# SM UB-31

SM UB-31 was a German Type UB II submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. The U-boat was ordered on 22 July 1915 and launched on 16 November 1915. She was commissioned into the German Imperial Navy on 25 March 1916 as SM UB-31.
The submarine sank 27 ships in 25 patrols. UB-31 was depth charged and sunk by British warships HMS Lord Leitrim, HMS Loyal Friend, and HMS Ocean Roamer in the English Channel on 2 May 1918. Alternatively she may have been sunk by a mine on that date.

## Design

A Type UB II submarine, UB-31 had a displacement of 274 tonnes (270 long tons) when at the surface and 303 tonnes (298 long tons) while submerged. She had a total length of 36.90 m (121 ft 1 in), a beam of 4.37 m (14 ft 4 in), and a draught of 3.69 m (12 ft 1 in). The submarine was powered by two Benz six-cylinder diesel engines producing a total 270 metric horsepower (270 shp; 200 kW), two Siemens-Schuckert electric motors producing 280 metric horsepower (210 kW; 280 shp), and one propeller shaft. She was capable of operating at depths of up to 50 metres (160 ft).
The submarine had a maximum surface speed of 9.06 knots (16.78 km/h; 10.43 mph) and a maximum submerged speed of 5.71 knots (10.57 km/h; 6.57 mph). When submerged, she could operate for 45 nautical miles (83 km; 52 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 7,030 nautical miles (13,020 km; 8,090 mi) at 5 knots (9.3 km/h; 5.8 mph). UB-31 was fitted with two 50 centimetres (20 in) torpedo tubes, four torpedoes, and one 8.8 cm (3.5 in) Uk L/30 deck gun. She had a complement of twenty-one crew members and two officers and a 42-second dive time.

## Summary of raiding history

| Date | Name | Nationality | Tonnage | Fate |
| 9 April 1917 | Kittiwake | United Kingdom | 1,866 | Sunk |
| 24 April 1917 | Saint Jacques | France | 415 | Damaged |
| 28 April 1917 | Medina | United Kingdom | 12,350 | Sunk |
| 21 May 1917 | City of Corinth | United Kingdom | 5,870 | Sunk |
| 15 June 1917 | Teesdale | United Kingdom | 2,470 | Damaged |
| 17 June 1917 | Stanhope | United Kingdom | 2,854 | Sunk |
| 5 July 1917 | Ocean Swell | United Kingdom | 195 | Sunk |
| 6 July 1917 | Ariadne Christine | United Kingdom | 3,550 | Damaged |
| 7 July 1917 | Bellucia | United Kingdom | 4,368 | Sunk |
| 10 July 1917 | Hildegard | United States | 622 | Sunk |
| 11 July 1917 | Brunhilda | United Kingdom | 2,296 | Sunk |
| 1 August 1917 | Alcyone | United Kingdom | 149 | Sunk |
| 1 August 1917 | Laertes | United Kingdom | 4,541 | Sunk |
| 2 August 1917 | Newlyn | United Kingdom | 4,019 | Sunk |
| 3 August 1917 | Renee Marthe | France | 49 | Sunk |
| 8 August 1917 | Algerie | France | 3,386 | Damaged |
| 8 September 1917 | Elizabeth | United Kingdom | 58 | Sunk |
| 9 September 1917 | Pluton | Norway | 1,449 | Sunk |
| 19 October 1917 | Waikawa | United Kingdom | 5,666 | Sunk |
| 20 October 1917 | Colorado | United Kingdom | 7,165 | Sunk |
| 23 October 1917 | Lepanto | United Kingdom | 6,389 | Damaged |
| 19 November 1917 | Farn | United Kingdom | 4,393 | Sunk |
| 13 December 1917 | Britannic | United Kingdom | 92 | Sunk |
| 15 December 1917 | Sachem | United Kingdom | 5,354 | Damaged |
| 18 December 1917 | Riversdale | United Kingdom | 2,805 | Sunk |
| 20 December 1917 | Alice Marie | United Kingdom | 2,210 | Sunk |
| 20 December 1917 | Eveline | United Kingdom | 2,605 | Sunk |
| 20 December 1917 | Warsaw | United Kingdom | 608 | Sunk |
| 22 January 1918 | Admiral Cochrane | United Kingdom | 6,565 | Damaged |
| 22 January 1918 | Greatham | United Kingdom | 2,338 | Sunk |
| 24 January 1918 | Elsa | Norway | 3,581 | Sunk |
| 28 February 1918 | Heenvliet | Netherlands | 492 | Sunk |
| 20 March 1918 | Boorara | Australia | 6,570 | Damaged |
| 24 April 1918 | Agnete | United Kingdom | 1,127 | Sunk |
| 25 April 1918 | Joseph | France | 42 | Sunk |