German submarine U-400

German submarine U-400 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.

The submarine was laid down on 18 November 1942 at the Howaldtswerke yard in Kiel as yard number 32, launched on 8 January 1944 and commissioned on 18 March under the command of Kapitänleutnant Horst Creutz.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-400 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 Garbe, Lahmeyer & Co. RP 137/c 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-400 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), one 3.7 cm Flak M42 and two twin 2 cm C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.

Service history
After training with the 5th U-boat Flotilla, U-400 was attached to the 11th U-boat Flotilla for front-line service on 1 November 1944.

The U-boat sailed from Horten Naval Base in Norway for her first war patrol on 15 November 1944, and headed for the waters off Land's End. Despite repeated requests for reports by the German U-boat Command, none were received. The U-boat was eventually listed as "missing" at the end of January 1945. After the war, the Allies attributed the loss of U-400 to a depth charge attack by the frigate HMS Nyasaland (K587) on 17 December 1944, about 30 nmi SE of Kinsale, Ireland.

Discovery
The wreck of U-400 was finally identified by nautical archaeologist Innes McCartney and historian Axel Niestle in 2006, about 10 mi north-west of Padstow, Cornwall, at position 50.665°N, -5.08333°W close to the wrecks of two other U-boats, GS U-325 and GS U-1021. All three submarines were sunk in the Bristol Channel by a deep-trap minefield.

The U-boat sunk by Nyasaland is now believed to have been GS U-772.

Previously recorded fate
U-400 was noted as sunk in mid-December 1944 in the British minefield 'HX A1' off the Cornish coast.