The were a class of five light cruisers built for and operated by the Imperial Japanese Navy (IJN). The Kuma-class cruisers proved useful in combat operations ranging from the Aleutian Islands to the Indian Ocean throughout World War II.
The Kuma-class was followed by the very similar .
Despite the success of the high speed light cruiser design, the Imperial Japanese Navy realized that they would be outgunned by the larger US Navy and the Dutch Java-class of light cruisers then under development. In addition, the Tenryū-class vessels, with a maximum speed of 33kn, were unable to keep up with the newer Japanese destroyers, such as the, which had a design speed of .[1] At the end of 1917, plans for an additional six Tenryū-class vessels, plus three new-design 7200 ton-class scout cruisers were shelved, in place of an intermediate 5,500 ton-class vessel which could be used as both a long-range, high speed reconnaissance ship, and also as a command vessel for destroyer or submarine flotillas.[2]
With the development of the long range oxygen-propelled Type 93 "Long Lance" torpedoes in the 1930s, the Imperial Japanese Navy General Staff drafted plans to create a special "Night Battle Force" of torpedo cruisers. The idea was based on Japan's success in the naval Battle of Port Arthur in the Russo-Japanese War. As the new Type 93 torpedoes had a range longer than that of contemporary battleships' main battery, the concept was to have a high speed strike force attack an enemy fleet at night with a massive and overwhelming barrage of torpedoes. Major surface combatants would follow up at dawn to finish off the wounded enemy.
Ōi and Kitakami were subsequently modified with ten quadruple mount torpedo launchers (a total of 40 tubes), arranged in two broadside rows of five, i.e. 20 per side. The ships were assigned to the CruDiv 9 of the IJN 1st Fleet. However, the rapid development of naval aviation and submarine warfare in the 1930s quickly made this plan obsolete. In January 1942, Chief of Staff Rear Admiral Matome Ugaki expressed strong disapproval of the newly remodeled torpedo cruisers and urged a revision to the Navy's tactics.[3] While the Imperial Japanese Navy General Staff debated the issue, Ōi and Kitakami were converted to high speed transports, with, and Kitakami was subsequently converted into a carrier for kaiten suicide torpedoes.
The Kuma-class hull design was based on a 5,500 ton nominal displacement, with a high freeboard and light bridge structure, behind which was a tripod mast with the fire control platform and two searchlights. The design proved so versatile that it became the standard upon which all future light cruisers in the Japanese navy would be based.[1]
The propulsion system for the Kuma class was based on four axial deceleration turbines with 12 boilers, providing 90000hp. Ten boilers were designed to burn heavy oil, and the remaining two burned a mixture of coal and oil. With improvements in geared-turbine engine technology, the Kuma-class vessels were capable of the high speed of 36kn, and a range of 9000nmi at 10kn.[2] The silhouette of the Kuma class was discernible by its three smoke stacks, with the stacks flaring out in a trumpet shape.
The number of 14 cm/50 3rd Year Type naval guns was increased from four on the Tenryū class to seven on the Kuma class, centerline mounted in individual gun turrets, (two fore, three after and one on either side of the bridge). The positioning meant that only six of the guns could be brought to bear in a broadside.[2] As with the Tenryū class, the Kuma class remained highly deficient in anti-aircraft protection, with only two 8 cm/40 3rd Year Type naval guns and two 6.5 mm machine guns. Provision was made for 48 naval mines. The two triple torpedo launchers on the Tenryū class was changed to four double launchers, placed in pairs so that four torpedoes could be fired on each side. Eight reloads were also provided.[1]
Kiso was unique in that it had both a forward and aft flat surfaced superstructure, with a rotating floatplane take-off platform located aft. The platform appears to have never been used, and was removed in 1922, but her superstructure retained the shape of the hangar.
From 1931-1932, provision was made for a catapult to launch one floatplane (typically a Kawanishi E7K1 "Alf" floatplane) for scouting purposes on Kuma and Tama. The catapult was situated aft, in between the No.5 and No.6 turrets.[1]
From 1933-1934, the ships were renovated with a modified superstructure, replacing the canvas sides of the bridge with steel plate, and building a rangefinder tower behind the bridge was with either an 11.5feet or 13feet rangefinder. Kiso was also given anti-rain caps on her two forward stacks, which gave her a unique appearance.[1]
By 1941, the 8-cm Type 3 guns were replaced by a twin-mount Type 96 25 mm AA guns, and the 6.5 mm machine guns were upgraded to 13.2 mm.[2] All of the ships in the Kuma class were progressively upgraded during the Pacific War. The modifications varied from vessel to vessel, but consisted of removing the aircraft catapult and at least one of the main 140-mm turrets, and replacing with twin or triple-mount Type 96 25-mm anti-aircraft guns. From 1943-1944, Kiso and Tama were given a twin turret with 12.7 cm/40 Type 89 naval guns. Kiso, Tama and Kitakami were the only in the class to receive radar.[1]
In August 1941 Ōi, Kitakami and Kiso were to undergo a conversion to torpedo cruisers to form a special torpedo attack squadron, but not enough Type 92 quadruple torpedo mounts were available so only the first two were converted,[4] both ships three aft turrets were replaced by ten quadruple torpedo mounts, five per side, with a total of 40 torpedoes. In August 1942, they were modified into fast transports, with all of the torpedo tubes removed and replaced by Daihatsu class landing craft, with depth charge racks and two Type 96 triple-mount anti-aircraft guns.[1]
After Kitakami was damaged in 1944, she was converted into a kaiten carrier, with all of her armament removed, and replaced by two Type 89 single gun turrets (fore and aft), a total of 67 Type 96 anti-aircraft guns(12 triple, 31 single), two depth charge racks and eight Model 1 Kaiten. Removal of the aft turbine engines reduced her speed to 23 knots.[1]
Five vessels were built in the Kuma class. Only one (Kitakami) survived the Pacific War.