SMS U-21

Survived

Type	Submarine
War	First World War
Main guns	4 × 50 cm (19.7 in) torpedo tubes

Under Otto Hersing she sailed from Germany round Spain to the Mediterranean and sank Triumph and Majestic off Gallipoli in May 1915.

German submarines at Kiel, Schleswig-Holstein, on 17 February 1914. Identifiable are: U 22, U 20, U 19, and U 21 (first row, left-right); U 14, U 15, U 12, U 16, U 18, U-17, and U 13 (second row, left-right); U-11, U-9, U-6, U-7, U-8, and U-5 (third row, left-right). As U 22 (the newest boat) was co Photo: Bain News Service, Public domain · Wikimedia Commons

Armament and specifications

Armament

4 × 50 cm (19.7 in) torpedo tubes
1 × 8.8 cm (3.5 in) SK L/30 gun (from 1916 2 ×)

Builder	Kaiserliche Werft Danzig
Laid down	27 October 1911
Launched	8 February 1913
Commissioned	22 October 1913
Displacement	650 t (640 long tons) surfaced 837 t (824 long tons) submerged
Length	64.15 m (210 ft 6 in)
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

As built, from the ship's Wikipedia article. Figures there may cover later refits too.

Career

Launched

8 February 1913

U-21 off Gallipoli

Survived

25–27 May 1915

Otto Hersing

Fate

Survived

Returned to Imperial German Navy command