|Ordered:||7 December 1940|
|Laid down:||30 January 1942|
|Launched:||1 October 1942|
|Commissioned:||14 November 1942|
|Fate:||Sunk in January 1944 by a British aircraft|
|Class and type:||Type VIIC submarine|
|Height:||9.60 m (31 ft 6 in)|
|Draught:||4.74 m (15 ft 7 in)|
|Complement:||4 officers, 40–56 enlisted|
The submarine was laid down on 30 January 1942 at the Friedrich Krupp Germaniawerft yard at Kiel as yard number 661, launched on 1 October, and commissioned on 14 November under the command of Kapitänleutnant Wolfgang Wenzel.
After training with the 5th U-boat Flotilla at Kiel, U-231 was transferred to the 3rd U-boat Flotilla on 1 May 1943 which was based at La Pallice in France, for front-line service. In three war patrols, the U-boat sank or damaged no merchant ships. She was a member of eleven wolfpacks.
U-231 was sunk on 13 January 1944 in the North Atlantic northeast of the Azores by a British aircraft.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-231 had a displacement of 769 tonnes (757 long tons) when at the surface and 871 tonnes (857 long tons) while submerged. She had a total length of 67.10 m (220 ft 2 in), a pressure hull length of 50.50 m (165 ft 8 in), a beam of 6.20 m (20 ft 4 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.74 m (15 ft 7 in). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2,800 to 3,200 metric horsepower (2,060 to 2,350 kW; 2,760 to 3,160 shp) for use while surfaced, two AEG GU 460/8–27 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged. She had two shafts and two 1.23 m (4 ft) propellers. The boat was capable of operating at depths of up to 230 metres (750 ft).
The submarine had a maximum surface speed of 17.7 knots (32.8 km/h; 20.4 mph) and a maximum submerged speed of 7.6 knots (14.1 km/h; 8.7 mph). When submerged, the boat could operate for 80 nautical miles (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 8,500 nautical miles (15,700 km; 9,800 mi) at 10 knots (19 km/h; 12 mph). U-231 was fitted with five 53.3 cm (21 in) torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm (3.46 in) SK C/35 naval gun, 220 rounds, and an anti-aircraft gun. The boat had a complement of between forty-four and sixty.
U-231 departed Kiel on 13 April 1943. On the 22nd, she was attacked on two occasions by Catalina aircraft of No. 190 Squadron RAF. Both attacks caused no damage, although a man was lost overboard during the first. She was then attacked on the 23rd (twice), the first of which resulted in a flooded conning tower. She was also attacked on 21 May by American Avenger aircraft from the carrier USS Bogue. The result was a chlorine gas leak and both radio transmitters being knocked out.
The boat reached La Pallice in occupied France on 31 May.
This foray commenced from Bordeaux, took her to the middle of the Atlantic Ocean and terminated in La Pallice.
3rd patrol and loss
U-231 took part in eleven wolfpacks, namely.
- Star (27 April - 4 May 1943)
- Fink (4–6 May 1943)
- Elbe (7–10 May 1943)
- Elbe 1 (10–14 May 1943)
- Mosel (19–22 May 1943)
- Schlieffen (14–22 October 1943)
- Siegfried (22–27 October 1943)
- Siegfried 1 (27–30 October 1943)
- Körner (30 October - 2 November 1943)
- Borkum (1–3 January 1944)
- Borkum 3 (3–13 January 1944)
- Busch, Rainer; Röll, Hans-Joachim (1999). German U-boat commanders of World War II : a biographical dictionary. Translated by Brooks, Geoffrey. London, Annapolis, Md: Greenhill Books, Naval Institute Press. ISBN 1-55750-186-6.
- Busch, Rainer; Röll, Hans-Joachim (1999). Deutsche U-Boot-Verluste von September 1939 bis Mai 1945 [German U-boat losses from September 1939 to May 1945]. Der U-Boot-Krieg (in German). IV. Hamburg, Berlin, Bonn: Mittler. ISBN 3-8132-0514-2.
- Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.
- Kemp, Paul (1999). U-Boats Destroyed - German Submarine Losses in the World Wars. London: Arms & Armour. ISBN 1-85409-515-3.
- Helgason, Guðmundur. "The Type VIIC boat U-231". German U-boats of WWII - uboat.net. Retrieved 26 December 2014.
- Hofmann, Markus. "U 231". Deutsche U-Boote 1935-1945 - u-boot-archiv.de (in German). Retrieved 26 December 2014.