For more information about discovery of this submarine, please see theĀ North Sea and English Channel Hunt page.

Story of the U-21

One can almost hear the sound of a U boat doggedly tailing an unsuspecting battleship, preparing for the kill. It’s the kind of music one would hear in JAWS or some other action thriller, the pictures are so clear in our collective memory. But the stories of the U-boats are true.


Clive Cussler, founder of the National Underwater & Marine Agency, relates the history of the U21, the most famous of all the U boats Germany launched at the Allies in what came to be known as World War I.

Commanded by Captain Otto Hersing throughout the entire war, U21 was part of the third Half Flotilla (2nd Flotilla) stationed in Heligoland at the outbreak of war in August, 1914. The U-boats were stationed there in anticipation of an Allied naval drive into the Heligoland Bight, which failed to materialize.

U21’s first war patrol began on 8th August and was designed to intercept Royal Navy warships escorting troop convoys to France, it was curtailed after U21 was forced back to base by adverse weather conditions. A second unsuccessful repeat of this patrol lasted from 15th to 19th August, this time no targets presenting themselves for U21.

It was during the boat’s third patrol while patrolling North of St. Abbs Head in search of Royal Navy targets that Hersing stumbled across HMS Pathfinder patrolling the Scottish North Sea Coast. A single bow torpedo fired at a range of 1600 yards pierced the cruiser’s flank, puncturing and igniting a boiler. This in turn sprayed red-hot shrapnel through the bulkhead into the ship’s magazine. The resultant explosion sank HMS Pathfinder* within four minutes, only 11 of her crew surviving. This was the second ship ever sunk by a submarine, and the first in which the attacking submarine successfully escaped. (*Clive Cussler and NUMA also discovered the HMS Pathfinder in 1984.)

On 5 June 1915 U21 was transferred to the Mediterranean to be based at Constantinople as part of the U-Mittelmeer Division eventually alongside four UB boats and three UC minelayers (transferred overland by rail). In doing so U21 became the first U-boat to ever penetrate the Mediterranean and also the first submarine to refuel at sea near Spain. Although spotted by aircraft near Gibraltar during his transit of the narrow Straits, Hersing made landfall on 13 May at Cattanro, before making repairs and completing his journey towards Gallipoli.

Hersing made his presence felt to the Royal Navy on 25 May at noon. After two hours stalking the battleship HMS Triumph near Gaba Nepe, which was engaged in bombarding Turkish shore positions, a single torpedo passed through the ship’s anti-submarine nets and ripped a hole in her side. The ship capsized before going under. Hersing again escaped, this time by diving under the capsized wreck before it sank.

Two days later U21 sank another battleship, HMS Majestic, off Cape Helles. Another single torpedo after hours of patiently waiting for the correct moment to strike and the battleship went down in 150 feet of water. This time Hersing suffered some retaliation, Air Commodore

Swanson circling above in his flimsy aircraft spotted the U-boat and dropped several hand held bombs before U21 escaped by diving under the French battleship Henry IV and making for the Dardanelle’s. Swanson again detected the U21 later in the day when Hersing had surfaced, but the British aircraft had no more bombs left to throw.

Hersing only made one more sortie from Constantinople, emerging to sink the French transport Carthage on July 4th, before proceeding to the Adriatic after finding his return route to Turkey blocked. Once in the Adriatic, U21 was transferred to the Deutsche U-Flotilla Pola, based at Cattaro. Later Hersing returned to the North Sea, joining the IIU-Flotille, High Seas Fleet, on March 4, 1917.”

U21 survived the war and was due to be handed over to the Royal Navy, sailing from Kiel to Harwich after the Armistice had been signed. While under escort, Hersing ordered the boat’s valves opened and despite British attempts to prevent it’s sinking, U21 was successfully scuttled in the North Sea. During her career she had sunk 36 ships for 78,712 tons.

The U21 is mainly remembered as the first submarine to sink an enemy ship and survive. The first submarine to sink an enemy ship, of course, was the CSS Hunley, also discovered by Clive Cussler and NUMA.

The U21 was ordered in 1911 and commissioned in 1913. She was built by Kaiserliche werft at the Imperial shipyard in Danzig. Her displacement was 650 tons surfaced; 837 tons submerged. The boat’s length was 210.476 feet and her beam was 20.01 feet. Compare that to the Hunley which was less than 40 feet long and less than five feet across. In 47 years, submarine design had come a long way but as more is learned from the Hunley, one is amazed at her modern design. For more information on the Hunley please go to www.hunley.org.

4 Responses to U-21

  1. Hucklepickleberry says:

    My children’s Great Great Great Uncle was one of the 78 sailors on HMS. Triumph who lost their lives when the ship was sunk by U21. Victor Ernest Funnell, aged 22 years, 5ft. 4ins. from Southwick, Sussex.

  2. Linda says:

    First, let me say, I have read many of your books and thoroughly enjoyed them. Such adventures!!

    Whenever I come across an article about the German U-boats, particularly during WW I, I read it with interest. I do family research and my dad’s cousin told a story about a brother of his mother’s who was rumored to have died on a submarine. His mother was my grandfather’s sister. I don’t have verification. When I inquired of some German military historical organization they wanted information I don’t have to look. However, my grandfather’s brother came to this country shortly after he did and was here in Sept. of 1907 because he was a witness at my grandparents’ marriage. After that I can’t find any trace of him until I ran across a picture of some plaques honoring war dead that are hanging in the Petersdorf church on Insel Fehmarn, so he did die in WW I. I may never know if the rumor about death on a submarine is true.

  3. Alan Rockey says:

    Fantastic information my Grandad Harry Hansford was on board HMS Majestic when it was torpedoed, he survivied and spent the rest of the war on DAMS sailing across the Atlantic ocean. Thanks for the information

  4. Fascinating insight into the wartime exploits of the U-21….mention of which will feature in this weekends guided walk in Brockley & Ladywell cemeteries ( Open Day) as one of the victims of the HMS Pathfinder sinking is Bernard Harry Leopold Thompson who is remembered on a family headstone.


    Mike Guilfoyle
    Vice-Chair : Foblc

Leave a Reply

Your email address will not be published. Required fields are marked *