SM U-21 (Germany)

SM U-21 was one of the most famous U-boats to serve in the Imperial German Navy in World War I. She was the first submarine to sink a ship with a self-propelled torpedo. She also sank the British battleships HMS Triumph (1903) and HMS Majestic (1895). U-21 survived the war and sank while under tow by a British warship in 1919.

Outbreak of War
Ordered in 1911 and built by the Imperial Shipyard in Danzig, U-21 was commissioned in 1913. In August 1914 at the outbreak of war, she was stationed at Heligoland, as part of the Third Half Flotilla (Second Flotilla). She was commanded by Otto Hersing, who stayed with her until the end of the war. On her third war patrol, she sighted the Royal Navy scout cruiser, HMS Pathfinder (1904) off the coast of St Abbs Head in Scotland, on 5 September 1914. A single torpedo hit the cruiser's hull causing a boiler explosion which in turn ignited the ship's magazine. Pathfinder sank within four minutes and only 18 of her crew of 268 survived. This was the first ship to be sunk by a submarine-launched self-propelled torpedo - the USS Housatonic (1861) had been sunk in 1864 with a spar torpedo, a simple charge fixed to a pole. U-21 was also the first U-boat to enter the Irish Sea. On 29 January she shelled the airship sheds on Walney Island off Barrow-in-Furness, but was driven off by shore batteries.



In the Mediterranean 1915-17
On 5 June 1915, U-21 was transferred to the Mediterranean Sea to support Germany's ally, Turkey. During this voyage, she evaded air attack in the Strait of Gibraltar and became the first U-boat to enter the Mediterranean and the first submarine to refuel at sea. Arriving off Galipoli on 25 May, she sighted the pre-Dreadnought battleship, HMS Triumph, which was at anchor bombarding Turkish coastal artillery at Gaba Tepe. Approaching to within 300 metres, Hersing fired a single torpedo, which penetrated the Triumph's torpedo nets and then her hull. She began to list and capsized within 10 minutes; 73 of her crew of nearly 600 were lost. Most of the British and French battleships were withdrawn, but two days later, it was felt that it would be safe for HMS Majestic to resume the bombardment, close inshore and surrounded by transport ships and torpedo nets. U-21 fired two torpedoes through a gap in the barricade and the Majestic quickly sank; 40 of her crew were lost. The U-boat had been spotted by an RNAS aircraft flown by Wing Commander Samson which made several bombing runs. Hersing escaped by diving under the French battleship Henri IV; when the U-boat reappeared later, Samson had run out of bombs and could only fire his rifle at her.

U-21 retired to İstanbul. On 4 July she sank the French transport ship Carthage and then made her way into the Adriatic Sea, where she joined the Deutsche U-Flotilla Pola, based at Cattaro. From 21 September 1915 until 16 October 1916 she was flying the flag of the Austro-Hungarian Navy, which assigned her the number U-36. On the 8th February 1916, she sank the French armored cruiser Amiral Charner off the Syrian coast.

End of the War
In March 1917 she joined the High Seas Fleet in Kiel. The U-21 survived the war and still under Hersing's command, accidentally sank on 22 February 1919 in the North Sea while under tow by a British warship. Some accounts maintain that she was scuttled by Hersing, who took up potato farming after the war. During the war, U-21 sank a total of 40 Allied ships (113,580 tons) and damaged two further ships (8,918 tons).