The Mogami, Mikuma, Suzuya, and Kumano were classifed light cruisers when built but were heavy cruisers by any real definition. As built they were unstable and had many structural defects and were decomissioned and rebuilt to correct these defects. The original armament of 15 6.1" guns was replace in 1939-1940 with 10 8" guns. The Mogami was given an unsatisfactory conversion to seaplane tender during the war. Mikuma was sunk at Midway, Mogami and Suzuya on October 25, 1944 and the Kumano on 25 November, 1944.
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