German submarine U-978

German submarine U-978 was a World War II Type VIIC U-boat operated by Nazi Germany's Kriegsmarine. She completed the longest underwater patrol of World War II.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-978 had a displacement of 769 t when at the surface and 871 t while submerged. She had a total length of 67.10 m, a pressure hull length of 50.50 m, a beam of 6.20 m, a height of 9.60 m, and a draught of 4.74 m. The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2800 to 3200 PS for use while surfaced, two Brown, Boveri & Cie GG UB 720/8 double-acting electric motors producing a total of 750 PS for use while submerged. She had two shafts and two 1.23 m propellers. The boat was capable of operating at depths of up to 230 m.

The submarine had a maximum surface speed of 17.7 kn and a maximum submerged speed of 7.6 kn. When submerged, the boat could operate for 80 nmi at 4 kn; when surfaced, she could travel 8500 nmi at 10 kn. U-978 was fitted with five 53.3 cm torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm SK C/35 naval gun, 220 rounds, and one twin 2 cm C/30 anti-aircraft gun. The boat had a complement of between forty-four and sixty.

Service history
U-978 was commissioned on 12 May 1943 and assigned to 5th U-boat Flotilla for crew training. On 1 August 1944, U-978 was assigned to 3rd U-boat Flotilla for operational service, and completed one patrol with that unit. On 4 September 1944 she was ordered to 11th U-boat Flotilla, beginning service on 5 September. During her second war patrol, U-978 completed the longest underwater Schnorchel patrol of World War II, lasting 68 days, under command of Guenther Pulst. The record-breaking patrol began on 9 October 1944 when she left Bergen, Norway and ended on 16 December when she returned to Bergen from her patrol. This was two days longer than the famed underwater journey of GS U-977 to Argentina, shortly after Germany's surrender. During her two patrols U-978, did not sink any ships, but damaged one ship beyond repair, which measured.

Fate
U-978 survived the war as did her whole crew, and was surrendered at Trondheim on 9 May 1945. She was sunk on 11 December 1945 during Operation Deadlight by torpedoes at location 55.83333°N, -10.08333°W.