History
Nazi Germany
Name	U-713
Ordered	7 December 1940
Builder	H. C. Stülcken Sohn, Hamburg
Yard number	779
Laid down	21 October 1941
Launched	24 September 1942
Commissioned	29 December 1942
Fate	Missing in the Norwegian Sea northwest of Narvik since 24 February 1944. No explanation for her loss.
General characteristics
Class and type	Type VIIC submarine
Displacement	769 t (757 long tons) surfaced 871 t (857 long tons) submerged
Length	67.10 m (220 ft 2 in) (o/a) 50.50 m (165 ft 8 in) (pressure hull)
Beam	6.20 m (20 ft 4 in) (o/a) 4.70 m (15 ft 5 in) (pressure hull)
Height	9.60 m (31 ft 6 in)
Draught	4.74 m (15 ft 7 in)
Installed power	2,800–3,200 PS (2,100–2,400 kW; 2,800–3,200 bhp) (diesels) 750 PS (550 kW; 740 shp) (electric)
Propulsion	2 shafts 2 × diesel engines 2 × electric motors
Speed	17.7 knots (32.8 km/h; 20.4 mph) surfaced 7.6 knots (14.1 km/h; 8.7 mph) submerged
Range	8,500 nmi (15,700 km; 9,800 mi) at 10 knots (19 km/h; 12 mph) surfaced 80 nmi (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth	230 m (750 ft) Crush depth: 250–295 m (820–968 ft)
Complement	4 officers, 40–56 enlisted
Armament	5 × torpedo tubes (four bow, one stern) 14 × 53.3 cm (21 in) torpedoes or 26 TMA mines 1 × 8.8 cm (3.46 in) deck gun (220 rounds) 2 × twin 2 cm (0.79 in) C/30 anti-aircraft guns
Service record
Part of:	8th U-boat Flotilla 29 December 1942 – 30 June 1943 11th U-boat Flotilla 1 July – 31 October 1943 13th U-boat Flotilla 1 November 1943 – 24 February 1944
Identification codes:	M 49 449
Commanders:	Oblt.z.S. Henri Gosejacob 29 December 1942 – 24 February 1944
Operations:	4 patrols: 1st patrol: 3 July – 20 August 1943 2nd patrol: 8 September – 27 October 1943 3rd patrol: a. 22 November – 9 December 1943 b. 12 – 14 December 1943 c. 3 – 5 February 1944 4th patrol: 5 – 24 February 1944
Victories:	None

German submarine U-713 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 21 October 1941 at the H. C. Stülcken Sohn yard at Hamburg, launched on 24 September 1942, and commissioned on 29 December 1942 under the command of Oberleutnant zur See Henri Gosejacob.

Attached to 8th U-boat Flotilla based at Danzig, U-713 completed her training period on 30 June 1943 and was assigned to front-line service.

German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-713 had a displacement of 769 tonnes (757 long tons) when at the surface and 871 tonnes (857 long tons) while submerged.^[1] 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 Garbe, Lahmeyer & Co. RP 137/c 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).^[1]

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).^[1] 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-713 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 two twin 2 cm (0.79 in) C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.^[1]

U-713 was missing since 24 February 1944 in the Norwegian Sea north-west of Narvik.^[2]

While operating against convoy JW 57 on 24 February 1944, U-713 was spotted by a Swordfish from HMS Chaser. The destroyer HMS Keppel was directed towards the U-boat and attacked with depth charges, sinking U-713 in position 69°27′N 4°53′E / 69.450°N 4.883°E / 69.450; 4.883.^[3]

• Helgason, Guðmundur. "The Type VIIC boat U-713". German U-boats of WWII - uboat.net. Retrieved 23 July 2015.