This very high-performance gun was originally mounted in triple turrets aboard the Mogami class light (soon to be heavy) cruisers. However, upon their re-armament in preparation for the outbreak of hostilities, these turrets were replaced by 8-inch mounts aboard the four cruisers in question. Four apiece were then mounted aboard the then-building Yamato and Musashi. During mid-war refits, two apiece were removed to make way for additional 5-inch AA mounts. In addition, two more triple turrets were used aboard the Oyodo. The remaining mounts were intended for the Shinano and the rest of the never-completed Yamato class, as well as for Oyodo's sister-ship Niiyodo. Two of them were emplaced as shore-defense weapons near Sasebo and Kure, and two single mounts were emplaced near Tokyo.