Königsberg-class (K-class) light cruisers

A brief overview of the German Königsberg-class light cruisers, also known as K-class cruisers

After World War One, and in accordance with the Treaty of Versailles, the navy of Germany was left with only eight cruisers, two of them kept in reserve (These cruisers were Niobe, Nymphe, Thetis, Amazone, Medusa, Arcona, Hamburg and Berlin). All of them were pre-WW1 designs, had a displacement of around 3,000t, a top speed of 23kn and were armed with 105mm guns. All of them were outdated and were not very seaworthy due to their age.

The first replacement cruiser, Emden (which had replaced Niobe), although armed with 150mm guns, still had a gun arrangement like these old cruisers, with single guns arranged all around the ship in relatively unprotected mountings. The French Dugay-Trouin-class from the early 20s, armed with four twin 155mm turrets and a top speed of 33kn, showed the way how ‘modern’ fleet cruisers should look. In 1924 the first design work began on a successor class for Emden.

Using a new definition for standard displacement introduced by the Washington Fleet Treaty, the designers were able to design a much heavier ship than Emden (~+750t). Original thoughts included a design with four twin 150mm turrets, like its French counterpart, and a design with four 190mm twin turrets. The latter was dropped because it would have surely caused a veto from the Treaty nations and because a gun with this caliber did not exist and would have to be developed. The former design was dropped in favor for three triple 150mm turrets, which meant less weight combined with more firepower.

The orders for construction were given 1925 for the first cruiser, the next two followed in 1926. Two orders were given to Reichsmarinewerft Wilhelmshaven, one to Deutsche Werke Kiel. In the budget, the cruisers were planned as follows:
-Kreuzer ‘B’ (Ersatz Thetis): Königsberg
-Kreuzer ‘C’ (Ersatz Medusa): Karlsruhe
-Kreuzer ‘D’ (Ersatz Arcona): Köln

The names were chosen for WW1 cruisers that had been sunk fighting superior enemy forces. As all names started with the letter ‘K’, the class earned the name ‘K’-class. The final design, as shown below, had a length 174m, a beam of 15.2m, a Standard Displacement of 6,000ts and was armed with nine 150mm guns L/60 C/25 mounted in triple turrets C/25. Anti-air consisted of the newly-developed 88mm Flak L/75 C/25 in twin mount C/25 between the funnels and the aft guns with and additionally four light twin Flak cannons on platforms around the aft superstructure. The cruiser also had four triple 500mm torpedo tubes and carried 24 torpedoes (12 in tubes and 12 in storage) and, if necessary, could also carry up to 120 mines.
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What was unique for these cruisers was the asymmetrical arrangement of the two aft guns. The Königsberg-class had been planned to fill the role of a commerce raider as well as that of a fleet and scout cruiser. Serving as a scout cruiser, the Königsberg-class would have to come relatively close to enemy forces, as airplanes were forbidden by the Treaty of Versailles and radar had not been developed yet. To keep pursuers at bay – and for the role as commerce raider – two turrets were placed aft. However, to gain additional firepower in forward direction, the aft turrets were placed asymmetrical, off the centerline. Tower ‘B’ was placed 2.25m to port from the centerline, Tower ‘C’ 1.95 to starboard. This allowed for greater turning circles and – with a high barrel angle and the mast folded down – the turrets could fire directly ahead, if necessary.

The cruisers had two shafts and a top speed 32kn and were driven by four steam turbines fired by six oil boilers. For slower speeds (~10kn) they also had 2 auxiliary 10-zylinder diesel engines. To accommodate with the maximum displacement of 6,000ts of the Treaty of Versailles, an extensive amount of electric welding was used during the construction, material thickness was made as thin as possible, and installation elements were included for structural stability.

Compared to their counterparts of the French Dugay-Trouin-class, the Königsberg-class had better armor, superior targeting and firepower. However, due to the massive amount of electric welding, the Königsberg-class had weaker overall structural integrity and very instable seagoing qualities. Even slightly rough weather would have neglected the advantages of targeting and not allowed for a clear shot on the enemy.

The first cruiser, Königsberg, named for the city and SMS Königsberg of 1905, was launched on March 26th in 1927 and commissioned on April 17th, 1929. The new twin 88mm weren’t ready yet, and instead two WW1-era 88mm single Flaks SKL/45 in center mount MPL/13 were installed. The light twin Flaks were left out altogether, but the platforms remained.
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The second cruiser, Karlsruhe, named for the city and SMS Karlsruhe of 1912, was launched on November 20th, 1927 and commissioned on November 6th, 1929. Like Königsberg, she was equipped with older, single Flaks, but she had a two-storied forwards mast, which made her unique among her sisters.
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The third cruiser, Köln, named for the city and SMS Cöln of 1909, was launched on May 23rd, 1928 and commissioned on January 15th, 1930. Köln was equipped with the new 88mm twin Flaks, as well as a control station, which directed each Flak with eight different remote controls. However, the whole design was not satisfactory: The Flak-barrels, arranged on the sides and not the center, caused instabilities and the turning speed of 10°/sec was deemed unsatisfactory. Until the development of a new 88mm twin Flak in the late thirties, the old 88mm SKL/45 stayed in service.
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The cruisers spent their years as training cruisers. Their travels visiting harbors into foreign waters showed new generations of naval personnel the world and also represented a new, open-minded, democratic Germany to other nations.
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By 1934, the threat of aircraft had become larger and the AA armament was increased. On each side of the aft superstructure, a new 88mm single Flak was installed. The forward section sported eight 37mm L/83 C/30 Flaks in twin mounts C/30. Also, plans were made for the installation of aircraft facilities, as shown with installment of a larger crane on port.
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In the mid-to-late thirties all cruisers had received numerous upgrades: The torpedo tube caliber had been increased to 533mm for the new G7a torpedoes. The aft superstructure had been rebuilt to house a stabilized control station (Stabilisierter Leitstand, SL-1) with 3m-Rangefinder for the new 88mm Flak L/76 C/32 in twin mount C/32. Each ship carried three of them. Light AA was increased with four 20mm FlaMG L/65 C/30 in single mount C/30 for Köln and [/i]Karlsruhe[/i]

Airplane installation had been planned for these ships from the beginning, although they had been forbidden at that time (the government had hoped for a lift of restriction). During the mid-thirties, an FL-22 aircraft catapult was installed midships, two Heinkel He-60 floatplanes could be supported (One on the catapult, one disassembled below deck, although in practice, only one was usually onboard)
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Köln, as opposed to her sisters, carried a more massive aircraft crane, similar to one later seen on Leipzig.
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With the outbreak of the Spanish Civil War in 1936 Germany sent several ships to Spain, which included several cruisers of the Königsberg-class. All ships carried neutrality markings consisting of black-white-red stripes, denoting their nationality.
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Königsberg also was chosen as a testbed for radar equipment in 1937: A house on the forward superstructure carried a number of different radar prototypes on the front side. From 1936-1938 she served under the navy inspection, during which two heavy Flaks were removed.
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While the K-class had been a balanced design at launch, the additional weight of added armament and equipment, combined with the weak structural integrity, caused serious strain on the class’s body. This became obvious in 1936, when Karlsruhe was damaged in a storm off the coast of San Diego and had to be repaired in a US naval yard. It also showed during the Spanish Civil War: The cruisers had to cross the stormy Bay of Biscay, which caused further damage. To counter this, several actions were taken: Orders were given to empty the middle fuel tank last and always keep a minimum 680t of fuel in the tanks. Köln underwent a maintenance which reinforced her internal structure. However, to keep stability, the gained weight had to be shed in other places, namely with the removal of the aircraft catapult, the crane and other equipment (A different grate crane was reinstalled a short time later for better boat handling). This allowed Köln the return to Spanish waters, but only in favorable weather.
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It became obvious that the K-cruisers in their current form had some serious flaws. To encounter these problems and prolong the lifespan of the ships, a massive refit program was started. This included:
-Removal of the auxiliary diesels. These machines had proven to be too complicated and took up too much space.
-Capped funnels
-Installation of a tripod mast behind the aft funnel
-Rearrangement of the searchlight to platforms on the side of the funnels
-Replacement of the 88mm twin Flak with 105mm Flak SKC/33 in twin mount C/31
-Replacement of the old cranes with modern level luffing cranes
-Installation of a retracting bow protection device, 105mm exercise cannon and degaussing cable
-Replacement of the He-60 with an Ar-196

These refits were planned in the order Karlsruhe, Köln, Königsberg, beginning in 1398, 1939 and 1940, respectively and lasting for around nine months. All ships would have been used as torpedo- and artillery-training and –testing. Because of the massive fleet expansion program and the outbreak of the war, only Karlruhe underwent the refit.
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All three cruisers participated in the Invasion of Norway. Köln and Königsberg were part of Warship Group Three with the target of Bergen. For the invasion, Königsberg was fitted with a degaussing cable and received a new Ar-196 floatplane. During the battle on April 9th, Königsberg was damaged by Norwegian coastal batteries and had to remain behind for repairs. On April 10th, British Skua divebombers attacked the ship. Königsberg capsized and sank in the harbor.
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That, however was not the complete end of her ‘career’. In the same year, plans were made to repair the ship underwater and raise it. This finally succeeded in 1942, and the wreck was used as a U-boat pier, until she sunk again in 1944. Additionally tries at raising her failed and she was beached in a nearby bay in 1945. She was towed to Stavanger in 1947 and broken up.

Karlsruhe was part of Warship Group Four with the target of Kristiansand and Arendal. She survived the battle, but on the way back to Germany, she was torpedoed by the British submarine HMS Truant, which resulted in eleven dead and the loss of all machines and generators. With Karlsruhe heavy listing, the Captain decided to give up the ship. The crew was taken over by torpedo boats Luchs and Seeadler, while torpedo boat Greif sunk the cruiser with two additional torpedoes. The waves closed over Karlsruhe at 10:50pm on April 9th, 1940.

Köln successfully returned home to Germany and was used for commerce raiding and minelaying operations. During the summer of 1940, a degaussing cable was installed; the aft torpedo tubes and lower searchlights on the cranes were removed. The K-class carried a heavy torpedo armament, but that had proven useless during the war. In 1941, now with a new camouflage paintjob, the lower searchlight platforms and the larger crane had been removed as well. During this time, Köln served as a testbed for the new helicopters. On top of turret ‘B’ (Bruno), a wooden platform was installed that allowed the landing and take-off of either a Flettner Fl-265 or Fl-282.
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By 1944, Köln had served several stints in Norway. The lower 6m-Rangefinder on top of the bridge had been replaced by a new FuMO-24 radar, the 20mm single FlaMG on the aft superstructure had been replaced by 20mm quads.
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On March 30th, 1945, she was attacked by British bombers while in Kiel harbor and sunk, only a few meters away from the place away where she was originally launched. However, because of the shallow water, her two aft turrets could be powered and armed from the land. Used against British troops, the wreck was blown up by the Germans when the position could no longer be held. After the war, Köln was broken up on-site from 1946-1956.

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Königsberg-class (K-class) light cruisers

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