong was already at sea aboard another converted cargo ship, rehearsing something that
33:43had not been done since 1815. June 4, 1944. 150 miles west of Cape Blanco, French West Africa. Two days
33:54before the invasion of Normandy and 5,000 miles from Omaha Beach, a different kind of American
34:00operation was underway. USS Guadalcanal had been at sea for three weeks without a contact. Her task
34:06group, five destroyer escorts and a single escort carrier, had been hunting U-boats off the African coast,
34:13and the ocean had given them nothing. Captain Daniel Gallery, commanding from Guadalcanal's bridge,
34:18was low on fuel and overdue in Casablanca. He had just ordered his group to reverse course,
34:24when the destroyer escort Chatelaine's sonar operator reported a contact. Bearing was 210 degrees.
34:31Range was close. Gallery did not hesitate. He launched two Wildcats and an Avenger,
34:37and ordered Chatelaine to attack. The submarine was U-505, a Type 9 sea boat returning home after an
34:4480-day patrol in the Gulf of Guinea. She had been at sea so long that her crew had forgotten
34:49what land
34:49smelled like. Her captain, Oberlieutenant Harold Lang, was making his first patrol in command. He was
34:5636 years old, and he had inherited a cursed boat. U-505 had already lost two previous commanders,
35:03one relieved for psychological breakdown, another shot by his own crew in a struggle on the bridge.
35:09Chatelaine dropped her first pattern of depth charges. The explosions shook U-505, but did not
35:15kill her. The second pattern was closer. Relief valves blew across the boat. Pipes cracked in the
35:21engine room. The hull rolled so far onto her beam that men were thrown from their stations. Shouts of
35:28panic came from the aft compartments. Water was coming in. The rudder was jammed. The auxiliary controls
35:34were gone. Lang made a decision in seconds. He ordered his crew to blow tanks and abandon ship.
35:40The submarine erupted to the surface barely 700 yards from Chatelaine's bow, her conning tower
35:46streaming seawater, her crew already climbing through the hatches and jumping into the ocean. Wildcats
35:52overhead strafed the deck to keep anyone from manning the guns. One German sailor was killed, the only
35:58fatality. The rest went into the water. What happened next was something the German submarine command had
36:04considered so improbable that they had never issued procedures for it. Gallery had been planning for
36:10this moment since January. After his task group had sunk three U-boats on previous cruises, U-544, U-515,
36:19and U-68, he had returned to Norfolk and ordered every ship in his group to prepare a plan for
36:24capturing a
36:25U-boat at sea. Boarding parties were assembled. Procedures were rehearsed. Grappling hooks and tow
36:31lines were staged on deck. Gallery had authorization from the Navy to attempt what had not been done by
36:37American sailors in 129 years. USS Pillsbury lowered a whale boat. The boarding party was led by Lieutenant
36:45Junior Grade Albert David, a 22-year-old from Maryville, Texas. David had no way of knowing whether
36:51the submarine was booby-trapped. He had no way of knowing whether armed Germans were still inside.
36:57He had no way of knowing whether the boat was sinking beneath him as he climbed down the ladder
37:01into the conning tower hatch. He went anyway. Inside, David and his men found the boat abandoned but
37:08still running, her electric motors turning, her rudder jammed, water pouring in from a single open
37:14strainer valve. One German sailor, a mechanic named Hans Goebeler, had been the only crew member with the
37:21presence of mind to try to scuttle the boat. He had opened one valve. It was not enough. David's
37:27team closed it, stopped the flooding, and shut down the engines. A larger salvage party arrived from
37:32Guadalcanal, led by Commander Earl Trocino, the carrier's chief engineer. Within hours, they had
37:38stabilized the boat and attached a tow line. Guadalcanal towed U-505 2,500 miles to Bermuda. The captured
37:46submarine yielded code books, Enigma settings, acoustic torpedo manuals, grid charts, and operational
37:53documents that Allied intelligence would exploit for the rest of the war. The crew, 58 men, were
37:59taken aboard Guadalcanal and held in complete secrecy. For the remainder of the war, the German
38:05Navy believed U-505 had been sunk with all hands. They never knew she had been captured. They never
38:11changed their codes. Albert David received the Medal of Honor, the only one awarded in the Atlantic fleet
38:16during the entire war. Gallery received the Distinguished Service Medal. The task group
38:21received a Presidential Unit Citation. The citation's language is restrained. It does not mention that
38:27Gallery's sailors fought the Germans on the submarine's deck. It does not mention that David
38:31went down that hatch knowing he might not come back up. U-505 sits today in the Museum of Science
38:37and Industry in Chicago. You can walk through her hull. You can stand in the control room where David stood.
38:43You can put your hand on the valve that Goebbler opened.
38:4649 feet of steel, 700 miles from the nearest ocean, preserved in a climate-controlled building
38:52visited by school children, who do not know that the boat they are touching was the last enemy warship
38:57captured at sea by the United States Navy. The capture confirmed what the interrogation reports,
39:02the war diaries, and the patrol logs had been saying for months. By the summer of 1944, the German
39:09submarine force was no longer fighting to win. It was fighting to survive. And Karl Donitz, who had built
39:15that force from three boats in 1935 to 400 in 1943, already knew the words he would use to explain
39:22what
39:23had destroyed it. On the 6th of May, 1944, nine months after she escaped the attack that killed
39:29U-117, U-66 surfaced in the darkness, 400 miles west of the Cape Verde Islands. She had been hunted
39:37for
39:38five days by aircraft from a new escort carrier, USS Block Island, and she was trying to run on the
39:44surface under cover of night. The destroyer escort USS Buckley found her. What followed was the kind of
39:50battle that belongs to a different century. Buckley closed at flank speed and rammed U-66
39:56amid ships. The two ships locked together, steel grinding against steel, and for several minutes
40:02German submariners climbed from their conning tower onto the deck of the American ship. Buckley's crew
40:08fought them off with rifles, pistols, hand grenades, and, according to the after-action report, a thrown
40:15coffee mug. U-66 broke free, circled once, and sank. Her captain and most of her crew went down with
40:23her.
40:23The boat that had escaped Salinger's attack on August 7th had been found again, by another escort
40:29carrier, in another stretch of ocean that was supposed to be empty. There was nowhere left to
40:33hide. That same spring, Admiral Dunitz sent fifteen U-boats toward the Normandy beaches on the 6th of
40:40June, 1944. Eight had no snorkel, the breathing device that allowed a submarine to run her diesels while
40:47submerged. The war diary entry for that day is one sentence. For those boats without snorkels,
40:53it reads, This means the last operation. Ten of the fifteen were sunk within three weeks.
40:59On the 5th of July, allied hunter-killer groups were authorized to roam the western approaches and
41:05Bay of Biscay freely. The U-boats' own waters became a killing ground. Dunitz never stopped sending men to sea.
41:12New boats left Norwegian ports in 1945, crewed by conscripts, carrying experimental equipment that had not been tested,
41:19sailing toward an Atlantic that was no longer an ocean, but a cemetery. When Germany surrendered
41:25on May 7th, 1945, the surviving U-boat captains received a single, coded signal, Reaganbogen,
41:33Rainbow, the order to scuttle. Over two hundred submarines sank themselves in harbors and fjords,
41:39rather than surrender. The men who had once hunted in wolf packs chose to drown their own boats in
41:44silence. By then, the man who had turned escort carriers into submarine killers was already dead.
41:50Captain Arnold Isbell never received the fleet carrier command he had earned. On March 19, 1945,
41:58he was aboard USS Franklin as a passenger, en route to take command when a Japanese bomb struck the ship
42:04off Okinawa. Isbell was among the more than 800 killed. He was 45 years old. The destroyer the Navy
42:11named after him, USS Arnold J. Isbell, was commissioned as a hunter-killer ship. Daniel Gallery retired as a
42:18rear admiral. He wrote books about the capture of U-505 and spent years campaigning to save the
42:23submarine from the scrapyard. He succeeded. The boat he captured sits in Chicago to this day.
42:29Carl Donitz stood trial at Nuremberg. When asked to explain the collapse of his submarine force,
42:35he spoke carefully, as a man does when he is describing the death of something he built with his
42:40own hands. The airplane, he told the court. The surprise by airplane and the equipment of the
42:45planes with radar, which in my opinion is, next to the atomic bomb, the decisive war-winning invention
42:51of the Anglo-Americans, brought about the collapse of U-boat warfare. He served 10 years in Spandau prison.
42:58He was released in 1956. He never spoke publicly about his son Peter. Here is what the German
43:04submariners wrote. They wrote that the sky had become the enemy. They wrote that they could no
43:09longer surface to charge batteries without being found within the hour. They wrote that aircraft
43:14appeared from directions where no airfield existed, over water where no carrier should be. They wrote
43:20that something followed them underwater, something they could not hear, could not see, could not evade.
43:26They wrote that the men who left on patrol did not return, and that the men who replaced them were
43:31younger and more frightened and less trained. They wrote that the iron coffin was no longer a joke.
43:37What they were describing, in the language of men who did not yet know they had lost,
43:41was the sound of an industrial democracy that had decided to solve a military problem
43:46the way it solved every other problem, by building something ordinary, building it fast,
43:52building it in numbers that no one believed possible, and handing it to 24-year-old pilots who had
43:58learned to land on a cargo ship in a North Atlantic storm. The escort carriers did not win the battle
44:03of the Atlantic alone, but they broke its back. And the men who sailed them, on flight decks so narrow
44:09that one gust could send a plane into the sea, did it in ships that the navy itself called combustible,
44:16vulnerable, and expendable. The Germans called them something else. They called them the reason the ocean was
44:22no longer theirs.
44:23Thank you for watching this all the way through. If this story meant something to you, I'd be grateful
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44:49And if someone in your family served in the Second World War, in the Atlantic, in Europe,
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