Furutaka - class cruiser The were a class of two Japanese heavy cruiser s which saw service during World War II . Both vessels of this class were sunk in 1942 . Design . The " Furutaka " class cruisers were the first heavy cruiser s in the " Imperial Japanese Navy " , also referred to as “ A class ” cruisers in the I . J . N . Like the Yūbari , their design was the work of Constructor Captain Yuzuru Hiraga , assisted by Lt . Cmdr . Fujimoto Kikuo . Designed to beat the U . S . Omaha - class cruiser s and the British Hawkins class cruiser s , they were as fast as the " Omaha " s ( and nearly 4 knots faster than the " Hawkins " class ) , while firing a heavier broadside , and carrying a larger torpedo battery , than either one . Their flush deck resulted in both weight savings and increased strength by allowing the hull ' s longitudinal members to be continuous . As with the " Yūbari " , the design featured side and deck armour integrated into the ship ' s structure , saving additional weight . Despite the weight - saving efforts , as built the " Kako " was more than 900 tons heavier than its design weight . As a result , draft was increased by more than 1 metre , subsequently reducing top speed , and the height of the belt armour above the waterline . The porthole s of the lowest - level crew quarters were near enough to the waterline that they needed to be closed when the ships were at sea , reducing ventilation and making the living spaces less habitable . They were the first of the I . J . N . cruisers to feature a substantial bridge , with 6 distinct levels , providing support for navigation , fire control , communication and command . Due to the high freeboard of these ships , mounting the torpedo tubes on the main deck would have caused the torpedoes to enter the water at too steep of an angle . Instead , they were mounted on the middle deck in 3 pairs of fixed tubes on each side . Captain Hiraga argued against this kind of mounting , concerned that during battle either a direct hit or fires could detonate the torpedoes , causing severe damage , as indeed happened with " Furutaka " of this class during WWII ; additionally , the cruisers " Mikuma " , " Suzuya " and " Chōkai " , all of which featured similar arrangements , would all be sunk or severely damaged by their own exploding torpedoes . Modernization . Japanese naval strategists since the early 1900s had planned for a defensive war in the Pacific , with the U . S . Navy as their main opponent . To take advantage of their superior long - range torpedoes , and offset the numerical superiority the U . S . Navy enjoyed , they extensively trained their crews in night torpedo tactics . In 1930 , the Naval General Staff , further concerned by the limitations on the size of their navy by the London Naval Treaty won approval for an extensive modernization program of the “ A class ” cruisers . Planned upgrades to the ships included the latest weapons , protection , fire control systems , and communication equipment . From 1931 to 1933 the two ships had their 4 original anti - aircraft guns replaced by improved 12 cm HA electro - hydraulically operated guns , with directors and range finders for them . The original airplane takeoff platform was replaced with a catapult for a reconnaissance seaplane . They were substantially rebuilt in 1936 - 1937 ( " Kako " ) and 1937 - 1939 ( " Furutaka " ) as follows : The 6×1 20 cm . main battery was replaced by 3 twin turrets housing the / 50 - cal guns . Light antiaircraft protection was augmented with 8 25 mm machine guns in 4 twin mounts . The 6 pairs ( 3 per side ) of fixed torpedo tubes mounted on the middle deck were replaced with 2 quadruple mounts using the powerful Type 93 torpedo , located on the upper deck , one on each side of the catapult . The bridge structure was completely rebuilt to accommodate the latest rangefinders and fire control equipment for the main battery , antiaircraft and torpedoes . Platforms were redesigned for aircraft spotters . The twelve original mixed - fuel boilers were replaced by 10 large oil - fired units , along with a redesign of all the boiler rooms , and replacement of coal bunkers with fuel - oil tanks . All of the new equipment resulted in increased electrical power requirements , so 3 more generators were added to increase power output from 315 kW to 885 kW . The above modifications added 560 tons to the ships . To prevent the draft from increasing even more , and to improve stability , bulges were added , simultaneously enhancing antitorpedo protection . As a result , the ships ' beam was increased to .