For the first Five Year Plan the Soviet Navy had designed submarines in various sizes for various missions. They had medium sized submarines of the D Class Dekabrist (Click for review of the Combrig D Class) and L Class Leninets (Click for review of the Combrig L Class), the small and numerous coastal submarines of the M Class Malyutka (Click for review of the Combrig M Class) to the large size of the P Class Pravda.
The P Class ,designed by the A.Asafov Design Team, was authorized in 1929. They were the first Soviet attempt to build a true ocean going submarine cruiser. Intended to operate with the Soviet surface fleet, they were given high surface speed and a heavy gun armament of two 100mm guns and one 45mm gun and a very large 1,200 ton (1,870 tons full load) displacement. The P Class proved to be a failure and only three were built, seeing limited action in World War Two.
While the members of the P Class were still building, under the second Five Year Plan, competition had begun between two design teams for the next class of Soviet submarine cruiser. One was under B. Malynin, who had designed the ill fated D Class and the other was the Submarine Department of the Soviet Navy Scientific and Research Institute of Armament and Shipbuilding, headed by Mikhail Alekseevich Rudnickii. The KE-9 (Kreyserskaya Eskadrennaya, Cruising Squadron) design of Rudnickii was the winner. The head designer was enthused with the KE-9 design that informally it was called the KR for Kreyser Rudnickogo (Rudnickii’s Cruiser).
The design benefited from a number of events. First the strengths and weaknesses of the D Class & L Class medium (originally called large) submarines was noticed, as members of those classes were operational. British submarine technology of the end of World War One was discovered when the British L55 was raised in the Baltic, studied and placed into Soviet service. The third and strongest influence came about when Soviet naval officers were allowed to closely inspect the Spanish E-1, later Turkish Gur. This boat, build to German plans, incorporated the latest German technology, which was the best in the world at that time. The Soviet S Class Stalinets was a medium sized design, which incorporated this technology and the very large size submarine cruiser of the K Class, as the KE-9 design, Series XIV, was classified, also benefited.
The members of the K Class were true deep ocean submarines with a size (1,490 tons/2,600 tons full load) that quite accurately could be called a submarine cruiser. The design was independent of the P Class and was a tremendous improvement over the earlier very large design in every category. With two 100mm guns, two 45mm guns, ten 21-inch torpedo tubes and two separate mine laying tubes, they packed a very heavy offensive punch in a design capable of close to 23 knots surfaced. From the start they were planned to be deployed with the northern fleet, rather than be used in the confined waters of the Baltic and Black Seas.
Crew habitability was given heavy emphasis, which is novel in itself in Soviet designs where crew comfort was considered a superfluous luxury. There was no hot bunking. Each enlisted man had their own berth that he did not have to share and each officer had their own small cabin. Designed to operate in the Arctic, the design had showers, two storerooms (one refrigerated) and an electric galley. Ventilation and air conditioning systems were much improved over earlier Soviet designs. All of these elements created a submarine far more capable of operating in the deep ocean than any other Soviet design. With these comparative comforts, the boats of the K Class were popular with their crews and affectionately given the nickname of Katyusha, the Russian form of Kate.
With launchings starting in 1938 the K Class came in two variants, easily differentiated by the shape of the bow. The first group of K-1, K-2, K-3, K-21, K-22, K-23 had a flat bow, while the second group K-51 through K-56 had a pronounced hump on the bow. The first group had been completed before the German invasion of June 1941 and were sent to the Northern Fleet. The second group was not ready and as they came on line had to stay in the Baltic as a water route to the Soviet Northern Fleet had been cut by enemy actions. The losses of this class all came from the first group, with all of them being sunk except for K-21. K-1 was lost October 1943 in the Kara Sea, presumably because of a mine. K-2 failed to return from a patrol off of Norway in August/September 1942. K-3 was sunk by German subchasers UJ1002, UJ1106 and UJ1111 off of Batsfjord on March 21, 1943. K-22 was mined off of Cape Harbaken on February 7, 1943 and K-23 was sunk by German subchasers UJ1101, UJ1109 and UJ1110 off of Olesa Fjord on May 12, 1942.
Probably the most dramatic moment in their service careers during the war came in the attack by K-21 on the German battleship Tirpitz. K-21 was part of a five submarine Soviet screening force for convoys PQ17 and QP13. In July 1942 Tirpitz, along with Admral Scheer, Prinz Eugen seven destroyers and two torpedo boats sailed to intercept PQ17, which due to this threat prematurely scattered and was subsequently massacred by German U-Boats and aircraft. K-21 sighted the German force and attacked the Tirpitz at the entrance of Altafjord on July 5, 1942. K-21 fired four torpedoes and then went deep to avoid counterattack from the numerous destroyers. The hydrophone operator thought he heard two explosions. After an hour K-21 went up and finding the sea vacant, surfaced to report a successful attack on the Tirpitz. Another Soviet source reported five explosions. However, the first that the German command knew of the attack was when they intercepted the report of K-21. No German ship had been hit. The sound that had been interpreted as explosions, probably was the sound created by tons of seawater hitting the rudder of Tirpitz as she changed courses in a zig-zag pattern.
As the most capable prewar Soviet submarine design, the K Class continued to serve in the Soviet Navy after the war. K-21 made the first Soviet submarine cruise off of the coats of the United States in October 1948. Some reports indicate that three of the class were given missile cylinders to test early versions of the Shaddock surface to surface cruise missile. Renumbered to K-55 in October 1949, K-21 was assigned as a stationary training ship in 1959 as UTS-5. She served in this capacity until 1980, when she was restored to her World War Two appearance. She opened as a museum on a concrete cradle at Severodvinsk on July 30, 1983. (History from Katyusha- Soviet Submarine Cruisers by Marek Twardowski Warship 1989; Submarines of World War Two by Erminio Bagnasco; and Conway’s All the World’s Fighting Ships 1922-1946.)
Combrig now has a 1:700 scale model of K-21, of the first, flat bowed group, of the K Class submarine. In keeping with the other models in the Combrig Soviet submarine series, the K-21 can be built as waterline or full hull, since hulls of both versions are included with the kit. However, with four deck guns and large streamlined conning tower, the K-21 is the largest of 1:700 World War Two submarine kits available from Combrig. Assembly is simple, especially the waterline version, and should please any submarine enthusiast. Since the K Class was the best Soviet design of World War Two or earlier, it is a fitting member in anyone’s 1:700 scale collection.