The design of the Yamato class battleships grew out of Japanese resentment at the outcome the 1921 Washington Naval Treaty and the 1930 London Naval Treaty. These negotiations, in which Great Britain accepted parity with the United States, forced Japan to agree to a 5:5:3 ratio in capital ships – three for every five in the Royal and US Navies. When Japan invaded Manchuria, China in 1934, the League of Nations imposed sanctions upon Japan, at which point Japan dropped out of the League and abandoned all naval treaties. Already inferior in numbers, the Imperial Japanese Navy planned to redress the balance with ships more powerful than those of its rivals and likely enemies, so the designs for a new class of battleship that began at this point were unrestricted by any of the previous treaty limitations.
During the years 1934 to 1937 about twenty-four different designs were drawn up. Displacements ranged from 49,000 to 69,000 tons, speeds from 24 to 31 knots, various forms of a combined steam and diesel power plant were considered, and main gun calibres from 16in to 18in. Twin, triple and even quad mounts were proposed for the main armament, in different arrangements, including a layout similar to that of the British battleship Nelson. By late 1935 a design requirement of nine 18in guns in three triple turrets and a top speed of at least 27 knots had been established. The use of diesel engines was dropped from consideration, as the Japanese Navy was having trouble with some of their larger diesel power plants, and the complexity and cost of removing and replacing them in a capital ship would be too high. By early 1937 the final design of this new class of battleship was completely steam powered. The final design was approved in March 1937, but the first vessel, Yamato, could not be laid down until improvements to the yard facilities could be completed. The navy yards were well set up to construct battleships, but not on the scale of these new behemoths. The construction facilities had to be widened, lengthened and the approaches dredged deeper.
The Japanese wanted to keep the construction of this new class of warship a total secret, so there was a complete restriction on photography, as well as the construction of a roof over part of the building slip; there was even a gigantic curtain of rope used to block any view of construction and at Nagasaki a 400-ton camouflage net. These efforts to keep information from the Americans were generally successful, and by 1942, although the US Navy knew of the construction of at least two new battleships, they only had a rough sketch of the vessels. In fact, the US Navy’s Office of Naval Intelligence assumed that these vessels were armed with 16in guns and displaced 45,000 tons, and did not know the size of the main guns and the actual displacement of the battleships until after the war.
After the extensive modification to the Kure, Nagasaki, Yokosuka and even the Sasebo naval shipyards, which also included heavy lift equipment for the construction of these massive warships, Yamato’s keel was laid down in the dry dock at the Kure Navy Yard on 4 November 1937.
Prior to this, extensive research was conducted in hull model tank testing to develop the most efficient hull form possible. It was found that the large bulbous bow reduced hull resistance by over 8 per cent, as well as increasing buoyancy forward in heavy seas. It was also discovered that careful streamlining of the propeller shafts and the bilge keel added at least half a knot at full speed. Because of this research Yamato was able to achieve her maximum speed of 27.5 knots and an efficient cruising speed of 16 to 18 knots with only 150,000shp on a vessel displacing over 70,000 tons. Because of the extreme breadth of the hull, Yamato’s draught was only four feet more than other battleships in the Japanese Navy that displaced 30,000 to 40,000 tons less.
Other innovations incorporated in the construction of these warships included the methods of hull plating, using a mixture of lap- and butt-jointed plates. The smoother butt-jointed plating was used fore and aft to reduce frictional resistance in those higher water pressure areas, while the stronger lap-jointed method was used over the central portion of the hull. Extensive use of electric welding, new to shipbuilding at that time, was also made, although more of this assembly technique was used in the construction of the superstructure than in the hull.
Another innovation in the construction of the Yamato was the use of the armour plating as part of the actual hull structure, as opposed to an add-on. This made the armour an integral part of the hull, thereby increasing the strength of the hull as well as reducing the weight of its construction. The weight of Yamato’s armour was the heaviest of any warship ever built, and the ship was divided into the most watertight compartments (1147) of any battleship in history. These features made this class by far the most difficult battleships to sink by bombs and/or torpedoes.
The Musashi’s keel was laid down on the slipway at the Mitsubishi Industries Dock Yard in Nagasaki on 29 March 1938. Later, from May to November of 1939, the boilers, reduction gear and steam turbines were installed into the hull of Yamato. Although the Musashi was laid down five months later than Yamato, her construction was progressing at a faster rate, so that Musashi’s propulsion machinery was installed at approximately the same time as Yamato’s.
In July of 1939 the Mitsubishi Dock Yard also began the construction of a 10,000-ton freighter, the Kashino, which was purpose-built for transporting the massive 18.1in main gun barrels and the associated turrets. These were constructed at the Kure Arsenal and had to be transported by this ship to Nagasaki for installation aboard Musashi. For this role the hull form was unique and unusually broad for a freighter of this size, in order to accommodate the huge barbette and main gun turret assemblies. Kashino was completed in July 1940, after a couple of grounding accidents during her trials delayed her commissioning. This in turn delayed the construction of the Musashi by at least two months. The freighter was then used to transport further mountings to Yokosuka for the third Yamato class battleship.
The keel of this ship was laid down on 4 May 1940 in the dry dock at the Yokosuka Navy Yard. At this time the third member of the Yamato class was not yet named and was known simply as ‘Warship No 110’. She was to be built to a design slightly modified from that of the Yamato and Musashi, with slightly thinner armour, designed to withstand hits from 16in shells, as opposed to 18in shell protection of her sister-ships. Her beam was three feet narrower in an effort to increase her speed and she was to be fitted with the then new 3.9in twin mount AA weapon, as opposed to the 5in twin AA mounts fitted on the Yamato and Musashi.
In an effort to preserve the secrecy surrounding these warships, the mighty Yamato was ‘launched’ with little fanfare (actually floated out of the dry dock at the Kure Navy Yard) on 8 August 1940. Construction of her superstructure began at this point, as did the laying of her wooden decks. For these decks Japanese ‘Hinoki’ cypress was used, a relatively new timber first fitted to the Imperial Japanese Navy flagship Nagato. This wood was laid in smaller 5in widths, compared with the customary 7in wide teak planking fitted on all previous Japanese battleships.
The Musashi was launched on 1 November 1940, setting a record weight for a conventional slipway of 35,737 tons. The fourth and final Yamato class battleship had its keel laid down on 7 November 1940 in the same dry dock in which the Yamato had been built at the Kure Navy Yard. At that time this vessel was known as ‘Warship No 111’, and was to be a duplicate of No 110, a modified Yamato class.
Work was progressing at a steady rate on both the Yamato and the Musashi throughout early 1941. The gigantic size of these two warships was becoming apparent as the superstructures took form. The construction of the main gun turrets had actually started as far back as early 1940, but their complexity meant that they were not ready much before the point of completion of the entire vessel. Yamato had her main gun barrels installed during the months of May to July 1941.
In early October 1941 the Kashino transported the first of the massive 18.1in gun barrels for the second of the class, and thereafter would make regular trips from the Kure Naval Ordnance Arsenal to the Mitsubishi Industries Dock Yard to transport the turret components and the rest of the main gun barrels for the Musashi.
By late October, Yamato was running her trials in the Inland Sea, which went on into November. Numerous short voyages out to the Inland Sea were needed to calibrate and work up all equipment, including weapons, machinery, rangefinders, and many other aspects of this completely new weapons platform. Her final fitting out and adjustments after trials continued into December 1941.
The nine 460mm (18.1in) 45-calibre guns were the heaviest ever used afloat. The triple turrets each weighed 2516 tonnes (2774 tons). Barrel length was 21.13m (69ft 4in), they weighed 162 tonnes (178.6 tons) and had a range of 44km (27.3 miles) at an elevation of 45 degrees. The HE shells weighed 1460kg (3219lb). The secondary armament was 12 155mm (6.1in) guns mounted in four triple turrets and 12 127mm (5in) guns in twin mounts. Building was done on the raft body principle, with the vital areas contained within side armour of 410mm (16in) thickness, tapering towards the bottom to 75mm (2.9in), topped by a 200mm (7.8in) armoured deck and terminated by transverse bulkheads. Only the barbettes, flue gas uptakes and trunks for command systems, all heavily armoured, protruded through the ‘raft’.
Torpedo protection consisted of a bulkhead and a torpedo bulge with a maximum width of 3m (10ft), and to guard against explosions from below the side armour was continued as a floor 80–50mm (3.15–2in) thick beneath the magazines, with a space of around 4m (13ft 6in) to absorb explosive energy. Altogether there were 1065 watertight compartments below the armoured deck, and 82 above.
Instead of the ‘pagoda’ style superstructure of previous Japanese battleships there was a tall octagonal tower-mast, reaching 28m (92ft) above the waterline, with relatively few external features, though signalling wings were built out at bridge level. Control and chartrooms were arranged round a central armoured cylinder. A 15m (49ft) rangefinder surmounted the tower, with gunnery control centres above and below. The upper bridge extended forwards some 5m (16ft 4in), flanked by triple searchlights on each side.
The hull attained its maximum beam aft of the mid-point, part of the design scheme sometimes referred to as the ‘Kampon line’ and intended to minimise the stresses caused by the ship’s great length and the massive weight of the turrets. Despite its huge dimensions, Yamato was intended to be a fast ship, and at one stage diesel propulsion was proposed for the two outer shafts, with turbines for the inner ones. In the end an all-turbine drive was chosen, as in the original plan.
The surprise attack on the US Navy at Pearl Harbor by the Imperial Japanese Navy on 7 December 1941 not only caught the Americans off-guard but also the citizens of Japan and the yard workers constructing the Yamato class battleships. Yamato herself was commissioned on 16 December 1941 and became part of the First Battleship Division as third ship, with Nagato (flagship) and Mutsu. They would train together during the remainder of December and on into February 1942. On 12 February Yamato became the Flagship of the Combined Fleet, under the command of Admiral Yamamoto.
During this time work on the Musashi was pushed forward as quickly as possible, and the Mitsubishi Dock Yard assigned more workers to accelerate her construction. In the meantime the IJN was seriously reconsidering the construction of any more battleships. The successful attack upon the US Navy at Pearl Harbor and the sinking of the Royal Navy capital ships HMS Prince of Wales and Repulse dramatically emphasised the increasing potency of air power, and suggested a need for more aircraft carriers. In January 1942, work was ordered to be stopped on Warships No 110 and No 111, the modified Yamato class battleships, until the strategic direction of the IJN could be determined. By February, work resumed, but at a much reduced pace in an effort to finish the hull for No 110 in one year.
The Yamato remained in Japanese waters for the next few months, training her gun crews with particularly thorough drills, made necessary by the characteristics of the new monster 18.1in main armament. These weapons required a new approach to firing because their muzzle blast was so powerful it would shatter anything in its path. Crew members had to take complete cover, anti-aircraft gun mounts had to be covered with blast-proof shields, vents had to be faced away from the direction of discharge, and any optical devices had to be protected. Members of the future crew of her sister-ship Musashi were also aboard for this training.
On its first operational sortie Yamato, as the Imperial Japanese Navy Fleet Flagship, departed Japanese waters with a massive task force bound for Midway Island. The planned assault on that US Navy base was to be the next step in the Japanese advance across the Pacific Ocean, but in the ensuing Battle of Midway the US Navy won a decisive victory over the IJN in what turned out to be a massive duel between aircraft carriers alone. All four of the aircraft carriers in the IJN’s primary strike force were sunk, but the greater loss was that of the air crews from those carriers – a loss that the IJN was never to recover from. The Yamato was with the main invasion force, which turned back after the loss of the aircraft carrier force, and the entire operation was cancelled, with the fleet returning to Japan.
This battle changed the direction of planning within the Imperial Japanese Navy. There was a drastic and immediate need for more aircraft carriers after the traumatic losses at Midway, and it was at this time that the IJN made the decision to convert Warship No 110 to an aircraft carrier. The hull was about 50 per cent complete, with the propulsion machinery installed, which enabled the Yokosuka Navy Yard to make the conversion with less effort. The vessel was then given the name Shinano, but her completion as a carrier was never to be realized, as she was torpedoed by the USN submarine Archerfish on 29 November 1944 while being relocated to avoid destruction from American bombing of the Japanese home islands. At the time the ship’s fitting-out was far from complete, but she remained afloat for seven hours after four torpedo hits, barely assisted by the poorly organised efforts of an inexperienced crew, which must have been attributable to the basically sound underwater protection system. Also during the summer of 1942 the construction of Warship No 111 was halted and the 30 per cent complete hull was scrapped. Another battleship of a modified Yamato design (actually a modified No 110 design), known as Warship No 797, scheduled to start construction in the summer of 1942, was cancelled and was never laid down.
At this time the construction of the Musashi was delayed by at least three months due to the decision to fit her with flagship accommodation. In order to finish fitting her out and to run trials, she had been moved from Nagasaki to Kure. Musashi was commissioned into the IJN on 5 August 1942 and was assigned to Battleship Division One with Yamato, Nagato and Mutsu. However, Musashi remained at Kure for the next five months for additional fitting out and extensive trials and training of her crew in the Inland Sea. In September 1942 Musashi received the IJN Type 21 radar, with its massive antenna atop the main gun director arms. She also received four additional 25mm mounts on her main deck fore and aft of the wing triple 6in secondary turrets, both port and starboard. During this time, in August 1942, the Yamato sailed for the IJN forward base of Truk, in the Caroline Islands, about 1000 miles north of the Solomon Island chain. The Yamato was stationed at Truk with other IJN battleships of the Kongo class, who were very active during this time with the Guadalcanal campaign, but Yamato would remain idle for the next few months.
During the month of December 1942 Musashi exercised in the Inland Sea with the battleships Nagato, Yamashiro and Fuso. When she was finished with her training and post-trial refits, she was transferred to Truk, on 22 January 1943. Admiral Yamamoto then transferred his flag from the Yamato to the Musashi on 11 February 1943, but both battleships remained idle through April and into May 1943, even though the battleships Kongo and Haruna, also based at Truk, were still very active with the Guadalcanal campaign. On 18 April USAAF P-38 fighter aircraft, acting upon code breaking information, intercepted Admiral Yamamoto’s ‘Betty’ bomber transport aircraft and shot it and another down, killing the IJN fleet commander and most of his staff. By early May Admiral Koga had replaced Yamamoto as Fleet Commander of the Imperial Japanese Navy Combined Fleet. Musashi departed Truk bound for Yokosuka on 17 May 1943, eventually making a call at Tokyo, carrying the ashes of Admiral Yamamoto for his state funeral. Yamato had departed Truk one week prior to Musashi, bound for Kure Navy Yard.
In June of 1943, Musashi was cleaned up and prepared for an inspection tour by Navy Yard officials. The Japanese Emperor Hirohito visited the Musashi for a festive dinner and a tour of the entire battleship, including the crew’s quarters and the anti-aircraft defence position on the upper bridge. This was the one and only time the Japanese Emperor visited either one of his two super battleships.
During the month of July 1943 both Yamato and Musashi underwent a refit and upgrade at the Kure Navy Yard. Both battleships were dry-docked for hull cleaning and repainting, and the new paint job was extended to the entire superstructure and armament. Yamato received her first radar system, IJN Type 21, with its massive antenna atop the main director arms. Musashi was fitted with her second radar, the IJN Type 22, on both the port and starboard bridge top. Yamato received four additional 25mm AA mounts on her main deck fore and aft of the wing triple 6in turrets, both port and starboard. By the end of July 1943, with their refits and modifications complete, Musashi departed for Truk, followed by Yamato in mid-August.
On 18 September 1943 American forces attacked the Japanese-held island fortress of Tarawa with carrier-borne aircraft, in what was a prelude to the invasion of that island. In response to this the IJN Combined Fleet sortied from Truk for the Eniwetok atoll. This force included the battleships Yamato and Nagato, two fleet carriers, a light carrier, heavy and light cruisers and destroyers. Musashi, Fuso, Kongo and Haruna remained at Truk in reserve. The operation ended in anti-climax: after not making contact with the US fleet, Yamato and the IJN Fleet returned to Truk by the end of September.