Japanese battleship Musashi

Musashi, August 1942, taken from the bow

Musashi's main battery consisted of nine 45-calibre 46-centimetre Type 94 guns mounted in three triple gun turrets, numbered from front to rear. The guns had a rate of fire of 1.5 to 2 rounds per minute.[5] The ship's secondary battery consisted of twelve 60-calibre 15.5-centimetre 3rd Year Type guns mounted in four triple turrets, one each fore and aft of the superstructure and one on each side amidships. These had become available once the Mogami-class cruisers were rearmed with 20.3-centimetre (8.0 in) guns.[8] Heavy anti-aircraft defence was provided by a dozen 40-calibre 127-millimetre (5 in) Type 89 dual-purpose guns in six twin turrets, three on each side of the superstructure. Musashi also carried thirty-six 25-millimetre (1 in) Type 96 light anti-aircraft (AA) guns in triple-gun mounts, all mounted on the superstructure.[9] The ship was also provided with two twin mounts for the licence-built 13.2-millimetre (0.52 in) Type 93 anti-aircraft machine guns, one on each side of the bridge.[5]

While the ship was under repair in April 1944, the two 15.5 cm wing turrets were removed and replaced with three triple 25 mm gun mounts each. A total of twenty-one triple 25 mm mounts and 25 single mounts were added at that time, giving the ship a light AA armament that numbered one hundred and thirty 25 mm guns.[10]

Right elevation drawing of Musashi as she appeared in 1942

The ship's waterline armour belt was negligibly thinner than the Yamato's at 400 millimetres (15.7 in) thick and angled outwards 20 degrees at the top.[11] Below it was a strake of armour that ranged in thickness from 270 to 200 millimetres (10.6 to 7.9 in) over the magazines and machinery spaces respectively; it tapered to a thickness of 75 millimetres (3.0 in) at its bottom edge. The deck armour ranged in thickness from 230 to 200 millimetres (9.1 to 7.9 in). The turrets were protected with an armour plate 650 millimetres (25.6 in) thick on the face, 250 millimetres (9.8 in) on the sides, and 270 millimetres on the roof. The barbettes of the turrets were protected by armour 560 to 280 millimetres (22.0 to 11.0 in) thick, and the turrets of the 155 mm guns were protected by 50-millimetre (2.0 in) armour plates. The sides of the conning tower were 500 millimetres (19.7 in) thick and it had a 200-millimetre thick roof. Underneath the magazines were 50-to-80-millimetre (2.0 to 3.1 in) armour plates to protect the ship from mine damage. Musashi contained 1147 watertight compartments (1065 underneath the armour deck, 82 above) to preserve buoyancy in the event of battle damage.[12]

Musashi was fitted with two catapults on her quarterdeck and could stow up to seven floatplanes in her below-decks hangar. The ship operated Mitsubishi F1M biplanes and Aichi E13A1 monoplanes and used a 6-tonne (5.9-long-ton), stern-mounted crane for recovery.[13]

The ship was equipped with four 15-metre (49 ft 3 in) rangefinders, one atop her forward superstructure and one each in her main gun turrets, and another 10-metre (32 ft 10 in) unit atop her rear superstructure. Each 15.5-centimetre (6.1 in) gun turret was equipped with an 8-metre (26 ft 3 in) rangefinder. Low-angle fire was controlled by two Type 98 fire-control directors mounted above the rangefinders on the superstructure. Type 94 high-angle directors controlled the 127 mm AA guns, with Type 95 short-range directors for the 25 mm AA guns.[14]

Musashi was built with a Type 0 hydrophone system in her bow, usable only while stationary or at low speed.[15] In September 1942 a Type 21 air-search radar was installed on the roof of the 15-metre rangefinder at the top of the forward superstructure. Two Type 22 surface-search radars were installed on the forward superstructure in July 1943. During repairs in April 1944, the Type 21 radar was replaced by a more modern version, and a Type 13 early-warning radar was fitted.[10]

Musashi under attack by American carrier aircraft during the Battle of Leyte Gulf

Captain Toshihira Inoguchi relieved Asakura in command of Musashi on 12 August 1944 and was promoted to rear admiral on 15 October.[10] Three days later, she sailed for Brunei Bay, Borneo, to join the main Japanese fleet in preparation for "Operation Sho-1", the counterattack planned against the American landings at Leyte. The Japanese plan called for Ozawa's carrier forces to lure the American carrier fleets north of Leyte so that Kurita's 1st Diversion Force (also known as the Central Force) could enter Leyte Gulf and destroy American forces landing on the island. Musashi, together with the rest of Kurita's force, departed Brunei for the Philippines on 22 October.[25]

The following day, the submarine USS Dace torpedoed and sank the heavy cruiser Maya near Palawan. The destroyer Akishimo rescued 769 survivors and transferred them to Musashi later in the day.[26] On 24 October, while transiting the Sibuyan Sea, Kurita's ships were spotted by a reconnaissance aircraft from the fleet carrier USS Intrepid. Just over two hours later, the battleship was attacked by eight Curtiss SB2C Helldiver dive bombers from Intrepid at 10:27. One 500-pound (230 kg) bomb struck the roof of Turret No. 1, failing to penetrate. Two minutes later, Musashi was struck starboard amidships by a torpedo from a Grumman TBF Avenger, also from Intrepid. The ship took on 3,000 long tons (3,000 t) of water and a 5.5 degree list to starboard that was later reduced to 1 degree by counterflooding compartments on the opposite side. During this attack two Avengers were shot down.[10]

An hour and a half later, another eight Helldivers from Intrepid attacked Musashi again. One bomb hit the upper deck and failed to detonate; another hit the port side of the deck and penetrated two decks before exploding above one of the engine rooms. Fragments broke a steam pipe in the engine room and forced its abandonment as well as that of the adjacent boiler room. Power was lost to the port inboard propeller shaft and the ship's speed dropped to 22 knots (41 km/h; 25 mph). Anti-aircraft fire shot down two Helldivers during this attack. Three minutes later, nine Avengers attacked from both sides of the ship, scoring three torpedo hits on the port side. One hit abreast Turret No. 1, the second flooded a hydraulic machinery room forcing the main turrets to switch over to auxiliary hydraulic pumps, and the third flooded another engine room. More counterflooding reduced the list to one degree to port, but the degree of flooding reduced the ship's forward freeboard by 6 feet (1.8 m). During this attack, Musashi fired sanshikidan anti-aircraft shells from her main armament; one shell detonated in the middle gun of Turret No. 1, possibly because of a bomb fragment in the barrel, and wrecked the turret's elevating machinery.[10]

Musashi down by the bow after the air attacks, shortly before her sinking

At 13:31, the ship was attacked by 29 aircraft from the fleet carriers Essex and Lexington. Two Grumman F6F Hellcat fighters strafed the ship's deck and Helldivers scored four more bomb hits near her forward turrets. Musashi was hit by four more torpedoes, three of which were forward of Turret No. 1, causing extensive flooding. The ship was now listing one degree to starboard, and had taken on so much water that her bow was now down 13 feet (4.0 m) and her speed had been reduced to 20 knots (37 km/h; 23 mph). Two hours later nine Helldivers from Enterprise attacked with 1,000-pound (450 kg) armour-piercing bombs, scoring four hits. The ship was hit by three more torpedoes, opening up her starboard bow[27] and reducing her speed to 13 knots (24 km/h; 15 mph). At 15:25, Musashi was attacked by 37 aircraft from Intrepid, the fleet carrier Franklin and the light carrier Cabot. The ship was hit by 13 bombs and 11 more torpedoes during this attack for the loss of three Avengers and three Helldivers. Her speed was reduced to 6 knots (11 km/h; 6.9 mph), her main steering engine was temporarily knocked out and her rudder was briefly jammed 15 degrees to port. Counterflooding reduced her list to six degrees to port from its previous maximum of ten degrees. Musashi had been struck by an estimated total of 19 torpedoes and 17 bombs.[10][N 3]

Kurita left Musashi to fend for herself at 15:30, and encountered her again at 16:21 after reversing course. The ship was headed north, with a list of 10 degrees to port, down 26 feet (7.9 m) at the bow with her forecastle awash. He detailed a heavy cruiser and two destroyers to escort her while frantic efforts were made to correct her list, including flooding another engine room and some boiler rooms. Her engines stopped before she could be beached. At 19:15 her list reached 12 degrees and her crew was ordered to prepare to abandon ship, which they did fifteen minutes later when the list reached 30 degrees. Musashi capsized at 19:36 and sank in 4,430 feet (1,350 m) at 13°07′N 122°32′E.[N 4] Inoguchi chose to go down with his ship; 1,376 of her 2,399-man crew were rescued. About half of her survivors were evacuated to Japan, and the rest took part in the defence of the Philippines.[10] The destroyer Shimakaze rescued 635 of Maya's survivors from Musashi.[30]

On October 24, 2006, General Dominador Resos, Jr. (Ret), President of the Romblon Cultural Heritage Association, Inc. (ROCHAI), spearheaded The Commemoration of the Battle of Sibuyan Sea to honor the men who perished during the battle and to recognize the peace they had fought for. The event had become an annual multinational commemoration. It was reported that two years later, in 2008, Resos Jr. was in talks with Japanese personalities who were interested in locating the then-undiscovered remains of Musashi. Believing it had sunk in one piece, they had plans of refloating the battleship, towing it to a nearby island, and converting it into a war museum. However, the discovery of the wreck and Musashi's scattered remains in 2015 would prove that this feat could never be realized.[31]

During the more than 70 years since its sinking, various attempts have been made by shipwreck hunters to locate the wreck of the Japanese battleship but none of them succeeded. Musashi, like other Japanese warships, did not have its name on its sides, thereby making it more difficult for divers and shipwreck hunters to find her. The research team sponsored by Microsoft co-founder Paul Allen eventually found her after eight years of searching for the wreck, going through various historical records in different countries, and deploying the high-tech yacht Octopus and a remotely operated vehicle to aid them in their search. Allen announced in March 2015 that the team had indeed found Musashi under the Sibuyan Sea in the Philippines, some 3,000 feet (910 m) beneath the surface.[32][33]

The ship had been known to have sunk in one piece but exploded only after it was underwater.[34] Debris was scattered across the ocean floor. The bow section from the number one barbette forward is upright while the stern is upside down. The forward superstructure and funnel is detached from the rest of the ship and lies on its port side.[35] In the live streaming video tour conducted by the expedition team, a mount for the seal of the Imperial Japanese Navy—a chrysanthemum made out of teak, long rotted away—can be seen amid the debris. The video also showed damage made by U.S. torpedoes, including a warped bow and hits under the ship's main gun.[36] Other items found in the area of the wreck, as well as other features found in it led maritime experts to claim with 90% certainty that the wreck was Musashi.

To further confirm that the wreck was indeed Musashi, Shigeru Nakajima, an electrical technician on Musashi who claimed that he had survived by jumping overboard after the order to abandon ship, told the AP that he was "certain" of the wreck's identification upon seeing its anchor and the imperial seal mount. He also expressed his gratitude to the expedition team for having found the shipwreck.[32]

The discovery of the wreck beneath the surface of the Sibuyan Sea raised issues when the local government of Romblon (which has jurisdiction over the area where the wreck was found), though Governor Eduardo Firmalo stated that while he welcomed the discovery of the ship, the provincial government, and even the Philippine Coast Guard, were not aware that Allen and his team had an ongoing expedition in the area. In response to this, the Philippine Coast Guard also stated that foreign-owned vessels need clearance from the Philippine Foreign Affairs Department, the Customs Bureau, and the Immigration Bureau before they can enter Philippine waters.[37]

Although the discovery of the shipwreck is very important to the Japanese people because of the presence of more than 1,000 Japanese sailors' remains aboard the ship, the National Museum of the Philippines supported the Romblon Government by giving a statement—"Any further activity (pertaining to the shipwreck) shall be governed by established rules and regulations." It pointed out that the wreck site of Musashi, as stated by the law, is considered an archaeological site under the Philippine territory's jurisdiction, and it is "now giving priority to verifying the discovery, obtaining and sharing key information, facilitating the protection and preservation of the site, and formulating appropriate next steps."[37]