German submarine U-71 was a type VII C submarine of Nazi Germany's Kriegsmarine during the Second World War.
Ordered on 25 January 1939, her keel was laid down as yard number 618 on 21 December that year. She was launched on 31 October 1940 and commissioned on 14 December. She entered the 7th U-boat Flotilla as a training submarine (commissioning until 31 May 1941), then served as a front (operational) boat between 1 June 1941 and 31 May 1943. During that time she carried out ten war patrols, but had to return to port following damage after colliding with in the North Atlantic on 17 April 1943.
After that, she moved to the 24th U-boat Flotilla as a training submarine (1 June 1943 – 30 June 1944), then to the 22nd flotilla also as a training boat from 1 July 1944 until 27 February 1945. She was a member of 17 wolfpacks. She sank five ships and was scuttled on 2 May 1945 at Wilhelmshaven, six days before the German surrender.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-71 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 AEG GU 460/8–27 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-71 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, and one 2sp=usNaNsp=us C/30 anti-aircraft gun. The boat had a complement of between forty-four and sixty.
U-71s early history was fairly typical of many boats in the U-Boot-Waffe (U-boat arm); she began her operational life in Kiel, but soon moved to St. Nazaire in France, where despite being nearer to the main hunting grounds of the Atlantic, failed to take advantage of her more advanced location. This was between August 1941 and January 1942.
Her luck and that of her commander, Kapitänleutnant Walter Flachenberg, changed on her fifth foray, sinking a total of of shipping in March and April 1942. She returned to France, but this time to La Pallice.
Flachenberg was unable to repeat his success on U-71s sixth and his last patrol, returning to St. Nazaire empty-handed.
Under a new skipper, Hardo Rodler von Roithberg, the boat could not reproduce the form of her fifth patrol, despite sortieing three times between July 1942 and February 1943.
By now the writing was on the wall for Germany's U-boats; U-71 was only one submarine that departed La Rochelle and after another unsuccessful voyage, steamed to Königsberg (on the Baltic coast), arriving in May 1943.
U-71 took part in 17 wolfpacks, namely:
| - | Date | Ship | Nationality | Tonnage | Fate[1] |
|---|---|---|---|---|---|
| 17 March 1942 | Ranja |  Norway | 6,355 | Sunk | |
| 20 March 1942 | Oakmar |  United States | 5,766 | Sunk | |
| 26 March 1942 | Dixie Arrow | United States | 8,046 | Sunk | |
| 31 March 1942 | San Gerado |  United Kingdom | 12,915 | Sunk | |
| 1 April 1942 | Eastmoor | United Kingdom | 5,812 | Sunk |