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British U-class submarine
HMS Ultimatum.jpg
The U class submarine HMS Ultimatum setting off from Holy Loch in August 1943
Class overview
Name: U
Preceded by: T class
Succeeded by: P611 class
Completed: 49
General characteristics
Type: Submarine
Displacement: 540 tons standard, 630 tons full load surfaced
730 tons submerged
Length: 191 ft (58 m)
Beam: 16 ft 1 in (4.90 m)
Draught: 15 ft 2 in (4.62 m)
Propulsion: 2 shaft diesel-electric
2 Paxman Ricardo diesel generators + electric motors
615 hp (460 kW), 825 hp (615 kW)
Speed: 11.25 knots (21 km/h) surfaced
10 knots (19 km/h) submerged
Range: 4,500 nmi (8,300 km) at 11 kn (20 km/h) surfaced
Complement: 27 to 31
Armament: 6 × 21 in (533 mm) torpedo tubes - 4 bow internal, 2 bow external (first group only)- 8 - 10 torpedoes
1 × 3 in (76 mm) gun

The British U class submarines (officially "War Emergency 1940 and 1941 programmes, short hull "[1]) were a class of 49 small submarines built just before and during the Second World War. The class is sometimes known as the Undine class, after the first submarine built.

Design and development

These small submarines, of around 630 tons, were originally intended as unarmed training vessels to replace the ageing H class, to be used as practice targets in anti-submarine training exercises.

The first three boats, HMS Undine, HMS Unity, and HMS Ursula were ordered in 1936, and during construction were modified to accommodate four internal and two external bow torpedo tubes. Apart from Undine and Unity, all boats were also equipped with a three-inch (76 mm) gun, although they lacked a hatch for the gun crew, who had instead to use the main conning tower hatch.

As war loomed, twelve more vessels were ordered, although only four had the external tubes (HMS Unique, HMS Upholder, HMS Upright and HMS Utmost). The external tubes were dropped from later vessels because they generated a large bow wave and made depth keeping more difficult at periscope depth.

They proved to be useful warships in the confined waters of the North Sea and particularly in the Mediterranean. A further 34 vessels, forming the third group, were ordered in 1940 and 1941. They were similar to the second group, but were lengthened by 5 feet (1.5 m) to provide a more streamlined shape. All but two of the 49 boats built were constructed by Vickers-Armstrong; the exceptions were HMS Umpire and HMS Una, both built at Chatham Dockyard. The submarines were powered by Paxman diesels generating 615 bhp (460 kW) and electric motors that could put out 825 shp (615 kW) giving a surface speed of 11.25 knots (21 km/h) and a submerged speed of 10 knots (19 km/h) .

Service history

Most of the boats built served with the 10th Submarine Flotilla based at Malta. 19 were lost during the war; 13 in the Mediterranean and the remainder in the North Sea and Atlantic Ocean. In addition, one vessel, HMS Untamed sank in May 1943 but was salvaged and reconstructed to be recommissioned as HMS Vitality. From 1941, some of the boats were transferred to Soviet, Free French and other allied navies. The design was developed into the welded V class later in the war.

Group one boats

The initial three 'U' class boats all entered service in the latter half of 1938. Initially designed as training vessels, they were effective enough to persuade the Admiralty to expand the class, and improve their offensive capabilities to pose a more effective threat to enemy shipping. Only Ursula would survive the war however. In addition, Ursula spent some time in service with an allied navy, in this case, the Soviet Navy, a practice that would be continued with other ships of the class.

Unity was the first British submarine to have a propeller designed for best submerged performance rather than surfaced performance.[2] It was thought this might reduce propeller noise.

Group two boats

The second group of the U-class consisted of twelve submarines, of a similar design to the original three, but most were modified to improve depth keeping. This group included a number of submarines that would go on to become particularly famous. Urchin was transferred to the Polish Navy, where, as the ORP Sokół, she sank a large amount of enemy shipping. One of the most famous U-class submarines was HMS Upholder, commanded for its entire career by Lieutenant-Commander Malcolm Wanklyn. Wanklyn received a Victoria Cross for attacking a well-defended convoy on 25 May 1941 and sinking an Italian liner, the Conte Rosso. In her 16 month operational career in the Mediterranean, before she was sunk in April 1942, Upholder carried out 24 patrols and sank around 119,000 tons of Axis ships – 3 U-boats, a destroyer, 15 transport ships with possibly a cruiser and another destroyer also sunk. Losses in this group were high, however. Only three out of the twelve survived the war.

Group three boats

These formed the largest group of 'U' class submarines, comprising 34 vessels ordered in three batches. Losses continued to be high. In June 1940 the decision was taken, in view of the anticipated high number of submarines to be ordered, to drop the practice of naming submarines, so these vessels were initially labelled P.31 to P.39, P.41 to P.49, etc., instead of receiving names. At the end of 1942 Churchill personally ordered that all submarines were to receive names, but eight ships were lost whilst in service with the Royal Navy, before they could have their names officially assigned. In addition, a number were assigned to allied navies, both before and after the war. One assigned to the Norwegian navy, HNoMS Uredd, was also lost after hitting a mine. The last surviving U-class boats were scrapped in the 1950s.

  • Note that four of the last batch received 'V' names rather than 'U' names; however, the last two were renamed upon transfer to the Free Norwegian and Free French Navies respectively, and the original names were re-assigned to new 'V' Class submarines.

Other navies

As well as serving with the Royal Navy, a number of U-class boats were transferred to operate with allied forces. The Soviet Navy received three boats:

  • V 2 - (ex HMS Unbroken)
  • V 3 - (ex HMS Unison)
  • V 4 - (ex HMS Ursula)

The Royal Norwegian Navy two:

The Polish Navy two:

The Free French Navy one:

The Royal Netherlands Navy one:

The Royal Danish Navy three:

  • S321 U 1 ''Springeren'' - (ex HMS P52)
  • S322 U 2 ''Støren'' - (ex HMS Vulpine)
  • S323 U 3 ''Sælen'' - (ex HMS Vortex)

In addition, both HMS Upstart and HMS Untiring were loaned to the Hellenic Navy after the end of the war, becoming Amphitriti and Xifias respectively.


  1. Conways All the worlds Fighting Ships 1922-46
  2. Brown DK Nelson to Vanguard p 112

External links

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