German Commander’s Last 90 Seconds – The Weapon That Destroyed 47 U-Boats

May 23rd, 1943, North Atlantic, 540 km southwest of Ireland. Capitan Lloyd Nand Bernhard Mueller stood in the conning tower of U672, scanning the gray horizon through his Zeiss binoculars. The sea was calm, too calm. After five war patrols spanning 18 months, Miller had learned to trust that feeling, the instinct that separated the living from the dead.
Below deck, his crew of 48 men moved through the yubot with the efficiency of men who understood that every minute in these waters was borrowed time. U672 was a type 7 submarine, the workhorse of the German Navy. She could dive to 200 m. She could stay submerged for 36 hours. She had survived this long because Mueller made decisions that other commanders wouldn’t.
Aggressive when aggression mattered, careful when caution meant survival. Then he heard it, not through the hydrophone, through the air. A sound that shouldn’t exist. Multiple distinct splashes as if someone was dropping stones into the water in a perfect pattern around them. He grabbed the voice pipe. Hydrophone operator.
Immediate report on all contacts. What are we hearing? The response came back. Her Capitan, the instruments show nothing. No ship signatures, no aircraft engines, just the splashes. Müller’s jaw tightened. He had been trained in every aspect of submarine warfare. He understood how to read the ocean. He understood how to hunt.
He did not understand this. Hard to starboard. Dive to 60 m. Silent running. Now below deck, the claxons blared. The crew scrambled. The diesel engines cut off. Electric motors engaged. U672’s bow tilted downward. Bernhard Mueller was not a man prone to panic. At 31 years old, he had already sunk seven Allied merchant ships totaling 38,000 tons.
He held the Iron Cross, first class. He had looked at death underwater enough times to understand its mechanics. Every crisis had logic. Every situation had a response. Depth charges were predictable. You heard them fall, counted the seconds, waited. Aircraft attacks were terrifying, but comprehensible.
They could only see you on the surface. Mueller’s crew trusted him because he brought them home alive. 42 of the 48 men had served with him for at least 2 years, they knew his patterns. They knew that when Müller made a decision to attack, to dive, to run. It was based on operational experience earned through survival. U672 had been commissioned 6 months earlier.
She was fast. Every patrol taught Mueller how to keep a submarine alive in 1943 when the odds against Germany’s underwater war were shifting noticeably. The Yubot campaign that had been so successful in 1942 was becoming increasingly dangerous. In late 1942, Germany had sunk 119 Allied merchant ships in November alone, over 700,000 tons.
But 1943 brought something different. Allied detection methods had improved. Convoys were being routed away. Experienced commanders were being forced to abort attacks. Mueller had heard rumors in the mess at Laurant. Secret weapons, improved radar, something completely new. But every day alive was evidence he was doing something right until May 23rd, 1943.
Müller descended to the control room. First watch officer Klaus Shellinger waited at the periscope. Her Capitan destroyer contact bearing red 135 single screw 18 knots approaching from the north. It’s a modern escort moving with military precision. Distance 4,000 m beyond visual range. Miller nodded. A destroyer that was manageable.
The real prize was always the convoy it was escorting. This was why he had come to the Atlantic to find moments like this. To strike at the supply lines that sustained the British war effort. Full stop, Miller ordered. All crew to minimum noise. Silent running. We wait. The hubot went silent. The hydrophone operator monitored the destroyer’s approach. Twin screws.
That’s a British flower class. 3,000 m still closing. Mueller felt something shift. A flower class meant escort duty. It meant a convoy nearby. It meant opportunity. But it also meant perhaps 3 hours before the destroyer’s patrol brought it directly overhead. The destroyer’s sonar was active, but German hydrophones could detect it.
The destroyer would pass directly overhead in approximately 90 minutes. Mueller did not know what he could not know. The destroyer was not alone. Behind it, HMS Oral was maneuvering for position, and above, vetored by radio intercepts, a Lockheed Hudson aircraft was altering its patrol course to overfly his position at dusk. The tension aboard a submerged yubot waiting for an escort to pass overhead cannot be conveyed adequately.
48 men, no ability to maneuver, no ability to run, just listen to the destroyer’s propeller become louder. Miller sat in his chair. He did not move. His men knew not to speak. The hydrophone operator had his headset pressed tightly. Time moved differently underwater, waiting. Destroyer bearing red one 0. Distance 1,000 m. Miller nodded.
The destroyer would pass over them in 4 minutes. Distance 500 m. The destroyer’s screws became unmistakable. That characteristic churn of a steam turbine. You could feel the vibration through the pressure hull. Distance 200 m. Directly overhead. Miller’s hands were relaxed on the table. This was the moment. This was when destroyers attacked, but no depth charges came.
The destroyer passed overhead and faded. The hydrophone operator heard its machinery clearly. Destroyer at zero distance. Moving away. No attack pattern. Müller released a breath. The destroyer had not detected them. His position remained secret. In another hour, when darkness came, he could risk a surface attack. That was all he needed.
Maintain silent running, he ordered. Continuous monitoring. Report any change. What he did not know was that HMS Oral was maneuvering for position ahead. What he did not know was that he had approximately 6 hours to live. Full darkness came at 2030 hours. Miller ordered the yubot to surface. The ballast tanks blew. The deck vents opened.
U672 rose through the dark water toward the surface. Miller felt the boat transition from submarine to surface vessel. That familiar moment when the yubot became faster, more nimble, more deadly. On the surface at night, a yubot was a hunter with every advantage. The conning tower broke through the surface. Miller was already on deck, his night vision adapted to the darkness.
He could see the convoy, the shapes of seven merchant vessels, perhaps 30 km away, slightly illuminated by the light of stars. No moon, perfect conditions. The destroyer was still visible as a faint shadow to the north. Battle stations, prepare all torpedo tubes for attack. The order rippled through U672. Mueller had trained this crew perfectly.
They moved with the precision of men who understood that every second mattered. The torpedo crew raced to the tube room. Shelinger calculated the firing solution. Speed, distance, the geometry of death. Miller raised his binoculars. He could see the lead merchant vessel, a British freighter, perhaps 3,000 tons.
Easy target, then the second vessel, a larger cargo ship, then the third. This convoy represented perhaps 22,000 tons of Allied supplies. Miller did not think about the men crewing these vessels. He thought about the supplies, the ammunition, the fuel, the food needed to continue the war against Germany.
Every ton he sank was a ton the allies could not send to the United Kingdom. He called to Shelinger. Estimate 12,000 m to the nearest merchant vessel. Destroyer bearing red 340 8,000 m distant, moving northeast. Solution ready in 30 seconds. Mueller watched the merchant ships. At this distance, his torpedoes would take approximately two minutes to reach their targets.
The destroyer would take roughly 5 minutes to react to an attack. If the first torpedo struck home, Müller would have time to fire again. He could sink two, possibly three merchant vessels before the destroyer reached firing range. “Solution ready,” Shelinger called. The firing solution was perfect. Distance, speed, angle, everything aligned.
Miller raised his hand. First salvo, all bow tubes. fire. The torpedoes left the tubes. Two type 7CG7E standard electrics running at 35 knots toward the convoy. Mueller turned to give orders for the second salvo. Then the sea around him exploded. Not ahead where the merchant ships were. All around him, a pattern of splashes, enormous, violent splashes erupting from the water in a perfect geometric arrangement directly in front, behind, to port, to starboard.
Miller had never seen anything like it. Crash dive, he screamed. Hard to starboard. All hands brace for impact. But there was nowhere to dive. The water was 300 m deep. The splashes were not depth charges. They did not arc down and explode below. They were something else, something that hit the water at extreme velocity.
The first projectile struck the conning tower. It was not large, perhaps 1 kg, but it was traveling at 400 m/s. It punched through the steel plating of the conning tower like a bullet through paper. The projectile detonated on contact with the pressure hull. Miller felt the impact more than heard it.
A wrenching, tearing sensation as the structure of his boat was violated. He felt himself falling. The world was spinning. He tasted blood. His ears were ringing from the concussion. Around him, U672 was coming apart. The conning tower filling with seaater. The superructure torn open in three separate places. Below deck, the impact had torn open the forward torpedo room. Water was pouring in.
Men were screaming. The boat was tilting. The pressure that had kept the Atlantic at bay was now being violated in dozens of locations simultaneously. Mueller pulled himself toward the voice pipe. Flood all compartments. Get the men up. We are sinking. This was no longer submarine warfare. This was slaughter.
The second pattern of projectiles arrived. Then the third. Then the fourth. Each one a self-propelled contactdetonating warhead. Each one designed specifically to penetrate submarine hulls. Each one representing a technology that Mueller, despite 18 months of combat, did not know existed. He did not know it was called the Hedgehog.
He did not know it was a forwardthrowing mortar system that could attack without losing sonar contact. He did not know it could fire 24 projectiles in 60 seconds in a pattern designed to ensure at least one would strike any submarine within range. He only knew that he was dying, that his boat was dying, that his men were dying.
U672 sank in 94 seconds. Miller and 36 men reached the water as the boat slipped beneath the surface. The water was 3° C, brutally cold. Not cold enough to kill immediately, but cold enough that hypothermia would begin within an hour. Miller floated on a piece of wooden grating, his uniform saturated, his body already losing heat to the Atlantic.
Around him, the screams of dying men echoed across the water. HMS Oriel appeared first. The twler that had been coordinating the attack with the destroyer. They threw life nets into the water. Miller grabbed one. He pulled himself up. A British sailor seeing his German uniform helped drag him onto the deck.
20 minutes later, the other escorts recovered the remaining survivors. 36 men out of 48, 12, dead or missing. Miller found himself on the deck of HMS Sharpshooter wrapped in a British naval blanket, shaking from cold and shock. An older British officer approached him, Royal Navy Captain James McIntyre, commanding the escort group. McIntyre was not unkind.
Your boat was caught by our newest weapon, McIntyre said in German. We call it the Hedgehog. It’s a forward firing mortar system. When you attempted to surface for a night attack, we detected you on sonar. We fired 24 shaped charges in a geometric pattern. You never had a chance. Müller said nothing. He was trying to process what McIntyre was telling him.
A weapon system so new, so advanced that it could be deployed without losing sonar contact. A weapon system so devastating that it could transform a successful night attack into a catastrophe in 94 seconds. McIntyre continued, “This is the third Ubot we’ve sunk with hedgehog in 3 weeks. The message will reach your high command. The old rules of submarine warfare are finished.
Your boats can no longer hunt convoys on the surface at night. You can no longer use darkness as cover. We can see you, track you, and attack you without losing contact with our prey.” Miller understood. He understood with absolute clarity what McIntyre was saying. Every yubot commander in the Atlantic had believed that night surface attacks were the fundamental advantage of the submarine.
The escort could not see you. The convoy could not see you. Only your periscope needed to see them. This had been the doctrine for 3 years. But the hedgehog fundamentally changed that dynamic. Not through superior firepower, through superior system. A weapon that did not require losing sonar contact.
A weapon that did not rely on prediction or luck. A weapon that turned the Yubot’s traditional advantage. The ability to attack from darkness, from the unseen depths into a fatal vulnerability. Mueller realized something deeper. The hedgehog was not revolutionary because of its explosive power. Yubot had survived far more powerful depth charges.
The hedgehog was revolutionary because it fundamentally changed the relationship between attacker and defender. A yubot that chose to attack had to surface. A surfaced Ubot could be detected by sonar. A detected Ubot in May 1943 was a dead Yubot. The mathematics were simple and brutal. The advantage had shifted entirely to the escort.
That night, Miller sat in the captain’s cabin of HMS Sharpshooter, still shaking, and he realized something that would take the German Navy another month to understand. The Battle of the Atlantic had not been lost by shortage of hubot. It had not been lost by shortage of torpedoes or fuel or supplies.
It had been lost by a system of technologies working in perfect coordination. Hedgehog mortars, centimetric radar, highfrequency direction finding, escort carriers, sonar, coordinated convoy tactics. Each one was a piece of a comprehensive system. Together, they made operations unsustainable. The highfrequency direction finding could locate a yubot by its radio transmissions from hundreds of kilometers away.
The centimetric radar could detect a surfaced yubot at 30 km in any weather. The escort carriers provided aircraft that could drop depth charges or attack with guns. And when a yubot tried to defend itself by diving, the sonar could track it underwater while the hedgehog waited on the surface for the perfect moment to fire.
Each component made the others more effective. Sonar found you. Radar confirmed your position. Direction finding cut off your escape routes. Hedgehog prevented you from diving to safety. There was no counter tactic, no evasion, no way out. Admiral Donuts would not understand this. The German Naval High Command would not understand this.
They would interpret the collapse of the Yubot campaign in May 1943, Black May, when 43 Yubot were sunk and over 1,000 submariners died as a shortage of boats, not a failure of understanding. But Mueller, sitting in that cabin on May 24th, 1943, knowing that 36 men had been pulled alive from the water and 12 had died or vanished, Mueller understood the truth.
The weapon was not the hedgehog. The weapon was the system, and Germany had no answer for it. Bernhard Mueller spent 2 years in British and Canadian prisoner of war camps following the sinking of U672. He survived the war. He survived the peace. Müller described May 23rd, 1943 as the night when submarine warfare fundamentally changed.
Unlike most German commanders who blamed shortage of boats or lack of resources, Miller understood something deeper. We had believed that courage, training, and determination could overcome any disadvantage. The Hedgehog taught us that technology was not an enhancement to war. It was war itself. Every ship we built, every tactic we developed, every brave man we sent to sea, it could all be rendered obsolete overnight by an enemy system that was more advanced.
Miller’s insight was rare among German officers. Most attributed the Yubot losses to bad luck or insufficient resources. Miller understood it was systems. It was integration. It was the Allies ability to combine every technological advantage into one comprehensive anti-ubmarine warfare network that made individual courage irrelevant.
The Hedgehog was not revolutionary because of its explosives. It was revolutionary because it fundamentally changed the relationship between attacker and defender. A hubot that chose to attack had to surface. A surfaced Ubot could be detected by sonar. And a detected yubot in May 1943 was a dead yubot. Thank you for watching.