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K-21
Class overview
Name	K class
Operators	Soviet Navy
Preceded by	Soviet S class
Succeeded by	Zulu class
In service	1939–1959
In commission	1940–1959
Planned	12
Completed	11
Cancelled	1
Lost	5
Retired	7
Preserved	1
General characteristics
Type	Submarine
Displacement	1,490 tons surfaced 2,600 tons submerged
Length	97.65 m (320 ft 4 in)
Beam	7.4 m (24 ft 3 in)
Draught	4.51 m (14 ft 10 in)
Propulsion	2-shaft diesel electric, 8,400 hp (6,300 kW) diesel, 2,400 hp (1,800 kW) electric
Speed	surface – up to 22.5 knots (41.7 km/h; 25.9 mph) submerged – 10 knots (19 km/h; 12 mph)
Range	14,000 nautical miles (26,000 km; 16,000 mi) at 11 knots (20 km/h; 13 mph)
Test depth	230 ft (70 m)
Complement	67 (10 officers)
Armament	6 × bow torpedo tubes 2 × stern torpedo tubes 2 × external stern torpedo tubes (24 torpedoes) 2 × 100 mm (4 in) guns 2 × 45 mm (1.8 in) guns 20 × mines

The K class or Kreiserskaya-class (Russian: Крейсерская, lit. 'cruiser') were a class of cruiser submarines and were the largest submarines built for the Soviet Navy during World War II. Eleven boats of the class were made, one was cancelled and scrapped. The K class submarines served in the Northern Fleet and the Baltic Fleet, and saw the most combat along the coast of Norway. They were also nicknamed the Katyusha-class.^[1]

The design was approved in 1936 as a long range "cruiser submarine" with a heavy torpedo and gun armament. The boats could operate as a fleet submarine working with the battle fleet or as long range commerce raiders. In January 1936, the project was originally designated as the KE-9 XIV Series (Russian: КЭ-9 XIV серии), short for "cruiser squadron" submarine (Russian: крейсерско-эскадренная).^[2]

They were a significantly improved version of the Pravda class and overcame most of their shortcomings (Conway's Fighting Ships). The double hull was divided into seven compartments. It was originally planned to carry a small floatplane for scouting but this concept was abandoned when the planned aircraft proved too flimsy.

Yakubov and Worth state that these were the most successful Soviet submarines of the World War II era, with high speed and good seakeeping. This class of submarine possessed better ventilation and air conditioning systems than any other class of Soviet submarine in World War II. They had amenities such as a bunk for every sailor, small cabins for each officer, showers, electric heaters (this class was designed to operate primarily in the Arctic), and an electric galley. The hull provided spacious accommodation. Diving time was 60 seconds. American naval constructors inspected K-21 in 1944, and thought the design to be workmanlike but technically inferior to contemporary American boats ^{[citation needed]} such as the Gato-class submarines

An improved design, the KU class, which was to be of welded construction was in planning in 1941. 24 KU boats were planned, but none were started.

All twelve boats were built by Marti Yard / Ordzhinikidze Yard, Leningrad, on the Baltic Sea, for the Soviet Northern Fleet. K-1 to K-23 were transferred before the German Invasion, and K-51 to K-56 were trapped in Leningrad during the blockade; they were completed after the war and transferred to the Arctic

• K-1

Laid down 27 December 1936

Launched 4 May 1938

Commissioned 26 May 1940

Missing in the Kara Sea after 5 September 1943

• K-2

Laid down 27 December 1936

Launched 4 May 1938

Commissioned 26 May 1940

Missing after 26 August 1942; likely sunk in September 1942 by mines near Tanafjord, Norway

• K-3

Laid down 27 December 1936

Launched 1938

Commissioned 19 December 1940

Sunk 21 March 1943 by German anti-submarine vessels near Båtsfjord, Norway

• K-21

Laid down 10 December 1937

Launched 16 August 1939

Commissioned 3 February 1941

Made an unsuccessful attack on the German battleship Tirpitz, during the PQ 17 convoy when she was commanded by Nikolai Lunin, stationary training ship 1959, saved as memorial

• K-22

Laid down 5 January 1938

Launched 3 November 1938,

Commissioned 7 August 1940

Sunk 7 February 1943 by mines

• K-23

Laid down 5 February 1938

Launched 28 April 1939

Commissioned 25 October 1940

Sunk 12 May 1942 by German anti-submarine vessels commanded by Wolfgang Kaden near Olesa Fjord, Norway, the boat was commanded by Magomet Gadzhiyev

• K-51

Laid down 26 February 1938

Launched 30 July 1939

Commissioned 17 September 1941

Stricken 13 March 1975

• K-52

Laid down 26 February 1938

Launched 5 December 1939

Commissioned 11 October 1942

Stricken 20 March 1978

• K-53

Laid down 30 May 1938

Launched 2 Sep 1939

Commissioned 31 Aug 1943

Stricken 11 March 1960

• K-54

Laid down 30 Apr 1937

Launched 8 Mar 1941

Never commissioned, scrapped in 1949

• K-55

Laid down 29 Apr 1937

Launched 7 Feb 1941

Commissioned 25 Dec 1944

Decommissioned 11 September 1954, stricken in 1964

• K-56

Laid down 17 Oct 1937

Launched 29 Dec 1940

Commissioned 25 Nov 1942

Decommissioned 30 December 1956, sunk 16 October 1957 during nuclear tests and stricken

• Gardiner, Robert & Chesneau, Roger, eds. (1980). Conway's All the World's Fighting Ships 1922–1946. London: Conway Maritime Press. ISBN 0-85177-146-7.
• Yakubov, Vladimir; Worth, Richard (2008). Raising the Red Banner: A Pictorial History of Stalin's Fleet 1920–1945. Chalford, Stroud: Spellmount. ISBN 978-1-86227-450-1.