German submarine U-31 (1936)

For other ships with the same name, see German submarine U-31.

U-33, a typical Type VIIA boat
History
Nazi Germany
Name	U-31
Ordered	1 April 1935
Builder	AG Weser, Bremen
Cost	4,189,000 Reichsmark
Yard number	912
Laid down	1 March 1936
Launched	25 September 1936
Commissioned	28 December 1936
Recommissioned	30 July 1940
Decommissioned	24 March 1940
Fate	Sunk, 11 March 1940, raised sunk again 2 November 1940
General characteristics
Class and type	Type VIIA submarine
Displacement	626 t (616 long tons) surfaced 745 t (733 long tons) submerged
Length	64.51 m (211 ft 8 in) o/a 45.50 m (149 ft 3 in) pressure hull
Beam	5.85 m (19 ft 2 in) o/a 4.70 m (15 ft 5 in) pressure hull
Height	9.50 m (31 ft 2 in)
Draught	4.37 m (14 ft 4 in)
Installed power	2,100–2,310 PS (1,540–1,700 kW; 2,070–2,280 bhp) (diesels) 750 PS (550 kW; 740 shp) (electric)
Propulsion	2 shafts 2 × diesel engines 2 × electric motors
Speed	17 knots (31 km/h; 20 mph) surfaced 8 knots (15 km/h; 9.2 mph) submerged
Range	6,200 nmi (11,500 km; 7,100 mi) at 10 knots (19 km/h; 12 mph) surfaced 73–94 nmi (135–174 km; 84–108 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth	220 m (720 ft) Crush depth: 230–250 m (750–820 ft)
Complement	4 officers, 40–56 enlisted
Sensors and processing systems	Gruppenhorchgerät
Armament	5 × 53.3 cm (21 in) torpedo tubes (four bow, one stern) 11 × torpedoes or 22 TMA mines 1 × 8.8 cm (3.46 in) deck gun (220 rounds) 1 × 2 cm (0.79 in) AA gun
Service record
Part of:	2nd U-boat Flotilla 28 December 1936 – 12 March 1940 30 July – 2 November 1940
Identification codes:	M 28 961
Commanders:	Kptlt. Rolf Dau 28 December 1936 – 8 November 1938 Kptlt. Johannes Habekost 8 November 1938 – 11 March 1940 Kptlt. Wilfried Prellberg 30 July 1940 – 2 November 1940
Operations:	7 patrols: 1st patrol: 27 August – 2 September 1939 2nd patrol: 9 September – 2 October 1939 3rd patrol: 21 – 31 October 1939 4th patrol: 19 November – 11 December 1939 5th patrol: 15 January – 4 February 1940 6th patrol: 16 September – 8 October 1940 7th patrol: 19 October – 2 November 1940
Victories:	11 merchant ships sunk (27,751 GRT) 2 auxiliary warships sunk (160 GRT) 1 warship damaged (33,950 tons)

German submarine U-31 was a Type VIIA U-boat of Nazi Germany's Kriegsmarine during World War II. She was laid down on 1 March 1936 as yard number 912, launched on 25 September and commissioned on 28 December 1936.

Design

As one of the first ten German Type VII submarines later designated as Type VIIA submarines, U-31 had a displacement of 626 tonnes (616 long tons) when at the surface and 745 tonnes (733 long tons) while submerged. She had a total length of 64.51 m (211 ft 8 in), a pressure hull length of 45.50 m (149 ft 3 in), a beam of 5.85 m (19 ft 2 in), a height of 9.50 m (31 ft 2 in), and a draught of 4.37 m (14 ft 4 in). The submarine was powered by two MAN M 6 V 40/46 four-stroke, six-cylinder diesel engines producing a total of 2,100 to 2,310 metric horsepower (1,540 to 1,700 kW; 2,070 to 2,280 shp) for use while surfaced, two BBC GG UB 720/8 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 knots (31 km/h; 20 mph) and a maximum submerged speed of 8 knots (15 km/h; 9.2 mph). When submerged, the boat could operate for 73–94 nautical miles (135–174 km; 84–108 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 6,200 nautical miles (11,500 km; 7,100 mi) at 10 knots (19 km/h; 12 mph). U-31 was fitted with five 53.3 cm (21 in) torpedo tubes (four fitted at the bow and one at the stern), eleven 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.

Service history

During her career U-31 was involved in seven war patrols.

First patrol

U-31 was one of the few ocean-going submarines deployed to the Baltic Sea instead of the Atlantic Ocean on the eve of World War II. Departing Memel under the command of Johannes Habekost on 27 August, this uneventful trip was concluded quickly with the rapid destruction of the Polish Navy and the boat put in at Wilhelmshaven on 2 September.

Second patrol

After her quick return to Germany, U-31 became one of three Type VII reserve boats, going to sea again when Karl Dönitz ordered a redeployment of the U-boat force on 8 September. Ordered along with U-35 to save time by directly proceeding to the Atlantic via the English Channel, she attacked the first convoy of World War II, OB 4 on 16 September 1939, sinking the British steamer SS Aviemore. Habekost had found the convoy the day before and per orders reported the convoy's location, course and speed to Dönitz. Excited by this first reliable convoy report, he ordered all available boats to converge and attack the convoy. U-31 maneuvered into attack position and in the nighttime hours made an attack. Thinking he had sunk two ships, Habekost had however suffered torpedo failure, and thus only the 4,060 GRT Aviemore was actually sunk out of the convoy by U-31. U-31 would later sink the slightly larger Hazelside, of 4,646 GRT, on 24 September before concluding the patrol and returning to Wilhelmshaven on 2 October 1939.

First sinking

On 11 March 1940 U-31 was sunk in the Schillig Roads near buoy 12 (53°37′N 08°10′E) by four bombs from a Bristol Blenheim, O of No. 82 Squadron RAF, with the loss of 58 lives. The U-boat had been on trials and carried eleven workers from the shipyard and two assistants to the flotilla engineer in addition to her regular complement.

The U-boat was raised later that month, repaired and returned to service on 30 July 1940 with Kptlt. Prellberg in command.

Second sinking

U-31 was sunk again on 2 November 1940, north-west of Ireland, by depth charges from the British destroyer HMS Antelope, which picked up 44 survivors (or 43, sources vary), from the crew of 46.

In U-31's entire career she sank eleven merchant ships, totalling 27,751 gross register tons (GRT), and two auxiliary warships of 160 GRT. A mine laid by U-31 damaged the British battleship HMS Nelson of 33,950 tons.

Summary of raiding history

Date	Name of Ship	Nationality	Tonnage	Fate
16 September 1939	Aviemore	United Kingdom	4,060	Sunk
24 September 1939	Hazelside	United Kingdom	4,646	Sunk
1 December 1939	Arcturus	Norway	1,277	Sunk
3 December 1939	Ove Toft	Denmark	2,135	Sunk
4 December 1939	Gimle	Norway	1,271	Sunk
4 December 1939	HMS Nelson	Royal Navy	33,950	Damaged (mine)
4 December 1939	Primula	Norway	1,024	Sunk
6 December 1939	Agu	Estonia	1,575	Sunk
6 December 1939	Vinga	Sweden	1,974	Sunk
23 December 1939	HMS Glen Albyn	Royal Navy	82	Sunk (mine)
23 December 1939	HMS Promotive	Royal Navy	78	Sunk (mine)
22 September 1940	Union Jack	Faroe Islands	81	Sunk
27 September 1940	Vestvard	Norway	4,319	Sunk
29 October 1940	Matina	United Kingdom	5,389	Sunk

Bibliography

• 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). Der U-Boot-Krieg, 1939-1945: Deutsche U-Boot-Verluste von September 1939 bis Mai 1945 [German U-boat losses from September 1939 to May 1945] (in German). Vol. 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. Vol. 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.

External links

• Helgason, Guðmundur. "The Type VIIA boat U-31". German U-boats of WWII - uboat.net. Retrieved 8 December 2014.
• Hofmann, Markus. "U 31". Deutsche U-Boote 1935-1945 - u-boot-archiv.de (in German). Retrieved 7 December 2014.