Nagara-class cruiser
The six were a class of six light cruisers built for and operated by the Imperial Japanese Navy. The "Nagara"-class cruisers proved useful in combat operations ranging from the Aleutian Islands to the Indian Ocean throughout World War II. Most served as flagships for destroyer or submarine squadrons, and were deployed for transport or local defense missions. Towards the end of the war, the surviving vessels were increasingly obsolete and were retained as second-line units. The "Nagara" class was followed by the very similar . Background. A final three 5,500 ton class light cruisers authorized under the  8-4 Fleet Program were ordered by the Imperial Japanese Navy in 1920. Due to minor changes in design, primarily due to advances in torpedo technology, these three vessels were initially designated as "modified Kuma-class", or "5500-ton class Type II", before being re-designated after the lead vessel, . A second set of three vessels was authorized in late 1920. These final three vessels were initially to be named "Suzuka", "Otonase", and "Minase" until November 1921. Design. The "Nagara" class was the second class of light cruisers in the Imperial Japanese Navy based a standardized 5,500 ton displacement. In  terms of dimensions and performance, it is almost identical to the previous s; however, it was the first class of cruisers to be equipped with the new Type 93 Long Lance Torpedoes, which required a larger launcher. The "Nagara" class used the same hull, engine, and armaments layout as the "Kuma" class. The "Nagara"-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 same as the "Kuma" class. The propulsion system for the "Nagara" class was  based on four axial deceleration turbines with 12 boilers, providing . Ten boilers were designed to burn heavy oil, and the remaining two burned a mixture of coal and oil. The "Nagara"-class vessels were capable of , and a range of at . The main battery consisted of seven 14 cm/50 3rd Year Type naval guns 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. As with the "Kuma" class, the "Nagara" 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. A major difference from the "Kuma" class was in the configuration of the bridge, which incorporated an aircraft hangar. Initially, a platform was mounted above the No.2 turret, extending over the forward superstructure below the bridge. This was later replaced by an aircraft catapult. Even so, the arrangement proved unwieldy, and the catapult was moved to the rear of each ship, between the No.5 and No.6 turrets during retrofits in 1929-1934. The silhouette of the  bridges varied somewhat from ship to ship, as "Abukuma" has a rangefinder located on top of the bridge, whereas "Nagara" and "Isuzu" had instruments, "Natori" had a , and "Yura" and "Kinu" were equipped with instruments. In service modifications. Near the start of World War II, "Abukuma" and "Kinu" were scheduled to be fitted as flagships for destroyer squadrons, with the new Type 93 torpedoes. However, due to shortages, only "Abukuma" received the twin quadruple-mount launcher as planned, and her forward launchers were removed. After the start of the war, each of the vessels in the "Nagara" class was modified  and upgraded, especially to enhance anti-aircraft capabilities, but no two vessels were modified in the same way. To keep weight within design limits, the catapults were removed, and on almost all vessels, the No.5 and No.7 turrets were replaced by a twin-mount 12.7 cm/40 Type 89 naval gun and additional single and triple-mount Type 96 25 mm AA guns, wherever room permitted, supplemented by 13-mm machine guns. From 1943-1944, the five surviving ships in the class received radar. "Isuzu" was the only cruiser which underwent conversion into a dedicated anti-aircraft/anti-submarine cruiser. From  May–September 1944, all of her main guns were removed and replaced by a total of three Type 89 twin-mounted anti-aircraft guns, with a Type 94 fire-control system added to the foremast. Her Type 96 25 mm AA guns were increased to a total of 11 triple-mounts and 17 single-mounts. Her torpedo launchers were replaced by two quadruple launchers mounted in the stern, along with two depth charge rails. She was given a complete set of the latest radar, hydrophones and sonar. Ships in class. Six vessels were built in the "Nagara" class. None survived  the Pacific War.