SM U-21 (Germany)

SM U-21 (right-hand end of first row)
History
German Empire
Builder:	Kaiserliche Werft Danzig
Laid down:	1910
Launched:	8 February 1913
Commissioned:	22 October 1913
Fate:	Sunk accidentally, 22 February 1919
Austria-Hungary
Name:	SM U-36
Commissioned:	21 September 1915
Decommissioned:	1 October 1916
Fate:	Returned to Imperial German Navy command
General characteristics
Class and type:	German Type U 19 submarine
Displacement:	650 t (640 long tons) surfaced 837 t (824 long tons) submerged
Length:	64.15 m (210 ft 6 in)
Beam:	6.10 m (20 ft)
Height:	8.10 m (26 ft 7 in)
Draft:	3.58 m (11 ft 9 in)
Propulsion:	2 shafts 2 × MAN 8-cylinder two stroke diesel engines 2 × AEG double Motordynamos
Speed:	15.4 knots (28.5 km/h; 17.7 mph) surfaced 9.5 knots (17.6 km/h; 10.9 mph) submerged
Complement:	4 officers, 25 men
Armament:	4 × 50 cm (19.7 in) torpedo tubes 1 × 8.8 cm (3.5 in) SK L/30 gun (from 1916 2 ×)
Service record
Part of:	German Imperial Navy: III Flotilla 1 August 1914 – 5 June 1915 Constantinople Flotilla 5 June 1915 – unknown end Pola Flotilla Unknown start – 4 March 1917 III Flotilla 4 March 1917 – 11 November 1918
Commanders:	Kptlt. Otto Hersing 22 October 1913 – 31 August 1918 Kptlt. Friedrich Klein 1 September – 11 November 1918
Operations:	11 patrols
Victories:	36 merchant ships sunk (79,005 GRT) 2 merchant ships sunk (8,918 GRT) 4 warships sunk (34,575 tons)

SM U-21 was a U-boat built for the Imperial German Navy shortly before World War I. The third of four Type U-19-class submarines, these were the first U-boats in German service to be equipped with diesel engines. U-21 was built between 1910 and October 1913 at the Kaiserliche Werft (Imperial Shipyard) in Danzig. She was armed with four torpedo tubes and a single deck gun, though a second was added during her career.

In September 1914, U-21 became the first submarine to sink a ship with a self-propelled torpedo when she destroyed the cruiser HMS Pathfinder off the Firth of Forth. She also sank several transports in the English Channel and the Irish Sea later in the year, all in accordance with the cruiser rules then in effect. In early 1915, U-21 was transferred to the Mediterranean Sea to support the Ottoman Empire against the Anglo-French attacks during the Gallipoli Campaign. Shortly after her arrival, she sank the British battleships HMS Triumph and HMS Majestic while they were bombarding Ottoman positions at Gallipoli. Further successes followed in the Mediterranean in 1916, including the sinking of the French armored cruiser Amiral Charner in February.