The Second World War would find the fielding of history’s strongest battleships from the Imperial Japanese Navy. In their ranks were leviathan Yamato-class vessels at the pinnacle of naval engineering, along with their precursors, the Nagato-class dreadnoughts. Where the lead ship Nagato would survive the war to be destroyed as target practice in 1946, her sister ship, Mutsu, met a fate mysterious as well as tragic.
Suddenly, on June 8, 1943, the Battleship Mutsu exploded while anchored at Hashirajima, with the loss of all but a few of her crew. No reason for this calamity, which occurred in a supposedly safe harbor, ever came to light. An Allied submarine attack and either internal sabotage or negligence are only a few guesses.
Mutsu was the second and last Nagato-class dreadnought battleship commissioned by the IJN after World War I. She was named after the province of Mutsu. This ship had a distinguished career that included main relief efforts to the survivors of the Great Kanto earthquake in 1923. From 1934 to 1936, the modernization process focused mainly on armor and machinery; despite this, Mutsu still played a very small role in World War II.
By the beginning of hostilities, Mutsu had served for twenty years and undergone many significant remodeling; she was no longer the pride of the Japanese Navy and thus saw limited action. In December 1941, she was dispatched to the Bonin Islands to provide far-flung support to the fleet assaulting Pearl Harbor. After this mission, she had several roles in support, including towing the obsolete cruiser Nisshin for target practice by the Yamato.
Mutsu’s only real action was on August 27, 1942, during the Battle of the Eastern Solomons, where she fired four shells at an American reconnaissance aircraft. The fleeting action over, she was placed at Truk, where her anti-aircraft gunnery officers trained ground-based gunners. Mutsu returned to Japan in January 1943 and remained at Hashirajima until disaster struck in June.
On 8 June 1943, while being used for training exercises, Mutsu’s No. 3 turret magazine exploded at 12:13 PM. The force of the explosion was so tremendous as to cut the ship in two; it sank within less than five minutes of massive flooding. With the consequent huge flooding, the forward part of the ship capsized and sank, then the stern remained afloat for over 12 hours before finally going down. Of the 1,474 crew members and visitors on board, only 353 survived.
When the Mutsu went down in Japanese territory, the Imperial Navy was surprised. Suspicions of an Allied submarine attack were quickly dismissed. The incident was proclaimed a state secret by the Japanese government to avoid a large loss in morale. Remains of the dead were silently collected and cremated, survivors were transferred to different garrisons throughout the Pacific.
The initial investigation pointed out that human error could be the possible cause of the explosion, as the magazine of the ship was carrying 16-inch Type 3 “Sanshikidan” incendiary shrapnel anti-aircraft shells that had been responsible for the large fire at the Sagami arsenal. Another cause was soon announced: sabotage. According to the Japanese Navy, it concluded that a disgruntled seaman accused of petty theft and facing a court martial set a fire near the magazine as a ruse.
Not all historians accept this official version of events. Some believe that the Japanese Navy was attempting to cover up its ineptitude. The Mutsu was extremely outdated and full of flammable materials. An electrical fire somewhere near the magazine could have caused the explosion, but rather than admit to the ship’s obsolescence, the Navy found a convenient scapegoat.
Whatever the cause, the loss of Mutsu was a tragedy. Here her sailors, reconciled to death at the enemy’s hands, now died under particularly cruel circumstances in a supposedly safe harbor. The mystery surrounding what happened to Mutsu will never be known, a grim reminder of just how dangerous naval warfare can be.