In early 1943, the fate of the free world hung by a thread. That thread was the convoy route across the North Atlantic, and it was snapping. German Hubot operating in relentless wolf packs were sinking Allied ships faster than they could be built. In March alone, nearly a 100 ships were lost. Winston Churchill would later admit in his memoirs that the Yubot peril was the only thing that truly frightened him during the entire war.

Britain was just months away from starvation. The math was brutal and we were losing. But then almost overnight, the tide turned with a violence that no one, least of all the German captains, could have predicted. The hunters suddenly and catastrophically became the hunted. This is the story of the American secret weapon that broke the wolfpacks and left the aces of the deep in a state of shock. The hunter killer group.

To understand the shock, you first have to understand the situation in the Atlantic before 1943. It wasn’t a battle. It was a slaughter. German Admiral Carl Donuts, a brilliant and ruthless strategist, had perfected the rut tactic, the Wolfpack. His Ubot weren’t just lone hunters. They were a coordinated net of steel sharks.

They would stretch a patrol line across the known convoy routes, and when one boat spotted the merchant ships, it wouldn’t attack. It would wait. It would radio its position back to headquarters, and for the next day or two, every Ubot in range would converge on that single point.

Only then, usually at night, would they strike. A dozen submarines attacking from all directions at once. The convoy’s few escorts, usually destroyers and corvettes, were overwhelmed. They would race off to chase one submarine only for three more to slip inside the convoy and fire their torpedoes. For the merchant sailors, it was a living nightmare.

For the German yubot arm, it was the happy time. But this incredible strength concealed a fatal weakness. A weakness that once America figured out how to exploit it, would doom the entire yubot fleet. You see, a World War II submarine wasn’t a true submersible. Not like the nuclearpowered giants many of us remember from the Cold War.

Those boats can stay down for months. A yubot was really just a torpedo boat that could temporarily hide underwater. It was chained to the surface by two critical needs. First, it had to breathe. Its powerful diesel engines needed air and its massive batteries needed to be recharged by those engines, which meant spending hours every single day exposed on the surface. Second, it had to talk.

The entire Wolfpack system depended on constant radio communication. Every captain had to report his position, report convoy sightings, and get new orders. These two needs, breathing and talking, were the vulnerabilities. But Donuts had an ingenious solution for this too. He built a fleet of massive type 14 submarines known as Milchua or milk cows. These were not attack boats.

They were giant floating gas stations and resupply depots. A milk cow would meet a wolfpack at a secret rendevous point hundreds of miles from anywhere and top off their fuel, food, and torpedoes. This one invention allowed the Ubot to stay on the hunt for months at a time, turning the vast mid-Atlantic, an area beyond the reach of Allied patrol bombers, into a deadly black pit.

This is what the American fleet was up against. They realized that just defending the convoys was a losing game. You can’t win a war by playing defense. You have to go on the offense. You have to hunt the hunters. And that’s where the story begins. In the highest, most secret levels of the US Navy, a new organization called the 10th Fleet was formed. It wasn’t a fleet with ships.

It was a fleet of analysts and codereakers. Working with their British counterparts at Bletchley Park. They had achieved the impossible. They had cracked Enigma, the unbreakable German code machine. Suddenly, those constant radio transmissions from the Ubot weren’t just signals. They were confessions. The Allies knew where the wolf packs were.

They knew where the milk cows were meeting. But this created a new problem. How do you use that information? The Ubot were operating in the middle of the ocean, a thousand miles from the nearest Allied airfield. This mid-Atlantic gap was their sanctuary. The American solution was a marvel of ingenuity and raw industrial power, the Escort Carrier.

These ships weren’t the famous fleet carriers like the Hornet or the Enterprise, icons of the Pacific War. These were the Bogue class. They were small. They were slow and many were built on the hulls of merchant cargo ships. They were nicknamed jeep carriers or baby flattops, but they were a stroke of genius. Each one carried a deadly combination of around 12 F4F Wildcat fighters and nine TBF Avenger torpedo bombers.

They were in effect a mobile airfield that could go anywhere. On March 5th, 1943, the USS Bogue sailed from Norfolk, Virginia. She wasn’t part of a convoy. She was the core of Task Group 21.12, the first American hunter killer group. Her mission was simple. Go to the coordinates provided by Ultra Intelligence and erase the Ubot.

The German captains had no idea what was coming. They were used to facing destroyers, which they could hear coming on their hydrophones and dive to avoid. They had no defense against what came next. On May 22nd, 1943, an Avenger from the Bogue, piloted by Lieutenant William Chamberlain, picked up a radar contact.

Below him, U569 was on the surface, her diesels thrumming as her crew recharged the batteries. The lookout saw the plane, but it was too late. The Hubot began its crash dive. Chamberlain rolled his Avenger in. Four depth charges set for a shallow detonation bracketed the submarine as it passed under 50 ft.

The explosions ruptured the hull, forcing the boat back to the surface, mortally wounded. As another Avenger circled, the German crew scrambled out of the hatches, waving white flags. When the survivors were pulled from the water by a Canadian destroyer, they were in a state of shock. Their interrogators reported they kept asking the same question.

How did you find us? It was as if you could see through the ocean itself. This was their first brush with one of the hunter killer groups three secret weapons. The German hubot were equipped with radar detectors. They could hear Allied radar and would dive the moment they got a ping. But they were listening for the old radar.

The planes from the Bogue were using new highfrequency cinematic radar. It was completely invisible to the German equipment. An American plane could be right on top of them before the lookouts ever saw it. It was a devastating advantage, but it was only the first. The second secret weapon was called HFDF or Huff Duff.

This stood for highfrequency direction finding. This gear was installed on the destroyers escorting the carrier. The moment a yubot captain keyed his radio transmitter, even for a half-second burst, the huff operator would get an instant precise bearing to that signal. When two ships in the group got a bearing, they could draw two lines on a map.

Where the lines crossed, that’s where the hubot was. The Hunterkiller group could literally steer toward the hubot’s radio transmissions. The very tool that Dunit needed for his wolf packs was now a beacon leading the killers straight to his door. But the third weapon was the most terrifying of all. It was the one that killed them when they were in their only sanctuary, deep underwater.

In all the official documents, it was given a code name to disguise its purpose. The Mark 24 mine. It wasn’t a mine. It was a brand new top secret acoustic homing torpedo. Dropped from an Avenger, this torpedo, nicknamed Pho would parachute into the water and begin to circle. It had a small acoustic sensor in its nose listening.

The moment it heard the thrum, thrum thrum of a yubot’s propellers, it would turn and swim right at the sound. For a Ubot commander, this was the stuff of nightmares. You couldn’t see it. You couldn’t outrun it. And the very act of trying to escape, running your propellers was what guided it straight to your hull.

This combination of code breaking, new radar, huff duff, and acoustic torpedoes, all deployed from a mobile airfield, was the system that would annihilate the yubot fleet. Back in Germany, Admiral Donuts was seeing his losses mount at an alarming rate. The month of May 1943 was so catastrophic for his fleet, losing over 40 submarines that it became known as Black May. But Donuts was a hard man.

He believed his Yubot crews were the elite of the German military. His response to the new threat was not to withdraw. It was to fight back. He issued a new order. Yubot were to stay on the surface and use their powerful 20 mm and 37 mm anti-aircraft guns to shoot down the attacking planes.

This would prove to be a fatal miscalculation. On June 5th, 1943, aircraft from Bogue, located U27 on the surface. The German gun crews opened fire. The American pilots, veterans of the Pacific, were more than happy to oblige. The ensuing battle lasted for 18 minutes. The Wildcats strafed the deck, silencing the German guns while the Avengers lined up their attack runs.

The submarine was torn apart by depth charges and gunfire. It sank with all 50 of its crew. The pilot’s afteraction report was chilling in its brevity. Sunk sub zero survivors. The hunter killer groups were not just racking up kills. They were learning, adapting, and getting smarter. They realized that the true center of gravity for the wolfpacks wasn’t the attack boats themselves. It was the milk cows.

take out the resupply subs and the entire Wolfpack system would collapse. The attack boats would be forced to abandon their patrols and limp home on dwindling fuel. This new doctrine was perfected by another escort carrier, the USS Card, under the command of Captain Arnold Buster Esbull. The Card and her escorts became the most lethal submarine killing team in the Atlantic.

Their most spectacular victory came on August 7th, 1943. An avenger from the card flew over a patch of ocean and stumbled upon a yubot commander’s worst nightmare. It was the milk cow U17 caught red-handed in broad daylight, refueling another yubot, U66, with fuel hoses still connected between the two vessels. For the Ubot, there was no escape.

They couldn’t dive. The Avengers pilot, Lieutenant Charles Stapler, didn’t hesitate. He dropped his depth charges perfectly. The U117, loaded with hundreds of tons of diesel fuel and torpedoes, vaporized in a massive explosion. The pillar of fire and smoke was seen by other planes from 30 mi away.

The attack boat U66 was badly damaged, but managed to cut the hoses, crash dive, and miraculously escape. But the psychological damage was done. Its captain’s report to headquarters about the shocking attack was intercepted by the allies. This is the point where the shock truly set in. We can read it in the captured German war diaries.

Yubot captains were becoming terrified. One captain wrote, “The Americans appear everywhere at once. Their aircraft arrive without warning. Their weapons are impossibly accurate. We are no longer hunters, but the hunted. Even the most hardened aces, men who had been sinking ships since 1939, were breaking. Many veteran aces like Knights Cross recipient Hinrich Bleot, had already been removed from frontline command by late 1942.

Due to exhaustion and losses, they were reassigned to training roles as the Yubot campaign deteriorated. The Hunter Killer groups had presented the Yubot crews with an impossible choice. If you surface to charge your batteries, the new radar will see you day or night. If you transmit a radio report to your headquarters, Huff Duff will pinpoint your location.

If you stay deep underwater, you are blind, your batteries will die, and the Phtoes are listening for you. There was no right move. There was no escape. The only variable was how long you could survive. The sheer desperation led to some of the most bizarre and brutal close quarters battles of the entire war. On Halloween night 1943, the destroyer USS Borie, part of the USS Cards Group, got a radar contact.

It was U405 commanded by the experienced Ralph Heinrich Hopman. The Borie raced in, dropping depth charges that damaged the submarine and forced it to the surface. Hopman, unable to dive, made the desperate decision to fight it out on the surface. In the middle of a raging Atlantic storm, with waves crashing over both vessels, the Borie charged in to ram, but the helmsmen misjudged.

Instead of a clean hit, the Bor’s bow rode up onto the hubot’s for deck, and the two ships became locked together. For 10 agonizing minutes, it was a battle out of the age of sail. The crews, separated by only a few feet, fought each other with every weapon they had. Machine guns, pistols, shotguns. The Americans, unable to depress their main guns low enough, threw whatever was at hand.

Sailors hurled coffee mugs, empty shell casings, and even a sheath knife at the German gunners. Eventually, a wave tore the two ships apart. The Borie stood off and opened up with all its guns, firing over 4,000 rounds into the submarine. U45 sank, taking most of its crew, including its captain, with it. But the Borie itself had been mortally wounded by the ramming.

Her hull was slid open and she was taking on too much water. The next day, her own crew had to abandon her and scuttle the ship. It was a mutual kill, a battle of such primal ferocity that it showed the yubot war had entered a new desperate and final phase. If this history is as fascinating to you as it is to us, consider subscribing to the channel.

We post new videos every week, digging into the stories and strategies that define the 20th century. Hitting that button just lets us know you value this and it helps us keep making more. Germany, of course, tried to adapt. They were brilliant engineers. They introduced the snorkel, a breathing tube that allowed a yubot to run its diesel engines while remaining just under the surface.

But it was too little, too late. The hunter killer groups were now too numerous, too experienced, and too welle equipped. The quality of the yubot crews was collapsing. The veteran aces were almost all gone, replaced by young, inexperienced commanders, some barely out of their teens. Their training was rushed. Their crews were green.

They were being sent to sea in what were increasingly becoming iron coffins. This gap in quality was proven again on May 6th, 1944. The destroyer escort USS Buckley located U66, the same submarine that had barely escaped the USS Card’s attack on the milk cow U17 months earlier. Her luck had finally run out.

Once again, the Hubot was caught on the surface with dead batteries. Once again, it led to a desperate close quarters brawl. The Buckley rammed the Yubot and German sailors, fearing their boat was sinking, actually began climbing onto the American destroyer. The Buckley’s crew fought them off with small arms and famously hand-to-hand combat.

The destroyer backed away and pulverized the Yubot with gunfire. But the final symbolic end of the Yubot’s reign came just 2 days before D-Day on June 4th, 1944. Captain Daniel Gallery, commanding the USS Guadal Canal Hunter Killer Group, had a bold and frankly crazy idea. He didn’t want to just sink another Yubot.

He wanted to capture one. His group had been training for this in secret for months. They located U505 and hammered it with depth charges, forcing it to the surface. As the German crew bailed out, believing their boat was sinking, Captain Gallery gave the order. A boarding party from the USS Pillsbury leapt from their whaleboat onto the deck of the still moving, circling, and sinking submarine.

Led by Lieutenant Albert David, the men stormed down the Conning tower. They found the boat flooding with scuttling charges set to explode. In an incredible act of bravery, they found the charges, disarmed them, and managed to close the sea valves, saving the submarine just before it sank beneath them. They had done the impossible.

They had captured an enemy warship on the high seas. This was more than just a trophy. It was the intelligence jackpot of the war. The Americans captured the Yubot intact. They got its Enigma cipher machines, all of its current code books, operational manuals, and even its experimental acoustic torpedoes. Every remaining secret of the Yubot arm was now in Allied hands.

The war in the Atlantic was for all intents and purposes over. The U505 was towed to Bermuda and as many of you may know is now on permanent display at the Museum of Science and Industry in Chicago. It stands as a silent monument to the moment the hunters truly and finally captured their prey. When the D-Day landings began, the hubot was no longer a factor.

The invasion fleet sailed without fear of the wolfpacks. So when we say the German captains were shocked, it’s important to understand what that word really means. It wasn’t just the shock of a single new weapon. It was a deeper, more existential shock. It was the shock of a man who believes he is the apex predator only to discover he is being systematically herded by an intelligence he cannot see.

It was the shock of realizing that your every move is being watched. Your every message is being read and your every weakness is being exploited by a cold industrial and scientific system. The German yubot arm had brought more courage, skill, and determination to the fight than almost any other branch of the German military.

But the hunter killer groups prove that in modern war, courage is not enough. Of the 40,000 men who went to sea in the German yubot fleet, 30,000 of them, 75% never returned. It was the highest casualty rate of any service in any nation in World War II. The Hunter killer groups centered on those small unassuming jeep carriers hadn’t just won a battle.

They had changed the very nature of warfare. They wrote the blueprint for modern naval operations. a fully integrated system of intelligence, air power, and surface assets, all working as one to find and destroy the enemy. It was a system that dominated the seas in 1945. And it’s the very same system that the United States Navy with its massive nuclearpowered carrier strike groups uses to dominate the oceans of the world today.

The lesson learned in the cold, dark waters of the North Atlantic was a simple one. The lone wolf, no matter how brave, cannot survive against the coordinated, intelligent, and relentless pack. If you enjoyed this story, we’ve got another one you might like about the incredible engineering of the USS Nautilus, the world’s first nuclear submarine and a direct descendant of the lessons learned by these hunter killer groups.

You should see that video popping up on your screen right now. Thanks for being part of our community and we’ll see you on the next