Displacement: 62,315 tons/63,312 tonnes (standard); 69,998 tons/71,110 tonnes (full load)
Length: 862ft 11in/263m (oa); 800ft 6in/243.9m (pp); 839ft 10in/256m(wl)
Beam: 121ft 1in/36.9m
Draught: 35ft 7in/10.86m (mean)
Machinery: twelve Kampon boilers; 4-shaft Kampon geared turbines
Bunkerage: 6,300 tons oil Performance: 150,000shp = 27.46kts
Range: 7,200nm at 16kts
Protection: main belt 16.1in; blkhds 11.8in; main deck 7.9in-9.1in; barbettes 21.5in; CT 19.7in max. Shinano and later ships: main belt 15.7in; decks 7.5in; barbettes 20.8in
Guns: nine (3x3) 18.1in; twelve (4x3) 6.1in; twelve (6x2) 5in DP; twenty-four (8x3) 25mm; four 13mm (Shinano and later ships: twelve (6x2) 3.9in DP in lieu of the 5in DP)
Torpedo tubes: nil
Aircraft: seven, catapults two
The 8-8 Programme referred to earlier had continued with the construction of two more battleships of the Tosa class, authorised under the 1918 Programme, Tosa and Kaga, both of which had been laid down in 1920. Armed with ten 16in guns and displacing 38,500 tons, they would have been powerful additions to Japan's battle fleet had they been completed as intended. Unfortunately for the Japanese, however, their construction coincided with the deliberations of the Washington Conference and as a result they had to be cancelled, despite being well advanced towards completion. Tosa in fact was used as a target in shell design development in 1924, providing important data for the later Yamato design, until sunk in the Bungo Straits by gunfire on 9 February 1925. Her sister was converted to an aircraft carrier, completing in her new role in March 1928, having escaped destruction under the terms of the Washington Treaty because of the great earthquake of Sep
tember 1923. This event wrecked the ship actually intended for conversion, Amagi. She was the name ship of a class of four battlecruisers of 40,000 tons and armed with ten 16in guns, also part of the 8-8 Programme, the first two of which, Amagi and Akagi, had also been authorised under the 1918 Programme. Laid down in December 1920, they were followed by two more ships, Atago and Takao, on the ways a year later. These too were suspended on 5 February 1922 and subsequently cancelled as the result of the Washington agreements, but Japan was allowed to convert two into carriers. But Amagi was destroyed by the earthquake and replaced by Kaga, and the later pair were scrapped on the stocks. Two more classes of capital ship in the 8-8 Programme also became casualties to the Washington Treaty: the four Owari-class fast battleships armed with ten 16in and displacing 41,400 tons, which were ordered but never laid down, only two even receiving names, and the four projected unnamed ships of the subsequent class, which were to have displaced 47,500 tons and be armed with 18in guns in four twin turrets.
So of the eight battleships and eight battlecruisers of the 8-8 Programme, only the two Mutsus came to fruition, leaving Japan militarily and politically dissatisfied with her treatment by the great powers, and this discontent was to have a considerable effect on her later policies.
During the years immediately subsequent to the signing of the Washington Treaty, Japan, like all the other powers, continued to study new designs in anticipation of the expiry of the battleship construction 'holiday' which was due on 31 December 1931. Studies to replace the ageing Kongos began in earnest early in 1930, when two 35,000-ton designs were considered, both of which had the same basic dimensions and were armed with ten 16.1in guns, but differed in the disposition and calibre of the secondary armament. But the London Naval Treaty of 1930 extended the building 'holiday' for battleships until 31 December 1936, which meant the suspension of these design studies and forced Japan, no less than the other naval powers, into expensive modernisation programmes for older ships which were not necessarily an effective or economical solution.
In 1934 the Japanese, angered by the attitude of the League of Nations in regard to their incursion into Manchuria, withdrew from that organisation and decided that they would no longer be fettered by imposed restrictions on their defence capabilities. They now embarked on a path of design studies unrestricted by considerations of treaty requirements. Which would eventually lead to the commissioning of the largest and most heavily armed battleships ever built. The 35,000-ton displacement limit was ignored and a main armament of either 16in or 18in was chosen for all subsequent design studies. The basis for the Japanese considerations was a forecast of the most powerful US battleship design that could get through the Panama Canal, this being a prime US requirement, and to design a ship which was superior to it. The Japanese design would be restricted only by available building, harbour and docking facilities, and in the end even this was an elastic concept.
During the next two years, some twenty-four separate design studies were investigated, ranging in displacement from 49,000 tons to more than 68,000 tons and armed with various combinations of 16in and 18in guns, many of which were arranged as in Nelson, i.e., all forward. Both steam and diesel propulsion were considered, with speeds between 24 and 31 knots. By October 1935, i.e., well before the final international abandonment of treaty restrictions, the definitive design parameters of the new class had been established: nine 18in in three triple turrets, a speed of 27 knots utilising combined steam and diesel power, armoured against 18in shells. Detailed planning took a further nine months or so during which time it became evident that there were design defects in the current main propulsion diesel engines then in service. As the diesels for the new battleship would be developments of these, it was realised that if problems were to arise in service, the removal and replacement of defective engines from a battleship, where thick armour plate covered the engine rooms, would be a totally different matter from dealing with a submarine depot ship which was currently experiencing these problems. So the final scheme, completed in March 1937, was totally steam turbine powered.
The displacement was 62,000 tons, (standard), 67,000 tons full load, on a hull almost 840 feet in length on the waterline. Beam was considerable at 121 feet such dimensions requiring enormous extensions to yard capacities before construction could begin. Slips had to be lengthened and strengthened (at Mitsubishi) and graving docks constructed (at Yokosuka and Kure) in which to build the ships, and all manner of ancillary work had to be undertaken before construction could begin, all of which had to be carried out in conditions of utmost secrecy. Such was the success of these measures that the Allies never knew full details of the design until after the surrender, not even that they were armed with 18in and not 16in guns! Electric welding was used as well as riveting, despite the bad experiences of early welding on cruisers and destroyers. The hull was given a bulbous bow to reduce hull resistance and increase speed, which partly countered the negative aspect of the unfavourable length to beam ratio.
The protective scheme was on the all or nothing principle in that all armour was confined to the main citadel, with some small exceptions. The vertical armour included a 410mm side belt (note that Japan had now adopted metric measurements) inclined 20° outwards from bottom to top, approximately 5.8m in depth, of which about one half was below the design load waterline. The lower edge of this belt was chamfered down to match the lower armour belt, which was 270mm thick at its upper edge in the way of the magazine spaces and 200mm abreast the machinery spaces. This belt was also inclined but at 15° and extended down to the outer plating of the double bottom space, tapering down to 75mm at its foot. The side armour extended between the two transverse armoured bulkheads, which were 300mm forward and 300mm (upper), 270mm (lower) aft. Unusually, these two bulkheads were themselves inclined outwards from bottom to top by 25°. There was a torpedo bulkhead of 100mm thickness. The horizontal protection included a main deck of 200mm, increasing to 380mm (but perforated) over the boiler uptakes, the sides of which abutted the top of the side belt. This deck was flat across the beam except that outboard of the outermost longitudinal bulkhead, a small downwards incline was incorporated, where the thickness was increased to 230mm. Below this deck was a 9mm splinter barrier. Between frames 72 and 112, and 162 and 183, i.e., the magazine spaces, 80mm armour was applied to the floors of these spaces to give protection from underwater explosions. Armoured boxes up to 360mm and 300mm protected the main and auxiliary steering machinery respectively. The upper deck had 35mm-50mm armour to act as a fuse initiator in case of bomb hits, but mainly to withstand the blast effects of firing the 18in guns. Main turret barbettes had 380mm-560mm and the turrets themselves, 650mm faces, 250mm sides, 190mm rear and 270mm roofs. But the secondary armament had only 50mm protection. The conning tower was 500mm. The weight allocated to protection was 22,534 tons, or 33.1 per cent of the designed displacement. From the design waterline to the bottom plating was a torpedo bulge with maximum depth of about 2.8m outside the side belt. This armour scheme was designed to confer protection from 18in shells at ranges from 21,870 yards out to 32,800 yards.
As has been explained, the main propulsion plant was a geared steam turbine installation, driving a four-shaft arrangement. There were twelve Kampon boilers each in a separate space, occupying three transverse compartments of the ship, the centre-line of which was divided by a double longitudinal bulkhead acting also as a pipe and cable space. This bulkhead extended well beyond the transverse armoured bulkheads and effectively divided the ship into two. The four engine rooms were abaft the boiler rooms, disposed across the beam of the ship, the inner shaft machinery being farther forward than the wing spaces. The machinery developed 150,000shp for a designed speed of 27.5 knots. On trials Yamato achieved 27.4 knots on a displacement of 69,500 tons with 153,553shp, but she is reported as having made 28.05 knots in June 1942.
The main armament consisted of the 18.1in gun known as the 46cm Type 94, a 45cal weapon referred to for security reasons as the 40cm Type 94. This gun fired a 3,2191b AP shell to a range of 45,960 yards at 45°. Each triple turret weighed 2,470 tons complete. Each gun was in a separate cradle and could thus elevate independently. Elevation was hydraulic, training electric. Interestingly, special shells were provided for use in barrage AA fire by these guns.
The secondary armament comprised four triple 6.1in, one each superfiring on Nos. 2 and 3 turrets and the other pair on the beam abreast the funnel. The gun was the 15.5cm 3rd Year Type, firing a 123lb shell to a range of 29,960 yards. Although most successful in their designed role, these guns were LA weapons and were unsuccessful in HA applications. Because the secondary battery could not be counted on for long-range AA defence, it was necessary to fit a tertiary battery of 5in DP weapons, the standard 12.7cm Type 89, in twelve twin mountings, six per side, grouped amidships. The light AA battery was the weakest point in the design because the standard 25mm gun did not have the range or punch to cope with modern aircraft, but nothing else was available. Eight triple mounts was the as-fitted outfit on completion. The pair of twin 13mm machine-guns fitted on the bridge was even more useless for defence, but this was not appreciated at the time and Japan was no different from the other powers in this respect. No torpedo armament was fitted, but comprehensive arrangements were made for the operation of aircraft. Two 59ft catapults were fitted on the quarterdeck port and starboard.
The forecastle deck was extended aft of No. 3 turret to form an aircraft handling platform, with rails and turntables for the marshalling of the aircraft. A lift from the after end of this deck communicated with the hangar below the quarterdeck, which could accommodate seven aircraft but in practice four was the norm. The aircraft shipped was usually the two-seat Mitsubishi F1M2 'Pete'.
Main battery fire control was exercised by the Type 98 LA system with a director position atop the foretower with a 49ft range-finder and a secondary position aft fitted with a 33ft range-finder. All three 18in turrets also carried 49ft range-finders. Secondary battery control was by means of four directors each equipped with 15ft range-finders, while the 5in AA battery was controlled by the Type 94 HA system, which was reputed to compare very favourably with the USN's Mk 37 DP system.
Two ships, Yamato and Musashi, were authorised in 1937, and two more, Shinano and one unnamed (No. 111), in 1939. Under the 1942 Programme a fifth ship, No. 797, was projected, but no contract was placed for this unit. The last three of these, i.e., from Shinano, were to have differed in certain respects such as protection. Their main belt was to have been 400mm, main deck 190mm and turret protection reduced. They were to have shipped sixteen to twenty 4in DP (10cm/65 Type 98) guns as heavy AA, similar to those installed in the Akizuki-class destroyers, this gun being considered Japan's best AA gun.
These, with the exception of Shinano, totally converted to an aircraft carrier, were limited to the armament. The need to increase the heavy AA defence led, in the autumn of 1943, to the removal of the beam 6.1in triple turrets in both ships, to be replaced by an additional three twin 5in DP on each beam. But mountings were only available for one ship and Yamato received them, leaving Musashi to ship extra 25mm mountings in lieu. The 25mm outfits were progressively augmented, Yamato having thirty-six in 1943, ninety-eight by April 1944, 113 by July that year and finally 150, sixty-three of which were single and the remainder triple. Musashi had thirty-six 25mm in 1943, fifty-four early in 1944, 115 in April 1944 and 130 in July 1945, only twenty-five of which were in singles as compared to her sister. Neither ship was fitted with radar at completion, Type 21 sets being installed on the foretop in the autumn of 1942. Early in 1943 each was also fitted with two Type 22 sets, one on each side of the bridge tower, and in 1944 Type 13 surface search sets were fitted as well.
Yamato ran trials in the Inland Sea in November 1941 and finished final fitting out at Kure before being commissioned in December 1941 for the 1st Battle Squadron, attached to the Combined Fleet. She saw no operational service until the early summer of 1942, having become Flagship of the Combined Fleet on 12 February that year. On 29 May she sailed from Hashirajima Bay accompanied by Nagato and Mutsu at the start of the Midway operation, but because of the disposition of the Japanese fleet, the battleships played no part in the subsequent debacle and were unable to prevent the annihilation of the Japanese carrier force by the Americans. On 5 June Admiral Yamamoto ordered the Japanese ships to abandon the operation and retire, the battleships reaching home waters again on 14 June. A month or two later, when US forces invaded Guadalcanal on 8 August, heavy Japanese reinforcements were ordered to the defence of the island. Yamato was sailed for the base at Truk on 11 August. She arrived on the 28th but in fact took no part in the subsequent bitter fighting in the confined waters off Guadalcanal, partly because of their confined and poorly charted nature, but also because there was no bombardment ammunition available for her 18in guns, and there was a general shortage of oil. She remained at Truk, being relieved as Fleet Flagship by her sister on 11 February 1943, until 8 May when she sailed for Kure, having been at sea only one day during the intervening period. Yamato arrived at Kure on 14 May 1943 and moved into the Inland Sea on 21 July. Her stay in home waters was not prolonged and after being assigned to the Battleship Force on 15 August, sailed the next day from Heigun Jima to return to Truk. After her arrival on 23 August she was incorporated into the Combined Fleet, Main Body, and re-assumed the role of Flagship, acting in command of operations at sea in which she herself played no part. But in October it was believed that a US assault on Wake Island was impending and the fleet sailed for Eniwetok on 17 October; it returned to Truk on the 26th without having made contact with the enemy. On 12 December 1943 Yamato left Truk for Yokosuka, covering Transport Operation BO-1, arriving at Yokosuka on the 17th. Her stay here was brief and after embarking stores for Truk she sailed again on 20 December, with orders to transport troop reinforcements to Kavieng and the Admiralty Islands. After sailing from Yokosuka for Truk, she was hit by a torpedo from the US submarine Skate on 25 December, which struck her on the starboard side aft, badly displacing the armour belt and exposing a significant defect in the protective scheme design. More than 3,000 tons of water flooded into the hull, but she managed to reach Truk safely. After unloading her cargo she effected makeshift repairs and then sailed for Kure on 10 January 1944, arriving on the 16th. During this passage, she was once more in contact with a US submarine and detached the destroyer Fujinami to attack it. After her arrival in Kure, the battleship was put into No. 4 dry dock for inspection. She was undocked on 18 March 1944, having completed repairs and some modifications including the landing of the beam 6.1in turrets. Post-refit trials began on 11 April and lasted about a week.
While in dockyard hands the ship had been assigned to the 2nd Battle Squadron. In mid April, following completion of work, she loaded stores and equipment for transport to the war zone and sailed once more on 21 April. Steaming via Manila, where the stores were disembarked, she reached Lingga Roads on 1 May. Here she was assigned to the Mobile Force and spent the first half of May in working-up before departing on the 11th for Tawa Tawa, the westernmost island of the Sulu Archipelago, where the fleet was presently based. She anchored there on the 14th to join the Mobile Force Vanguard for the A-Go Operation. On 10 June Yamato sailed with a force ordered to support the recently invaded island of Biak, but this operation was cancelled consequent upon the activities of US forces in the Marianas, and on 16 June Yamato joined the 1st Mobile Fleet to participate in the Battle of the Philippine Sea, 18-22 June, but this was essentially a carrier aircraft battle. By 24 June she was back in the Inland Sea where she remained until 8 July 1944. when, accompanied by her sister, she sailed for Singapore, arriving in Lingga Roads on the 16th, in preparation for the anticipated US attack on the Philippines. Yamato sailed with Force A to arrive at the Fleet base at Brunei Bay, Borneo, on 22 October, putting to sea again that night to intercept US operations off the Leyte Gulf bridgehead. On 24 October US carrier aircraft attacked the Japanese Force and Yamato was hit by two bombs and near-missed by another. The hits, forward, caused serious flooding, more than 3,000 tons of water entering her fore-ends. Next day, off the Island of Samar, Yamato and her consorts came into contact with US escort carriers and light forces and the battleship fired her main armament for the first and only time against surface targets. The action on her part was brief because of the tactical manoeuvrings. After this action had been discontinued, she suffered further air attacks and was hit again by bombs on 26 October. These attacks caused little major damage but did result in much flooding, and 33 casualties. Yamato retired to Kure for repairs, arriving on 11 November, after which she moved into the Inland Sea on 3 January 1945. There, on 19 March, she was hit again by a bomb during attacks by US TF58, while in Hiroshima Bay. That month it was resolved to deploy the battleship for what was essentially a suicide mission to support the defence of Okinawa where, having insufficient fuel for a return trip, she was to be beached as a stationary battery. The Special Surface Attack Force as it was known, consisting of the battleship, accompanied by the light cruiser Yahagi and eight destroyers, sailed from Tokuyama on 6 April bound for Okinawa. Next day, US carrier aircraft began their attacks and Yamato fired special AA shells from her 18in guns. Before she sank, the battleship is believed to have received hits from eleven, possibly thirteen, torpedoes and eight (confirmed) bombs in the space of a little more than an hour and a quarter. After a final huge explosion, she went down about 130nm WSW of Kagoshima. Yahagi and four of the destroyers were also lost.
Musashi commissioned in August 1942 and joined the 1st Battle Squadron attached to the Main Body, 1st Fleet. She remained in home waters like most of the other battleships, engaged on training duties and as a strategic reserve until 15 January 1943 when she was assigned to the Combined Fleet, Main Body, and sailed for Kure on the 18th, arriving at Truk on 22 January to relieve Yamato as Fleet Flagship, which she did on 11 February. After the death of Admiral Yamamoto in April, Musashi took his remains back to Japan for a state funeral, sailing from Truk on 17 May and arriving in Tokyo Bay on the 21st. In June she was stationed in the vicinity of Yokosuka and on the 24th received a visit from the Emperor before sailing for Kure and the Inland Sea next day. For the first eight days of July she was dry docked at Kure, after which she moved to the fleet anchorage at Hashira Jima. At the end of the month she moved to Kure in preparation for her return to the war zone and left on 30 July, bound for Truk where she arrived on 5 August. At Truk she resumed her role as Flagship and remained at anchor without putting to sea until 17 October when she sailed for Eniwetok. From here a strike was launched into the area of Wake Island 23-26 October, without result. Truk remained her base for some time thereafter until a US raid was suspected on the island, whereupon she was withdrawn to Palau early in February 1944 and subsequently ordered to Japan on the 10th, reaching Yokosuka on 15 February. Musashi sailed for Palau again on the 24th, loaded with stores and equipment. She lay at Palau as a unit of the 1st Mobile Fleet, Second Fleet, but was ordered back to Kure and sailed on 29 March. Shortly after leaving she was hit by one of three torpedoes fired from the US submarine Tunny. It struck the ship on the port side, at frame 27 about 6m below the waterline, causing considerable flooding forward and extensive hull damage. The destroyers Urakaze and Isokaze were detached to hunt the submarine, while the battleship limped on for Kure, where she arrived on 3 April 1944. On the 10th she was put into No. 4 dry dock for repairs and was undocked on the 27th. Musashi embarked various stores and equipment and sailed for Tawa Tawa on 11 May, where she arrived on the 16th to participate in the A-Go Operation. She was present at the Battle of the Philippine Sea but not in action and returned once more to Japanese waters, reaching the Inland Sea on 24 June. She remained in home waters until 8 July when she sailed for Singapore, anchoring in Lingga Roads on the 16th, and for the next few months was inactive until 18 October when she sailed with her sister as part of Force A to engage US forces off Leyte. Joining the rest of the fleet at Brunei Bay on the 22nd, the battleships continued into the Sibuyan Sea, where the Force was attacked by aircraft from US TF38.2, Intrepid and Cabot, on the 24th. During a period of about 4.5 hours Musashi bore the brunt of aircraft attack from eight US carriers. Hit by about twenty torpedoes and seventeen bombs, she capsized and sank early that evening.
Work on Shinano, not laid down until May 1940, proceeded only slowly, and when the initial experience of hostilities , i.e., the sinking of Prince of Wales and Repulse and the British attack on Taranto by carrier aircraft, indicated that the battleship might not now be the true capital ship, work was stopped in December 1941. In order to free the building dock, however, work was later continued at a low priority rate and, subsequent to the disaster of Midway in 1942, the decision was made to convert the ship to a carrier. Redesign work further delayed construction so that it was not until 1944 that she was floated out, but given that she was commissioned only shortly afterwards, Shinano must have been in an advanced state of completion at that time. Nevertheless she did required further work which was to be carried out after commissioning. She sailed from Yokosuka on 28 November 1944 for Kure where she was to embark her air group, despite her crew's lamentable state of training, the ship's very poor internal watertight integrity and the fact that many dockyard personnel were still at work aboard the ship. En route she was intercepted by the US submarine Archerfish off Cape Muroto, Shikoku, on 29 November and hit by four torpedoes. All four struck the starboard side and despite damage control measures, the inexperienced crew and poor watertight-ness combined to thwart all efforts and some seven hours later progressive flooding resulted in her capsizing and sinking.
When Japan attacked the USA the fourth ship was at a very early stage of construction, the hull being only some 30 per cent complete. Work was stopped in November 1941 and the order was cancelled in September 1942.