SM U-18 (second row, second from the right)
History
Germany
Name	U-18
Ordered	May 6, 1910
Builder	Kaiserliche Werft Danzig
Cost	2,333,000 Goldmark
Yard number	12
Laid down	27 October 1910
Launched	25 April 1912
Commissioned	17 November 1912
Fate	Scuttled - 23 November 1914 1 dead
General characteristics
Class and type	German Type U 17 submarine
Displacement	564 t (555 long tons) surfaced 691 t (680 long tons) submerged
Length	62.35 m (204 ft 7 in)
Beam	6 m (19 ft 8 in)
Height	7.30 m (23 ft 11 in)
Draught	3.40 m (11 ft 2 in)
Propulsion	2 shafts 2 × 2 Körting 8-cylinder two stroke paraffin motors with 1,400 PS (1,030 kW; 1,380 shp) 2 × AEG electric motors with 1,120 PS (820 kW; 1,100 shp) 550 rpm surfaced 425 rpm submerged
Speed	14.9 knots (27.6 km/h; 17.1 mph) surfaced 9.5 knots (17.6 km/h; 10.9 mph) submerged
Range	6,700 nmi (12,400 km; 7,700 mi) at 8 kn surfaced 75 nmi (139 km; 86 mi) at 5 kn submerged
Test depth	50 m (164 ft 1 in)
Boats & landing craft carried	1 dingi
Complement	4 officers, 25 men
Armament	4 × 45 cm (17.7 in) torpedo tubes (2 each bow and stern) with 6 torpedoes
Service record
Part of:	II Flotilla 1 August – 23 November 1914
Commanders:	Kptlt. Heinrich von Henning[1] 1 August – 23 November 1914
Operations:	3 patrols
Victories:	None

SM U-18^{[Note 1]} was one of 329 submarines serving in the Imperial German Navy in World War I. U-18 engaged in the commerce warfare in the First Battle of the Atlantic.

Beginning in October 1914, she was commanded by Kaptlt. von Hennig.^[2]

On her third mission, on 23 November U-18 penetrated the fleet anchorage of Scapa Flow via Hoxa Sound, following a steamer through the boom and entering the anchorage with little difficulty. However, the fleet was absent, being dispersed in anchorages on the west coast of Scotland and Ireland. As U-18 was making her way back out through Hoxa Sound to the open sea, her periscope was spotted by a guard boat. The trawler Dorothy Gray altered course and rammed the periscope, rendering it unserviceable. U-18 then suffered a failure of her diving plane motor and the boat became unable to maintain her depth, at one point even impacting the seabed. She was rammed a second time by destroyer HMS Garry and eventually, her captain was forced to surface and scuttle his command just outside the Hoxa Gate; all crew members, except one, were picked up by British boats.^[3][4] One crew member perished, while the remaining 22 were interned as prisoners of war.^[5]

The wreck lies 75 m (246 ft) below the surface just outside the Hoxa Gate, at 58°41′N 02°55′W / 58.683°N 2.917°W / 58.683; -2.917.^[6]

• Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. Vol. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.
• Spindler, Arno (1966) [1932]. Der Handelskrieg mit U-Booten. 5 Vols. Berlin: Mittler & Sohn. Vols. 4+5, dealing with 1917+18, are very hard to find: Guildhall Library, London, has them all, also Vol. 1-3 in an English translation: The submarine war against commerce.
• Beesly, Patrick (1982). Room 40: British Naval Intelligence 1914-1918. London: H Hamilton. ISBN 978-0241108642.
• Halpern, Paul G. (1918). A Naval History of World War I. New York: Routledge. ISBN 978-1857284980.
• Roessler, Eberhard (1997). Die Unterseeboote der Kaiserlichen Marine. Bonn: Bernard & Graefe. ISBN 978-3763759637.
• Schroeder, Joachim (2002). Die U-Boote des Kaisers. Bonn: Bernard & Graefe. ISBN 978-3763762354.
• Koerver, Hans Joachim (2008). Room 40: German Naval Warfare 1914-1918. Vol I., The Fleet in Action. Steinbach: LIS Reinisch. ISBN 978-3-902433-76-3.
• Koerver, Hans Joachim (2009). Room 40: German Naval Warfare 1914-1918. Vol II., The Fleet in Being. Steinbach: LIS Reinisch. ISBN 978-3-902433-77-0.
• Kemp, Paul (1997). U-boats destroyed, German submarine losses in the World Wars. London: Arms & Armour Press. p. 9. ISBN 1-85409-321-5.

• Helgason, Guðmundur. "WWI U-boats: U 18". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net.
• Room 40: Archived 2018-10-15 at the Wayback Machine original documents, photos and maps about World War I German submarine warfare and British Room 40 Intelligence from The National Archives, Kew, Richmond, UK.