German submarine U-399 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.
She carried out one patrol. She sank one ship and caused another to be declared a total loss.
She was sunk in the English Channel on 26 March 1945.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-399 had a displacement of 769t when at the surface and 871t while submerged. She had a total length of 67.1m (220.1feet), a pressure hull length of 50.5m (165.7feet), a beam of 6.2m (20.3feet), a height of 9.6m (31.5feet), and a draught of 4.74m (15.55feet). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of NaNPS for use while surfaced, two Garbe, Lahmeyer & Co. RP 137/c double-acting electric motors producing a total of 750PS for use while submerged. She had two shafts and two 1.23abbr=onNaNabbr=on propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-399 was fitted with five 53.30NaN0 torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.82NaN2 SK C/35 naval gun, (220 rounds), one 3.7cm (01.5inches) Flak M42 and two twin 2sp=usNaNsp=us C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.
The submarine was laid down on 12 November 1942 at the Howaldtswerke (yard) at Kiel as yard number 31, launched on 4 December 1943 and commissioned on 22 January 1944 under the command of Oberleutnant zur See Kurt van Meteren.
She served with the 5th U-boat Flotilla from 22 January 1944 and the 11th flotilla from 1 February 1945.
The boat's first patrol was preceded by the short journey from Kiel in Germany to Horten Naval Base (south of Oslo), arriving at the Norwegian port on 28 January 1945.
U-399 departed Horten on 6 February 1945. On 21 March, she torpedoed the Liberty ship James Eagan Layne "about twelve miles off Plymouth". The ship was beached at nearby Whitesand Bay but settled on the bottom; at high water, only her masts and funnel showed. She was declared a total loss.
The boat sank the Dutch-registered Pacific on 26 March 1945. This ship had taken part in Operation Dynamo, the Dunkirk evacuation, in 1940.
U-399 was sunk later on the same day by depth charges from the British frigate .
Forty-six men died in U-399; there was one survivor.
| Date | Ship Name | Nationality | Tonnage (GRT) | Fate[1] | |
|---|---|---|---|---|---|
| 21 March 1945 | James Eagan Layne |  United States | 7,176 | Total loss | |
| 26 March 1945 | Pacific |  Netherlands | 362 | Sunk |