The Second World War saw the Imperial Japanese Navy field the heaviest battleships ever constructed. The enormous pair of Yamato-class ships which fought and died in the Pacific were true monsters, the last of a dying breed.
The Yamato were joined by their predecessors, two huge Nagato-class dreadnoughts which had served their country faithfully since the lead ship put to sea in 1919. The Nagato indeed would survive World War Two, doomed to be destroyed by the US as target practice in 1946.
However her sister ship, the Mutsu, had an altogether stranger fate. Anchored at Hashirajima on June 8, 1943, the vessel suddenly exploded, claiming the lives of the majority of its crew members.
The ship had sat out much of WW2 and was almost entirely undamaged, making her fate even more shocking. To this day the exact cause of the Mutsu’s destruction remains a mystery.
How could this have happened? Was she attacked by an Allied submarine, a victim of negligence, or did something even more sinister befall her?
A Shocking Fate
Mutsu, designated as 陸奥 in Japanese, was the second and final of the Nagato-class dreadnought battleships, commissioned by the Imperial Japanese Navy (IJN) in the aftermath of World War I. Named after the province of Mutsu, the vessel had an eventful career, including a pivotal role in delivering aid supplies to survivors of the Great Kantō earthquake in 1923.
Following this the ship remained in service but saw little action. From 1934 to 1936 she underwent modernization and received enhancements to her armor, machinery, and a reconstructed superstructure fashioned in the pagoda mast style: she was once again a formidable battleship.
Mutsu may have been considerably smaller than her Yamato successors, but she was still immense, measuring 201 m (660 ft) between perpendiculars and 216 meters (708 ft) overall. Mutsu boasted a beam of 29 meters (95 ft) and a draft of 9 meters (29 ft 6 in). Displacing 32,720 tons (32,200 long tons) at standard load and 39,116 tons (38,498 long tons) at full load. She had first put to sea with 1,333 officers and enlisted personnel. After her various upgrades she was home to 1,475 souls.
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By the start of World War Two Mutsu had been in service for two decades and had already seen several major remodels and retrofits. She was, in all honesty, no longer the crown jewel of the Japanese Navy as she had once been, and as a result she saw limited action during the war.
In December 1941 she was sent to the Bonin Islands alongside several other Japanese battleships and a light carrier. Their mission was to offer distant support to the fleet that had been tasked with attacking Pearl Harbor, a mission that lasted for 6 days.
Following this mission, she was tasked with towing an obsolete cruiser, Nisshin, so that it could be used for target practice by Japan’s newest battleship, the Yamato. She was given the honor of bringing her successor online.
The following June Mutsu joined Japan’s 1st Fleet for the Battle of Midway against the US Navy. The Battle lasted for three days, and the Mutsu never saw any action after a Japanese plan to lure American forces into an aerial ambush failed. Following the battle Mutsu acted as a transport ship, transferring survivors from the battle to Hashirajima.
Mutsu was transferred yet again on 14 July, this time to Division 2 and then again to the 2nd Fleet on August 9. Two days later she departed Yokosuka with cruiser reinforcements to escort Japanese destroyers destined to support the Guadalcanal Campaign. They finished this mission on 17 August.
Three days later Mutsu nearly got to see some action. Mutsu, a heavy cruiser, and some destroyers were sailing to meet up with the 3rd Fleet when they stopped to search for the USS Long Island which had been spotted in the area. Their search failed.
The only real action Mutsu saw came on 27 August during the Battle of the Eastern Solomons. The ship had been assigned to the support force and fired four shells at an American recon aircraft. It was the only time she got a shot off during the entire war.
Following this excitement Mutsu sailed to Truk where its AA gunnery officers were tasked with training ground-based anti-aircraft gunners. Mutsu stayed in Truk until 7 January 1943 when she set sail for Japan. She then stayed in Hashirajima until April 13.
Disaster Strikes
Mutsu had had an uneventful war but that was about to change. On 8 June she was once again stationed at Hashirajima and was being used for training exercises. That day she had 113 flying cadets and 40 instructors onboard who were familiarizing themselves with the ageing ship.
At 12.13 the magazine attached to her No. 3 turret exploded without warning. The explosion took out everything surrounding it and the blast was so destructive it cut the ship in two. This was followed by massive flooding as seawater rushed in, filling the machinery spaces.
The 150-meter (490 ft) forward section of the ship then began to capsize and sink. Following this the 45-meter (148 ft) stern section upended but managed to stay afloat for over 12 hours, sinking at 2 am the following day.
Nearby ships rushed to the aid of Mutsu’s crew. In total 353 survivors were rescued out of 1,474 total members and visitors. Casualties amounted to 1,121 killed by either the initial explosion or drowning. Of the cadets visiting that day only 13 survived.
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The destruction of Mutsu in Japanese territory caught the Imperial Navy off guard. As soon as rescue operations were underway a search began for Allied submarines, but none were found. Fearing that her destruction could cause a major loss in morale, the government declared the Mutsu’s destruction a state secret.
The bodies of the deceased were quietly gathered up and burned in mass cremations. The cover-up was so extensive that even though Captain Teruhiko Miyoshi’s body was found on June 17, his wife wasn’t notified of his death until January 1944. Those who had survived were split up, told to keep quiet, and reassigned to garrisons spread across the Pacific.
Initially, it was suspected that human error had caused the explosion. At the time of the accident, the ship’s magazine contained 16-inch Type 3 “Sanshikidan” incendiary shrapnel anti-aircraft shells. This ammunition had caused a massive fire at the Sagami arsenal several years prior when they had been stored improperly. As a precaution, following Mutsu’s destruction, this type of ammo was removed from every other ship in service.
However, a different cause was soon announced: sabotage. On 25 June, the Japanese Navy released a preliminary conclusion stating that the explosion had been set by a disgruntled seaman. He had been accused of petty theft and was due to face a court martial the day of the explosion. It’s believed he set a fire near the magazine to serve as a distraction.
Not all historians buy this official version of events. The accused’s name was kept secret, but Naval officials claimed his body had been found among the wreckage. Whoever he was, he made for a fitting scapegoat.
Some believe that the Japanese navy was attempting to cover up its own ineptitude. Mutsu was severely out of date and compared to the modern warships of other nations contained enormous amounts of flammable materials. Despite multiple refits, it’s also likely the ship’s electrical wiring was out of date.
This had led some to conclude an electrical fire broke out next to the magazine. It got out of hand and heated the magazine to a temperature at which the primers of the ammunition went off inside. Rather than admit its ships were old and out of date, the navy found a scapegoat.
Sabotage or accident the sinking of the Mutsu was a tragedy. Her sailors knew the risks when joining the war but expected death to come at the hands of the enemy. Instead, death came in a different, and in many ways a crueler, form.
Top Image: The explosion aboard the Mutsu, which split the mighty ship in two, shockingly occurred in a supposedly safe harbor. Source: KHBandak / Adobe Stock.
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