|Ordered:||29 November 1916|
|Builder:||Atlas e, Bremen|
|Launched:||17 April 1917|
|Commissioned:||22 August 1917|
|Fate:||Sunk in the Northern Barrage minefield on 25 September 1918. 77 dead.|
|General characteristics |
|Class and type:||German Type U 151 submarine|
|Height:||9.25 m (30 ft 4 in)|
|Draught:||5.30 m (17 ft 5 in)|
|Propulsion:||2 × shafts, 2 × 1.60 m (5 ft 3 in) propellers|
|Range:||25,000 nmi (46,000 km; 29,000 mi) at 5.5 knots (10.2 km/h; 6.3 mph) surfaced, 65 nmi (120 km; 75 mi) at 3 knots (5.6 km/h; 3.5 mph) submerged|
|Test depth:||50 metres (160 ft)|
|Complement:||6 officers, 50 enlisted|
SM U-156[Note 1] was a German Type U 151 U-boat commissioned in 1917 for the Imperial German Navy. From 1917 until her disappearance in September 1918 she was part of the U‑Kreuzer Flotilla, and was responsible for sinking 44 ships and damaging 3 others, including a warship. She took part in the Bombardment of Orleans.
U-156, built by the Atlas Werke in Bremen, was originally one of seven Deutschland class U-boats designed to carry cargo between the United States and Germany in 1916. Five of the submarine freighters were converted into long-range cruiser U-boats (U-kreuzers) equipped with two 15 cm deck guns, including U-156. They were the largest U-boats of World War I.
U-156 was launched on 17 April 1917 and commissioned on 22 August 1917 under Konrad Gansser, who commanded her until 31 December 1917, following which Richard Feldt took command of her on 1 January 1918.
On 15 June 1918, U-156 sailed with 77 crew. She passed through the North Sea, negotiated the Northern Passage around the northern end of the British Isles, and out into the Atlantic Ocean where she sailed for Long Island. She then proceeded to New York Harbor, where she had been ordered to lay mines. Records show that she was to lay a field of mines in the shipping lane along the south shore of Long Island, just east of the Fire Island lightship.
On 8 July 1918 U-156 stopped and scuttled the Norwegian owned Manx King at , which was traveling between New York and Rio de Janeiro. Captain Rasmus Emil Halvorsen and her crew were rescued from the lifeboats after 27 hours by DS Anchites of Liverpool, England.
U-156 had meanwhile headed north to attack the US fishing fleet. She sank 21 fishing boats in the Gulf of Maine area, from Cape Cod to the Bay of Fundy, ranging from the 72 ton schooner Nelson A. (4 August) to the 766 ton Dornfontein (2 August).
On 20 August, U-156 captured the Canadian trawler Triumph southwest of Canso, Nova Scotia. They manned and armed the vessel, and used it in conjunction with the submarine to capture and sink seven other fishing boats in the Grand Banks area, before eventually scuttling her.
On 25 September 1918, U-156 failed to report that she had cleared the Northern Passage around the United Kingdom on her return voyage to Germany and was presumed to have struck a mine of the Northern Barrage minefield.
Rene Bastin, a prisoner on SM U-140, claimed to have witnessed the fate of U-156. He said that he was on the bridge of U-140 while she was running the Northern Barrage in company with SM U-100, SM U-102, SM U-117 and U-156 when he suddenly saw U-156 blown up. He claimed that she was "blown 500 feet in the air". However, Bastin gave the date of this event as 22 October 1918, which was almost a month after the return to Germany of U-140, the submarine aboard which he was held captive. Additionally, U-140 never met up with U-156 and crossed the Northern Barrage with only U-117 for company on 17 September.
- "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot would be translated as His Majesty's Submarine.
- Gibson, R.H.; Maurice Prendergast (2002). The German Submarine War 1914-1918. Periscope Publishing Ltd. ISBN 1-904381-08-1.
- Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945 2. Translated by Thomas, Keith; Magowan, Rachel (London: Conway Maritime Press). ISBN 0-85177-593-4.
- Jung, Dieter (2004). Die Schiffe der Kaiserlichen Marine 1914-1918 und ihr Verbleib [German Imperial Navy ships 1914-1918 and their fate] (in German). Bonn: Bernard & Graefe. ISBN 3-7637-6247-7.
- Sheard, Bradley (1997). Lost Voyages: Two Centuries of Shipwrecks in the Approaches to New York. Aqua Quest Publications, Inc. ISBN 1-881652-17-3.
- Helgason, Guðmundur. "WWI U-boats: U 156". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net.