A First Patrol — and a Last

The German submarine U-550 was on her very first war patrol.

So was her commander, Klaus Hänert, a young and determined officer entrusted with his first command at a moment when Germany’s U-boat arm was already fighting for survival.

The Atlantic was no longer friendly to submarines.

By 1944, every patrol carried the weight of near-certain danger. Crews knew that chances of return were slim. Still, orders were orders, and U-550 slipped into position off the American coast,

roughly seventy nautical miles southwest of Nantucket, east of New Jersey.

There, Hänert found his target.

The Pan Pennsylvania loomed like a steel island, her silhouette unmistakable even in poor visibility. Laden with fuel, she was a prize worth the risk. One well-placed torpedo could cripple Allied supply lines, even briefly.

Hänert did not hesitate.

One Torpedo, Catastrophic Consequences

At the chosen moment, U-550 fired a single torpedo.

It struck the tanker on her port side with brutal precision.

The explosion tore into the hull, igniting fires and sending shockwaves through the massive vessel. Compartments collapsed. Fuel ignited. Metal screamed and twisted. The damage was devastating, and the time between impact and evacuation was heartbreakingly short.

Fifteen of the Pan Pennsylvania’s fifty merchant sailors were killed almost instantly.

Below decks and on exposed gun stations, ten of the thirty-one United States Navy Armed Guard personnel also lost their lives.

For those who survived the initial blast, chaos ruled. Smoke choked passageways. Firelight reflected off oil-slicked water. Orders were shouted, drowned out by the roar of flames and the hiss of escaping steam.

Yet the tanker did not sink immediately.

And above the waves, her escorts were already closing in.

The Hunters React

The convoy’s protection responded without hesitation. Three destroyers surged toward the attack position:

Two of them were crewed by the United States Coast Guard, a reminder of how fully America’s maritime services had merged in wartime necessity.

For Klaus Hänert, escape options collapsed almost instantly.

In a daring—and desperate—move, he maneuvered U-550 directly beneath the wounded Pan Pennsylvania, attempting to hide beneath her massive hull. The logic was sound in theory The tanker’s wreckage might confuse sonar. The noise of burning fuel and collapsing metal could mask the submarine’s presence.

For a few tense moments, it almost worked.

But Allied anti-submarine warfare had evolved too far.

USS Joyce detected the submarine.

And then the sea exploded.

Depth Charges and Desperation

Depth charges rolled into the water, detonating with thunderous force. Shockwaves slammed into U-550’s hull, crushing valves, rupturing systems, and flooding compartments. Inside the submarine, lights shattered. Men were thrown from their stations. Water poured in through damaged seals.

The boat shuddered, wounded beyond recovery.

Hänert knew the truth immediately.

Escape was no longer possible.

There would be no silent withdrawal into the depths. No slipping away into darkness.

Only one option remained.

A Surfacing Under Fire

Hänert ordered U-550 to surface.

It was a command few U-boat captains ever gave willingly. Surfacing under escort fire was often a death sentence. But standard procedure dictated one last act of resistance—to buy time for scuttling charges to be set and the Enigma cipher destroyed.

As the submarine broke the surface, she emerged into a storm of gunfire.

Hänert ordered his crew to man the deck guns.

What followed was brief, violent, and utterly one-sided.

USS Gandy closed in and rammed the submarine, steel striking steel with bone-shaking force. Gunfire tore across U-550’s deck. Shells punched into the conning tower. Joyce added her fire, saturating the area with explosions and tracers.

USS Peterson delivered the final blows, ensuring the submarine could not escape or remain afloat.

Amazingly—and almost unheard of—the submarine’s final moments were captured on camera. Photographs show U-550 on the surface, her crew scrambling, leaping into the sea as the boat began to slip beneath the waves.

Cold Water, Fading Chances

Most of U-550’s crew escaped the hull.

But the Atlantic in April was unforgiving.

Hypothermia claimed men quickly. Wounds slowed others. Oil slicks clung to uniforms, weighing them down.

Only twelve men survived.

Among them was Klaus Hänert.

The rest—experienced sailors and young recruits alike—vanished beneath the waves, their first patrol becoming their last.

U-550 slipped under, taking her secrets with her.

Survivors, Memory, and an Unexpected Friendship

War rarely leaves room for sentiment.

Yet in the aftermath, something remarkable occurred.

After the conflict ended, Klaus Hänert formed a lasting friendship with the captain of USS Joyce—the very ship that had hunted and destroyed his submarine. The two men corresponded, shared memories, and eventually met in the United States.

It was not forgiveness or guilt that bound them, but recognition.

Recognition of shared danger.

Shared responsibility.

Shared survival.

In a war defined by ideology and destruction, this quiet human connection stood apart—a reminder that those who fought often understood one another better than those who commanded them.

A Wreck Lost — Then Found

For decades, U-550 lay undiscovered on the seabed.

Charts marked the general area. Reports described her sinking. But the ocean kept her hidden.

Until 2012.

That year, a group of amateur divers and history enthusiasts located the wreck. There she lay, silent and intact, a steel time capsule preserving the final chapter of a forgotten battle.

The discovery renewed interest in the story—not as a tale of victory or defeat, but as a moment frozen in time.

One torpedo.

One convoy.

One brief, violent encounter in the vast Atlantic.

A Small Battle With Lasting Echoes

The attack on the Pan Pennsylvania did not alter the course of the war. Fuel continued to flow. Convoys kept sailing. The Allies advanced toward victory.

But for the men involved, the encounter was everything.

For the tanker’s crew, it was a sudden descent into fire and loss.

For the escorts, it was proof that vigilance still mattered, even late in the war.

For Klaus Hänert and U-550, it was the beginning and the end, compressed into a single day.

The Atlantic swallowed the evidence, but not the memory.

Today, the photographs, the wreck, and the stories allow us to see beyond statistics and tonnage. They reveal war as it truly was at sea—brief, brutal, and profoundly human.

On 16 April 1944, just one day out of New York, the Pan Pennsylvania and U-550 crossed paths.

Neither crew knew it then.

But that meeting would echo across decades, reminding us that even in the vastness of the ocean, history can turn on a single torpedo.