Japan’s first post-WWI battleships, the Nagatos were the first battleships to be armed with 16-inch guns. Whereas all previous post-Dreadnought Japanesecapital ships had either been built overseas or with foreign assistance of some degree, the Nagatos were purely domestic products. Reaching over 26 knots on trials, they were the fastest battleships of the day.
The mid-1930s saw both Nagatos undergo a thorough rebuilding; the stacks were combined to a single unit, and “pagoda” masts appeared. protection was greatly enhanced in most respects, but this could only be achieved at the cost of increased displacement. New powerplants helped to compensate for this, but this only kept the speed at previous levels. The main armament was retained, but rebuilt with greater elevation capability.
Despite having been rebuilt to such a degree, the Nagatos were to see little combat during World War II, as by that time their once-impressive speed was not sufficient to keep up with fleet carriers. While laying in Hiroshima Bay on July 3, 1944 Mutsu suffered a tremendous explosion in the vicinity of the No.3 turret, killing all but 353 of the 1,474 men aboard her. The ship was split in two; the forward section immediately sank, but the aft portion floated for several days before heading to the bottom as well. Submarine attack was at first suspected, but Mutsu’s loss was later attributed to an ammunition explosion. The IJN actually intended to recover and rebuild the ship, but such thoughts were soon put to rest. The wreck underwent salvage in 1970-78, resulting in the recovery of many artifacts, including the No.4 turret.
Nagato suffered damage from an air attack on 26 October 1944 at Leyte Gulf, and with oil supplies rapidly drying out, spent the remainder of the war at Yokosuka as a stationary battery, with much of her AA armament moved ashore. She took further airstrike damage, but remained afloat at the end of the war, the only Japanese battleship to do so. She was earmarked by the USN for use as a target ship for the 1946 Crossroads A-bomb tests; an American crew managed to get the barely seaworthy ship to Bikini, although part of the voyage had to be made under tow. Nagato survived the initial Able bomb dropped by a B-29, but the underwater Baker shot spelled her doom, although she would linger after the blast for a time before finally capsizing.