German submarine U-657

German submarine U-657 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 5 October 1940 by Howaldtswerke, Hamburg as yard number 806, launched on 12 August 1941 and commissioned on 8 October 1941 under Oberleutnant zur See Hans-Jürgen Radke.

Radke was killed in a fire while the boat was undergoing trials on 14 December 1941.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-657 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 Siemens-Schuckert GU 343/38–8 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-657 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 a 2 cm C/30 anti-aircraft gun. The boat had a complement of between forty-four and sixty.

Service history
The boat's career began with training at 8th U-boat Flotilla on 8 October 1941, followed by active service on 1 March 1942 as part of the 3rd Flotilla in La Pallice, France. Four months later, she transferred to 11th Flotilla, in Bergen, Norway, for the remainder of her service.

In seven patrols she sank one merchant ship, for a total of.

Wolfpacks
U-657 took part in six wolfpacks, namely:
 * Naseweis (31 March – 10 April 1942)
 * Eisteufel (21 June – 8 July 1942)
 * Nebelkönig (27 July – 14 August 1942)
 * Nordwind (24 January – 4 February 1943)
 * Iller (12 – 15 May 1943)
 * Donau 1 (15 – 17 May 1943)

Fate
U-657 was sunk on 17 May 1943 in the North Atlantic, E of Cape Farewell, Greenland, in position 58.9°N, -42.55°W, by depth charges from Royal Navy frigate HMS Swale (K217). All hands were lost.