When Americans Captured This Nazi Sub Alive — They Found Hitler’s Secret Weapon

The Men Who Boarded a Sinking U‑Boat: How USS Pillsbury Pulled Off the Impossible

At 11:15 on the morning of April 9, 1944, Lieutenant Commander George Castleman stood on the bridge of the destroyer escort USS Pillsbury, watching a German submarine break the surface 700 yards off his starboard bow.

He had spent ten months hunting U‑boats. Dozens of sonar contacts. Dozens of depth‑charge patterns. Plenty of oil slicks and debris.

But never a capture.

The boat now forced into the daylight was U‑515, commanded by one of Germany’s most feared aces. Kapitänleutnant Werner Henke had sunk twenty‑five Allied ships. In December 1942, one of his torpedoes had sent the British troopship Ceramic to the bottom, taking more than 600 men, women, and children with her.

Now Henke’s luck had run out. Hours of depth charging by Pillsbury and her sisters had mangled his submarine. U‑515 burst out of the Atlantic trailing foam and oil, the bow heaving.

German sailors scrambled onto the deck. A few ran for the guns. Others simply jumped.

Castleman gave the order. Pillsbury opened fire. So did USS Flaherty and the other escorts. Machine‑gun bullets punched into the conning tower. Aircraft from the escort carrier USS Guadalcanal swept in low, rockets rolling across the water.

Within minutes, U‑515’s bow lifted toward the sky. She slid backward and disappeared.

Forty‑four German sailors were pulled from the water, including Henke himself. A dangerous U‑boat was gone. By every normal measure, it was a clean victory.

Captain Daniel Gallery, commanding Guadalcanal and the whole hunter‑killer group, saw something else.

He saw ten minutes.

That was how long U‑515 had wallowed on the surface before she finally sank. Ten minutes in which none of his ships had been prepared to try the unthinkable: board a live German submarine and take it as a prize.

In those ten minutes, Gallery realized, they might have seized everything the Allies had been bleeding for in the Atlantic: Enigma machines, current codebooks, torpedo technology, tactical orders. Instead, the boat and her secrets were gone.

The U.S. Navy had not captured an enemy warship at sea since 1815. For 129 years, doctrine had been simple: find, fix, destroy. There were no procedures for boarding enemy subs. No special training. No equipment. No one had even bothered to ask if it was possible.

Gallery decided it was time to ask.

And to prepare to answer yes.

Planning for the Impossible

The obstacles were obvious and deadly.

U‑boat crews were trained to scuttle their boats in minutes. The instant a captain decided his submarine was lost, he ordered demolition charges armed and sea valves opened. Explosives in key compartments would blow the hull apart. Flooding would do the rest. Codebooks were to be burned or weighted and thrown overboard. Enigma machines smashed. Anything secret destroyed.

Even if American sailors reached a surfaced U‑boat, they would be climbing onto a sinking, booby‑trapped hull.

Meanwhile, the logic of anti‑submarine warfare was brutal and simple. In 1943 alone, U‑boats had sunk more than 300 Allied merchant ships. Destroyer escorts like Pillsbury existed to talk with their sonar, attack with depth charges, and never give a submarine time to strike back. Every extra second a U‑boat remained afloat was another second it could fire.

There was no slack in that system for romantic notions of boarding parties.

Still, Gallery pushed ahead. Every ship in Task Group 22.3 was ordered to form a small, handpicked boarding team. They would train in secret. And the next time a U‑boat stayed on the surface, they would attempt something no living American sailor had ever done: storm an enemy sub under fire and keep it afloat.

Pillsbury’s team would be eight men, led by Lieutenant (j.g.) Albert David.

David was forty‑one, a career sailor who had worked up from enlisted man to engineering officer. He knew pumps, valves, hulls, and the thousand quiet ways ships could die if you failed to understand where the water was trying to go.

He knew nothing about boarding a hostile submarine.

No one did.

Six Weeks to Learn a U‑Boat

When Task Group 22.3 returned to Norfolk in late April 1944, Castleman called his chosen men together. He told them, in plain language, that they were going to board a German submarine if the chance came.

They had six weeks to figure out how.

Once Pillsbury sailed again on May 15, the fan‑tail became a makeshift training ground. Every day, David drilled his team.

They practiced climbing down nets into a small boat and back up onto a rolling hull. They rehearsed leaping from a whaleboat onto a moving deck. They studied captured photos and technical diagrams of German Type IX submarines until they could sketch the layout from memory: control room here, engine room there, forward and aft torpedo spaces, battery compartments, conning tower trunk.

The scenario they practiced was unforgiving. A damaged U‑boat would likely be circling out of control, its rudder jammed by depth charges. The deck would be slimy with oil and seawater. German survivors might still be aboard, armed and desperate. Demolition charges would be ticking down. Sea valves would already be open. The boat would be literally in the act of sinking while they climbed aboard.

David estimated they would have perhaps three to five minutes to arrest that process.

In that tiny window, his men would have to:

Find and shut the main flooding points.
Locate and disarm as many demolition charges as possible.
Keep the submarine from rolling or plunging under long enough to salvage her.

Their tools were simple: wrenches, flashlights, sidearms. There were no special “capture kits” for U‑boats. Those would come later. For now, they had to improvise.

While David and his team drilled, Gallery refined the bigger plan with his destroyer escort skippers. Once a U‑boat was forced up, escorts would deliberately limit their fire. Small‑caliber guns would rake the deck to drive German sailors overboard and keep them from manning weapons, but the ships were not to blast the hull full of holes. Aircraft could strafe the conning tower but were told to avoid hits at or below the waterline.

The goal was no longer just to kill U‑boats.

The goal was to wound one so badly that she could neither fight nor flee.

And then take her.

Contact

For weeks in late May and early June, Guadalcanal’s aircraft prowled the seas west of Africa, searching. Sonar operators sat hunched over their sets, listening for the elusive echo of a submarine hull.

Nothing. Days of nothing.

Then, on June 4, 1944, as Task Group 22.3 was turning north toward Casablanca to refuel, sonar aboard USS Chatelain picked up a contact: 800 yards away, dead ahead of the carrier.

A U‑boat was running submerged, unaware she was driving into the teeth of a hunter‑killer group.

Chatelain charged in and dropped a pattern of depth charges. Oil blossomed on the waves. Wildcat fighters overhead raked the surface with machine‑gun fire to mark the line of attack.

Six and a half minutes later, a gray shape lurched out of the Atlantic, bow first.

This time it was U‑505.

Her rudder was jammed. She began to circle helplessly at five or six knots, trailing water and oil. German sailors boiled out of the conning tower. One tried to reach a gun and fell, cut down by machine‑gun fire. The rest leaped into the sea with hands raised.

On Pillsbury’s bridge, Castleman saw the submarine’s track and did not hesitate.

“Lower the whaleboat.”

David and his men were already in their gear. As Pillsbury closed the range, the boarding party dropped over the side into the small boat. The coxswain gunned the engine and aimed directly for the circling submarine.

U‑505 was still moving, still settling by the stern. The whaleboat had to cut inside her turn and then match speed at the exact moment the hull slid past. Oil slicked the sea. German survivors splashed in the water, calling for rescue in desperate, foreign voices.

David ignored them. His mission, for now, was steel, not men.

The whaleboat thumped alongside. U‑505’s wet hull loomed above them, rising and dropping. David grabbed a railing, pulled himself up, and scrambled onto the U‑boat’s deck. One dead German lay facedown near the conning tower hatch.

The submarine rolled under his boots like a wounded animal.

He went down through the hatch.

Inside the U‑Boat

The control room was dim, lit only by red emergency lamps. Pipes hissed. Water sprayed from cracked fittings. The deck was already slanting noticeably aft.

The Germans had done their job well: sea valves open, charges planted.

David could hear the Atlantic forcing its way in.

He shouted for his men to spread out. One found an open sea strainer — a large intake for cooling water — its cover discarded. He located it nearby and spun it back on, slowing the worst of the flooding. Others began searching for demolition charges. They found them tucked behind panels, mounted on bulkheads, set into corners: thirteen in all, each with a fuse or time pencil designed to blow the submarine apart minutes after abandonment.

Working in ankle‑deep water, surrounded by machinery labeled in a language they could not read, David’s team pulled detonators, cut wires, and tossed impotent charges into a growing pile.

Above, U‑505’s wild circling brought her dangerously close to Pillsbury herself. At one point the captured submarine’s bow swung into the destroyer escort, crushing the whaleboat that had delivered the boarding party and flooding several compartments aboard Pillsbury.

Below, in the cramped steel coffin, David’s men stayed at their work.

They could feel the hull shudder with each impact. They kept closing valves.

By the time a second boarding team, led by Guadalcanal’s chief engineer, Commander Earl Trosino, arrived, U‑505 was still afloat.

Barely.

Trosino crawled through flooded compartments, tracing intact and broken pipes by hand. He identified which pumps still worked, which tanks could be blown dry, where patches were needed most. Slowly, the submarine’s frantic settling eased. The bow rose a little. The stern stopped sinking quite so fast.

The impossible had happened.

An American boarding party had taken control of an enemy submarine that was supposed to be unsalvageable — and kept her from going under.

Silence and Consequences

The technical haul was staggering.

In the hours that followed, crews hauled out two complete Enigma cipher machines with rotors in place, stacks of current codebooks and operational orders, patrol charts mapping U‑boat hunting grounds, and two acoustic homing torpedoes of a type the Allies had never examined.

The intelligence impact would ripple from the Atlantic to Bletchley Park to the Normandy beaches.

But only if the Germans never realized what had happened.

Gallery ordered total silence. No mention of the capture in any log. No radio signals describing the event. The fifty‑eight German survivors were kept isolated. Their families were told they were missing, presumed dead. The submarine herself was towed thousands of miles in secret to Bermuda, repainted, and hidden.

The risk had been enormous. If word leaked, the German Navy would change its codes overnight. Months of decrypts would vanish. U‑boat deployments would become invisible again just as Allied ships were crossing to France in massive invasion convoys.

No one talked. Three thousand American sailors kept their mouths shut.

The Germans never knew. Admiral Karl Dönitz, master of the U‑boat fleet, simply added U‑505 to a long list of boats “assumed lost to enemy action.”

Meanwhile, British codebreakers used the captured material to sharpen their reading of German messages. American ordnance engineers dissected the acoustic torpedoes and developed decoys that lured the weapons away from ships.

A boarding party of eight men, scrambling into a crippled U‑boat under fire, had helped turn mathematics and mechanics decisively against the German submarine arm.

Today, visitors to the Museum of Science and Industry in Chicago can walk through U‑505, preserved almost exactly as she looked on that June day in 1944. They can see the narrow control room where David’s flashlight beam first caught the glint of wiring on a demolition charge, the valves Trosino’s hands found in cold, oily water.

They see steel and gauges and cramped bunks.

What they cannot see, but what the story reveals, is the thin layer of decision that separates “standard procedure” from “something new.” Gallery choosing to train boarding parties. Castleman choosing to lower the whaleboat. David choosing to go down the hatch of a sinking, possibly booby‑trapped submarine.

Those choices, made in days and seconds, turned a routine U‑boat kill into one of the most valuable captures of the war — and proved that even in a conflict dominated by mass production and code machines, eight men with wrenches, pistols, and nerve could still change everything.