|Ordered:||5 June 1941|
|Builder:||DeSchiMAG AG Weser, Bremen|
|Laid down:||31 October 1942|
|Launched:||11 May 1943|
|Commissioned:||19 August 1943|
|Fate:||scuttled in position Coordinates: on 7 April 1944 after receiving heavy damage from US warships|
|Class and type:||Type IXC/40 submarine|
|Height:||9.60 m (31 ft 6 in)|
|Draught:||4.67 m (15 ft 4 in)|
|Test depth:||230 m (750 ft)|
|Complement:||4 officers, 44 enlisted|
|Identification codes:||M 54 791|
|Commanders:||Oblt.z.S. Friedrich Wittenberg|
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-856 had a displacement of 1,144 tonnes (1,126 long tons) when at the surface and 1,257 tonnes (1,237 long tons) while submerged. The U-boat had a total length of 76.76 m (251 ft 10 in), a pressure hull length of 58.75 m (192 ft 9 in), a beam of 6.86 m (22 ft 6 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.67 m (15 ft 4 in). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged. She had two shafts and two 1.92 m (6 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 18.3 knots (33.9 km/h; 21.1 mph) and a maximum submerged speed of 7.3 knots (13.5 km/h; 8.4 mph). When submerged, the boat could operate for 63 nautical miles (117 km; 72 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 13,850 nautical miles (25,650 km; 15,940 mi) at 10 knots (19 km/h; 12 mph). U-856 was fitted with six 53.3 cm (21 in) torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.5 cm (4.13 in) SK C/32 naval gun, 180 rounds, and a 3.7 cm (1.5 in) SK C/30 as well as a 2 cm (0.79 in) C/30 anti-aircraft gun. The boat had a complement of forty-eight.
U-856 was ordered in June 1941 from DeSchiMAG AG Weser in Bremen under the yard number 1062. Her keel was laid down on 31 October 1942 and the U-boat was launched the following year on 11 May 1943. She was commissioned into service under the command of Oberleutnant zur See Friedrich Wittenberg (Crew X/37) in 4th U-boat Flotilla.
The U-boat was working up for deployment in the Baltic Sea until transferring to the 2nd U-boat Flotilla for front-line service. She left Kiel on 24 February 1944 for operations off the US east coast. In March she had two brief encounters with submarine-hunting aircraft, but escaped unscathed. In the morning of 7 April 1944 however, she was picked up by an aircraft of USS Croatan and attacked by USS Boyle. Surviving the initial attack, she was attacked with depth charges by a second group consisting of USS Huse and USS Champlin, the later ramming U-856 and severely damaging her. When the U-boat re-surfaced a little while later, she came under heavy artillery fire from the US warships. Wittenberg ordered the crew to abandon ship and scuttled her. Of the 55 men on board only 28, Wittenberg among them, survived. They were picked up by the destroyers and brought to New York City where they disembarked on 10 April 1944.