The biting April wind sends dark waves over the submarine. Until now, the spring of 1917 has been unusually cold.

They are far from land, but Captain Heinrich Stenzler knows that he will soon have German soil beneath his feet on the island of Heligoland west of Denmark.

He has chosen the safe route home and is sailing closer to the Danish west coast than planned in order to avoid the British naval mines that fill the North Sea.

But what he doesn't know is that a few days previously, the British Royal Navy had laid a new mine field off the west coast. In the middle of the passage through which he is about to guide his 26-man crew.

This is the story of Captain Johan Heinrich Wilhelm Maximilian Stenzler and the final voyage of the UC-30. The last of the sunken German submarines from World War I, which, it appears, has now been found.

The First World War (1914-1918) is well known for the bloody and exhausting trench warfare on the Western Front. But a war was also being fought in the waters of the North Sea, a war that cost the lives of thousands of soldiers and civilians.

The British Navy is both bigger and stronger than that of the Germans. However, with the use of submarines and sea mines the Germans are able to match the British.

Submarine warfare is regarded as both devious and ungentlemanlike, but after losing several warships and merchant vessels to the Germans, the British decide to 'fight fire with fire'.

With 45,000 sea mines in the German Bight and off the west coast of Jutland and 70,000 sea mines in the Skagerrak, the sea becomes transformed into a veritable death trap.

Captain Heinrich Stenzler finds himself caught in the midst of this war. He has made a career in the German Navy since, at the age of 19 in 1905, becoming a sea cadet.

In 1915 he chooses to join the German submarine fleet, where he is quickly promoted to captain. The UC-30 is the first submarine he has under his command.

On 30 March 1917, the UC-30 sets out on its fourth voyage. Its task is to lay sea mines to the south of the Irish coast as part of a blockade of British merchant shipping.

"Don't expect to hear from me for the next four weeks." In order to placate his mother at home in Germany, Stenzler writes in a letter shortly before departure, "There's no need to worry,

the mood is good." The German struggle against the British warships and merchant ships has proved effective, and there's a sense that victory is within reach.

So even though the German submarine warfare is regarded as cowardly and contrary to good practices governing warfare, they continue undeterred.

Heinrich Stenzler himself is thrilled to be a part of the submarine fleet, something he makes no secret of in his letters home.

Not only has he been involved in laying sea mines, he has also been responsible for the UC-30 having sent two British warships and a Norwegian ship to the bottom.

Stenzler feels that in the submarine fleet he is making a difference. Here he can be permitted to fight at the front line, where he is sure that the war will be won.

"I hope that here I will finally be allowed to achieve something great," he wrote to his mother.

On course for Ireland, the UC-30 sails from Heligoland through the English Channel. It slips between minefields under the threat of the British.

On 4 April 1917 the submarine passes the British steamer Hunstanton. A merchant ship heading for London with a large cargo of wheat, and the perfect target for one of the UC-30's torpedoes.

The UC-30 dives to safety below the surface, only its periscope protruding, so that the submarine's commander is able to see Hunstanton's position.

At a weight of almost one and a half tonnes, a length of around seven metres and 200 kilograms of explosives in the nose section, it is a minor feat to launch a torpedo below sea level.

The crew can control which direction they send the torpedo. Whether or not it hits its target depends on the flow and the speed of the target.

The British merchant ship's location is checked once again before the torpedo is sent in the direction of the over 4,000 tonne steamer.

Now the crew of the UC-30 can do nothing but wait.

The torpedo hits its target. It is the fourth ship Stenzler sends to the bottom as captain of the UC-30 And this is far larger than the others.

But as Hunstanton goes to the bottom and the crew of the merchant ship brought to safety, the machinery in the 40 metre, 400 tonne submarine begins to fail.

One diesel engine is completely out of function, and there are also problems with the other. There is nothing for it but to return to base at Heligoland.

Anything else could be fatal.

The only way home is north of the British Isles. The UC-30 cannot return via the English Channel, because it is too dangerous.

But Stenzler estimates that with their 20-day supply of diesel fuel, they should be able to reach base on Heligoland despite, due to the damaged engine, having to sail more slowly than usual.

The mine chambers still hold the 18 sea mines that the UC-30 was loaded with before departure.

But instead of doing as others in the same situation have done before him - discarding the sea mines and heading for home - Captain Stenzler decides that the mines must be returned so that they can be used on a new expedition.

With the British at their heels, Stenzler and the UC-30 embark on the journey home.

As the steamer, Hunstanton is going down, the British Navy get wind of the German submarine, and a fleet of destroyers is sent out to send the UC-30 to the bottom.

But Stenzler does not maintain much radio contact with the base on Heligoland, making it difficult for the British to track him and the UC-30

Nevertheless, the British sail off along the northern route that they reckon Stenzler has taken.

On 14 April 1917 the UC-30 has made it north of the little island of North Rona, not far from the Shetland Islands north of Scotland.

Despite gales from the north, the UC-30 is sailing mainly on the surface. It is risky. When they are above the water, they are openly visible to the enemy, but it is impossible to be constantly submerged.

This is where the British spot them, and quickly set out after the submarine. Stenzler quickly orders the UC-30 to dive, and it comes as a surprise to the British.

Reports had stated otherwise, that the German submarine couldn't dive because of the engine problems. But it could, and Stenzler is able to get the crew safely below the surface.

The UC-30 has been at sea for nearly three weeks now.

In the three weeks it has not been possible for either Heinrich Stenzler or the crew to have a bath.

Baths are not a luxury to be enjoyed on a submarine, and as the weeks pass, the air becomes a rank mixture of sweat, diesel, cooking odours and stuffiness. But no one in the crew pays any attention to this. They all smell the same.

The aisles in the UC-30 are narrow, the ceiling is low, and the constant noise from the diesel engines form the background music to life aboard the UC-30 But just like the smell, the noise becomes an unremarkable part of everyday life.

It's been a long time since Heinrich Stenzler and his crew were able to get their teeth into fresh food.

The fresh supplies have long since run out. Now there is only preserved food, and it is the job of the ship's cook to prepare the food to the best of his ability in the submarine's tiny galley.

Half of the crew sleeps while the other is on duty. In this way, the distribution is quite natural when there are only half as many berths as crew members.

The hammocks are strung out, where there is space, between dining areas, luggage and spare ammunition.

The only place to find any kind of peace and quiet, and not least fresh air, is in the submarine's conning tower. When the boat is above water, the conning tower is a window to the outside world and a strategic observation post. But there's never really time to enjoy the fresh air.

The crew is constantly on guard. Constantly ready to dive beneath the surface if a British ship should come into view.

On 19 April 1917, the base on Heligoland receives a message from Heinrich Stenzler. The UC-30 is located 75 nautical miles west-southwest of Lindesnes Lighthouse on the south coast of Norway.

The UC-30 is ready to sail south towards Heligoland along 'Weg Blau', which is the safe way home through the minefields, reports Heinrich Stenzler.

This is the last radio contact that the base on Heligoland has with the submarine.

On 20 June 1917 a body is washed ashore north of Søndervig in Sonder Nissum Parish on the west coast of Jutland. It is Heinrich Stenzler.

The captain and his crew never reach Heligoland. On the way south they hit a British mine.

Heinrich Stenzler is in the submarine's conning tower with Sergeant Heinrich Carstens and Sergeant Reinholdt Meissner. They are the only ones flung clear of the boat, while the rest of the crew sinks to the seabed along with the submarine and the 18 sea mines.

And after two months in the dark waters, the three bodies are washed ashore on the west coast of Denmark. Stenzler and Carstens north of Søndervig and Meissner north of Esbjerg.

It's not something that arouses much attention. Dead sailors on the beach are not a rarity during the First World War.

There are numerous victims of battles at sea during the war and the west coast of Jutland is the natural final destination for those ending their days in the waters of the southern part of the North Sea.

Meissner and Carstens are buried in the churchyard at Ny Sogn not far from Søndervig.

Captain Stenzler is buried in Sonder Nissum parish, but later, at the request of relatives, is moved to his home town in eastern Germany, where he is reinterred.

The submarine war between Britain and Germany lasted until the end of the First World War in November 1918, when the Central Powers headed by the German Empire, surrendered.

During the war Germany produced 375 submarines. 178 of them were lost at sea and with them 5,000 men. The British, however, lost 5,000 ships to sea mines and submarine attack. Here, the vast majority were merchant ships.

Despite the fact that Denmark was neutral during the war, 305 Danish ships went to the bottom and more than 700 sailors lost their lives - partly because of German and British mines in the trade routes between Denmark and England.


Text: Karen Lerbech

Research: Simon Leth Stolzenbach, DR Arkiv

Graphics og animation: Morten Fogde Christensen

Video: Dennis Normann

Topvideo: Zangs Films / Shutterstock

Webdok editor: Hans Christian Kromann

Sources: The reconstruction of UC-30's last mission is build on old letters, logbooks, articles and interviews with Søren Nørby, Institute for Military History and War Studies at the Royal Danish Defence College , Poul Grooss, former naval officer and military historian at the Royal Danish Defence College and Gert Normann Andersen, Sea War Museum.

'British Merchant Ships Sunk by U-boats in World War One' by A. J. Tennent,
'From Imperial Splendour to Internment: The German Navy in the First World War' by Nicolas Wolz,
'U-boat Hunters: Code Breakers, Divers and the Defeat of the U-boats, 1914-1918' by Robert M. Grant,
'Dansk vejr siden 1874' by John Cappelen and Bent Vraae Jørgensen.

Websites:,, Onlineproject Gefallenendenkmäler.

Published: August 18th, 2016.