Design B - 65 cruiser Design B - 65 was a class of Super Type A cruiser s planned by the Imperial Japanese Navy ( IJN ) before and during World War II . As envisioned by the IJN , the cruisers were to play a key role in the Night Battle Force portion of the " Decisive battle " strategy which Japan hoped , in the event of war , to employ against the United States Navy . Begun in 1939 , plans were far enough along that tests were conducted with the main armament and against the underwater protection . Even though the ships were approved for construction under a 1942 fleet replenishment program , the prioritizing of aircraft carriers and smaller ships due to the war , followed by Japan ' s defeat , killed any chance of the B - 65 ' s construction . Mission and plan . The Japanese navy ' s experience in the Russo - Japanese War of 1904 - 1905 , especially the Battle of Tsushima , strongly influenced the creation of the IJN ' s " Decisive Battle " doctrine , which guided the development and deployment of the IJN ' s battle fleet into World War II . The Decisive Battle concept was the IJN ' s primary strategy for defeating the navies of the major Western powers , such as Great Britain or the United States , in the event of war . The strategy consisted of four main components : a decisive surface fleet engagement determined by big guns , attrition tactics against a numerically superior enemy , a reliance on quality over quantity in naval weaponry , and the employment of nighttime torpedo attacks . After the Washington Naval Treaty of 1922 and the London Naval Treaty of 1930 , each of which placed restrictions on the size of the IJN ' s fleet in comparison with the fleets of the western powers , notably the United States , the decisive battle strategy received increased emphasis within the IJN . In 1936 , the IJN formed the Night Battle Force ( Yasen Butai ) . As designed , the night battle force was to attack the hypothetical enemy ' s , usually envisioned by the Japanese to be the US Pacific Fleet , outer defense ring of cruisers and destroyers at night . After cracking the outer defense ring , IJN cruisers and destroyers were to launch torpedo attacks on the enemy ' s battleships . What remained of the enemy fleet was then to be finished - off by the IJN ' s main battleship line the following day . The IJN assigned one division of fast battleships or battlecruisers to give additional firepower to the nocturnal attacks . The s were initially assigned to this role and were upgraded to fast battleships over a seven - year period from 1933 - 1940 . The IJN planned to eventually replace the four " Kongō " battleships with four heavy , " super " cruisers . As envisioned by the IJN in 1936 , these ships , the B - 65 cruisers , would mount 12 - inch guns , carry armor designed to withstand hits from 8 - inch shells , and be capable of speeds up to 40 knots . They would be designated as " super - A - class cruisers " to signify their greater status than the A - class ships ( heavy cruiser s ) . The plan for the cruiser class was finalized as part of the IJN ' s Circle Five and Circle Six warship construction plans of 7 January 1941 . The plan called for six B - 65s to be built in two increments , with the first two to be constructed in Circle 5 with the remainder in Circle 6 . By this time , Japanese intelligence had learned the specifications for the United States Navy ' s large cruisers , which had been authorized for creation by the passage of the Two - Ocean Navy Act and ordered on 5 September 1940 . The Japanese believed that these ships would form part of the American battle fleet ' s screen in times of war . Thus , the B - 65s were now intended to counter the threat posed by the " Alaska " - class cruisers . Design . Design work on the B - 65s began in 1939 . Preliminary plans for the new class were finished by September 1940 , and they were far enough along that tests of the lower protection — the armor intended to counter any shell that fell short but still hit the ship ( albeit underwater ) and torpedo es — and main armament were conducted from 1940 to 1941 . These plans called for ships that bore a striking resemblance to the s , with the same " clipper bow , flush - deck construction , and a generally similar superstructure " , albeit at a reduced size . Nine / 50 caliber guns in three triple turrets , sixteen / 65 caliber dual - purpose gun s in dual mounts on either side of the superstructure , twelve paired anti - aircraft gun s , four machine guns , and eight torpedo tubes were to be the primary weapons of the cruiser . The weight of the main battery turrets was to be around , with of that devoted to armor ; however , no plans of how this latter figure was to have been distributed has survived . The cruisers were to be protected by belt armor sloped at and deck armor . Four geared turbine sets would have generated about 42 , 500 shp each ; for a total of about 167 , 674 shp , enough to power the ships through the water at , faster than the " fundamental design requirement " of . In an attempt to counter the " Alaska " - class cruisers guns , a proposal to increase both the main battery to six and armor protection to resist against the same was put forth . However , the increase in displacement ( to almost ) and reduction in performance this entailed meant that nothing came of the proposed changes . Final plans and cancellation . As war with the United States loomed in 1941 , the navy found that it had a more pressing need for aircraft carriers and auxiliary vessels . This need , plus a desire to complete the ongoing Circle Three and Four construction programs , delayed initiation of the Circle Five plan . Following the Japanese navy ' s defeat at the Battle of Midway in June 1942 , the Circle Five plan was significantly revised and Circle Six was postponed indefinitely . The new plan still called for the construction of two ships of Design B - 65 , which were given the hull number s 795 and 796 with projected commissioning dates of 1945 and 1946 , respectively . As the war progressed , however , strategic requirements further delayed the plans for the two cruisers . In the end , the B - 65s ' plans were never finalized and no contracts for their construction were ever placed .