German submarine U-857

German submarine U-857 was a Type IXC/40 U-boat of Nazi Germany's Kriegsmarine built for service during the Second World War. She was ordered on 5 June 1941, laid down on 16 November 1942, and launched on 25 May 1943. For her operational lifespan, she was commanded by Kapitänleutnant Rudolf Premauer and had a crew complement of 59.

Design
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-857 had a displacement of 1144 t when at the surface and 1257 t while submerged. The U-boat had a total length of 76.76 m, a pressure hull length of 58.75 m, a beam of 6.86 m, a height of 9.60 m, and a draught of 4.67 m. The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4400 PS for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1000 shp for use while submerged. She had two shafts and two 1.92 m propellers. The boat was capable of operating at depths of up to 230 m.

The submarine had a maximum surface speed of 18.3 kn and a maximum submerged speed of 7.3 kn. When submerged, the boat could operate for 63 nmi at 4 kn; when surfaced, she could travel 13850 nmi at 10 kn. U-857 was fitted with six 53.3 cm torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.5 cm SK C/32 naval gun, 180 rounds, and a 3.7 cm Flak M42 as well as two twin 2 cm C/30 anti-aircraft guns. The boat had a complement of forty-eight.

Service history
She undertook three patrols, the first was for training. She sank two ships for a total tonnage of, and damaged one other ship on her last two patrols. She sank MV Belgian Airman on 14 April 1945, SS Swiftscout on 18 April 1945 and damaged MV Katy on 23 April 1945.

Fate
U-857 went missing since 30 April 1945 in the North Atlantic Ocean off the east coast of the United States. All hands were lost, and no wreckage was found.

The U-boat had been claimed to have been sunk by depth charge hedgehogs off the coast of Massachusetts on 7 April 1945 by USS Gustafson (DE-182) and was also thought to have been possibly sunk by USS Coffman (DE-191). However more recent commentary surmised that Gustafson had not hit her, and her loss is currently unexplained. U-857 was considered as a possible identity for the wreck that was ultimately determined to be U-869.