German submarine U-21 (1936)

German submarine U-21 was a Type IIB U-boat of the Nazi German Kriegsmarine. Her keel was laid down 4 March 1936, by Germaniawerft of Kiel as 'werk' 551. She was commissioned on 3 August 1936. During World War II, she conducted operations against enemy shipping.

U-21 went on seven war patrols, sinking five ships, one auxiliary warship and damaging one warship.

1st, 2nd and 3rd patrols
U-21's first patrol was relatively uneventful.

On her second foray, the boat was attacked by the British submarine HMS Ursula which fired six torpedoes at her in the North Sea northeast of Berwick-Upon-Tweed [On the English/Scottish border] on 17 September 1939. These were the first submarine weapons launched by the Royal Navy in the Second World War. They all missed.

On her third patrol, the U-boat also had torpedoes fired at her in the central North Sea by another British submarine, HMS Sealion. The result was inconclusive as well.

4th and 5th patrols
The boat's first success with a torpedo came on 1 December 1939 when she sank the Finnish-registered Mercator about 12 mi southeast of Buchan Ness (near Peterhead). She also damaged the British cruiser HMS Belfast with a mine.

On her fifth sortie, she sank the Mars on 21 December 1939 and the Carl Henckel (both from Sweden), on the same day. She also sank the British boom defence vessel HMS Bayonet in the Firth of Forth, again with a mine.

6th patrol
Patrol number six saw her sink the Danish Vidar 100 mi east of the Moray Firth on 31 January 1940.

7th patrol
She sank the British Royal Archer with a mine on 26 February 1940, but then it all went horribly wrong on 26 March when she ran aground off Oldknuppen Island after a navigational error. The boat was towed to Mandal in Norway where she was interned. She was then towed to Kristiansand for repairs and release after the German occupation of the Nordic country.

Fate
In July she was transferred to the 21st U-boat Flotilla in Kiel as a training boat, with whom she remained for the rest of the war. U-21 was scrapped in February 1945.