German submarine U-870 was a Type IXC/40 U-boat of Nazi Germany's Kriegsmarine built for service during the Second World War. She was ordered on 25 August 1941, and laid down on 29 April 1943 at Bremen, Germany. She was launched on 29 October 1943 and commissioned on 3 February 1944.
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-870 had a displacement of 1144t when at the surface and 1257t while submerged. The U-boat had a total length of 76.76m (251.84feet), a pressure hull length of 58.75m (192.75feet), a beam of 6.86m (22.51feet), a height of 9.6m (31.5feet), and a draught of 4.67m (15.32feet). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4400PS for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1000shp for use while submerged. She had two shafts and two 1.92abbr=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-870 was fitted with six 53.30NaN0 torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.52NaN2 SK C/32 naval gun, 180 rounds, and a 3.7cm (01.5inches) Flak M42 as well as two twin 2sp=usNaNsp=us C/30 anti-aircraft guns. The boat had a complement of forty-eight.
For her one patrol, she had one commander, Korvettenkapitän Ernst Hechler, who was awarded the Knight's Cross of the Iron Cross. Over her career she claimed two warships sunk, total of 1,960 tons, one warship damaged for a total of 1,400 tons, and two ships a total loss, total of .On 20 December 1944, U-870 attacked a small group of landing ships, damaging and sinking the 1,625-tons vessel . The U-boat was then attacked by a British aircraft from No. 220 Squadron RAF but got away, also evading two hunter-killer groups of vessels.
She was sunk on 30 March 1945 at Bremen by US bombs.
| Date | Ship Name | Nationality | Tonnage[1] | Fate[2] |
|---|---|---|---|---|
| 20 December 1944 | 1,400 | Damaged at 43.0333°N -38°W | ||
| 20 December 1944 | 1,625 | Sunk at 42.0667°N -27°W | ||
| 3 January 1945 | Henry Miller |  United States | 7,207 | Total loss at 35.85°N -30°W |
| 9 January 1945 | FFL L´Enjoue | 335 | Sunk at 35.9333°N -54°W | |
| 10 January 1945 | Blackheath |  United Kingdom | 4,637 | Total loss at 35.8167°N -9°W |