Type U 31

Type U 31
Ship name	Type U 31 class
Caption	Imperial German Navy U-boat, Type U 31 series
Country	German Empire
Builder	Imperial German Navy
Laid down	1912–1914
Launched	1913–1915
Commissioned	1914–1915
Fate	varied: internment, scuttling, surrendered
Displacement	685–971 t surfaced/submerged
Length	64.7 m overall
Beam	6.32 m
Draught	3.56 m
Propulsion	diesel engines and electric motors
Speed	16.4 kn surfaced, 9.7 kn submerged
Range	8,790 nmi at 8 kn surfaced
Test depth	50 m (design)
Complement	4 officers, 31 enlisted
Armament	4 × 50 cm torpedo tubes, 1 × 8.8 cm SK L/30 deck gun

Type U 31

The Type U 31 was a class of U-boat built for the Imperial German Navy and deployed during World War I. Designed as large, ocean-going submarines, the class combined extended range for Atlantic operations with robust surface seakeeping for patrols around the British Isles, North Sea, and Atlantic Ocean. Members of the class served under commanders drawn from Kaiserliche Marine officer corps and participated in commerce raiding, fleet reconnaissance, and prize warfare alongside other U-boat types like the Type U 19 and Type U 63.

Design and specifications

The class featured a single-hull with double-bottom sections influenced by earlier designs such as U-31 (1908) predecessors and lessons from the Dreadnought era shipbuilding programs. Propulsion used twin MAN or M.A.N. two-stroke diesel engines and electric motors for submerged runs, giving a surfaced speed comparable to contemporary surface raiders like the SMS Emden and a submerged speed used in tactics refined after engagements with vessels such as the HMS Pathfinder and HMS Dreadnought. Endurance allowed patrols to reach waters around Azores, Madeira, and the approaches to the Mediterranean Sea, operating with ranges rivaling SM U-35 class boats. Habitability and internal arrangements reflected standards set by the Kaiserliche Werft Danzig and the tactical doctrines advocated by admirals including Henning von Holtzendorff.

Construction and shipyards

Construction occurred between 1912 and 1915 at major German yards including AG Vulcan Stettin, Friedrich Krupp Germaniawerft, Schiemag, and the Imperial Shipyard Wilhelmshaven. Contracts were awarded amid naval expansion debates involving figures such as Alfred von Tirpitz and parliamentary oversight in the Reichstag. Techniques borrowed from liners built by Blohm & Voss and destroyer construction at Kaiserliche Werft Kiel accelerated production to meet demands after outbreaks like the July Crisis and mobilization preceding Battle of the Falkland Islands operations. Subcontractors supplying diesel machinery and electrical systems included Sulzer and Siemens-Schuckertwerke.

Operational history

Boats of the class conducted patrols in contested waters during campaigns associated with milestones like the First Battle of the Atlantic and actions concurrent with the Gallipoli Campaign and the wider Naval warfare in World War I. They carried out commerce raiding that affected shipping tied to ports such as Liverpool, Le Havre, Marseille, and New York City indirectly through convoy interdiction. Engagements sometimes intersected with naval forces from Royal Navy, French Navy, United States Navy, and the Royal Canadian Navy. Commanders employed tactics developed from analyses of encounters like the Action of 31 May 1916 and responses to anti-submarine measures such as convoy escort doctrines advocated after losses like those suffered at RMS Lusitania and in actions around Orkney and Shetland approaches.

Command and crew

Crews typically numbered around 35 under commanding officers drawn from Kaiserliche Marine submarine schools including alumni of the U-Bootschule and staff trained at establishments in Kiel and Wilhelmshaven. Senior figures in submarine leadership such as Lothar von Arnauld de la Perière influenced training, discipline, and patrol directives that applied across classes including this one. Life aboard reflected routines noted in journals by submariners who later interacted with politicians like Friedrich von Ingenohl and naval strategists such as Erich Raeder. Crew composition included engineering specialists supplied by firms like Deutsche Werke and navigators familiar with charts from Admiralty-style publications.

Armament and sensors

Primary offensive armament comprised four 50 cm torpedo tubes—two bow and two stern—with torpedoes comparable to models used by boats like SM U-20 in early-war actions. A deck gun, typically the 8.8 cm SK L/30, provided surface engagement capability similar to armaments on contemporaries such as UB I and UC I classes. Sensors and situational awareness relied on periscopes produced by optical firms analogous to Zeiss and primitive hydrophones and listening gear developed in laboratories tied to research institutions like Kaiser Wilhelm Society. Fire-control methods evolved in response to countermeasures employed by escorts fielded by Admiralty and United States Navy forces.

Losses and fates

Outcomes for the class varied: some were sunk in actions against ships and patrols of the Royal Navy and French Navy during clashes near Heligoland Bight and the English Channel, others were interned in neutral ports such as Copenhagen and Rotterdam, and several were surrendered under the terms of the Armistice of 11 November 1918 and later scrapped at shipbreaking yards in Bremen and Morecambe Bay. Notable postwar dispositions paralleled those of surrendered boats allocated to navies including the Royal Navy for evaluation and the United States Navy for trials, with components studied by engineers from Vickers and firms such as Harland and Wolff.

Category:Submarine classes of the Imperial German Navy