Yamato-class battleship

Yamato undergoing trials in 1941
Class overview
Name	Yamato class
Builders	Kure Naval Arsenal Yokosuka Naval Arsenal Mitsubishi Shipyard, Nagasaki
Operators	Imperial Japanese Navy
Preceded by	Nagato class (actual) Number 13 class (planned)
Succeeded by	A-150 class (planned)
Subclasses	2 (Shinano- and No. 797-class)
Cost	250,000,897 JPY
Built	1937–1942
In commission	1941–1945
Planned	5
Completed	3 (2 battleships, 1 converted to aircraft carrier)
Cancelled	2 (one subclass)
Lost	3
General characteristics (as built)
Type	Battleship
Displacement	69,988 long tons (71,111 t) (trials) 71,659 long tons (72,809 t) (full load).
Length	256 m (840 ft) (waterline) 263 m (862 ft 10 in) (o/a)
Beam	38.9 m (128 ft)
Draught	10.4 m (34 ft)
Installed power	12 water-tube boilers 150,000 shp (110 MW)
Propulsion	4 shafts; 4 steam turbines
Speed	27 knots (50 km/h; 31 mph)
Range	7,200 nmi (13,300 km; 8,300 mi) at 16 knots (30 km/h; 18 mph)
Complement	2,767
Armament	3 × 3-gun 46 cm (18.1 in) guns 4 × 3-gun 15.5 cm (6.1 in) guns 6 × twin 12.7 cm (5 in) guns 8 × triple 25 mm (1 in) AA guns 2 × twin 13.2 mm (0.52 in) machine guns
Armor	650 mm (26 in) on face of main turrets 410 mm (16 in) side armor (400 mm (16 in) planned on Shinano and No. 111), inclined 20 degrees 200 mm (8 in) armored deck (75%) 230 mm (9 in) armored deck (25%)
Aircraft carried	4 Aichi E13A, 3 Mitsubishi F1M 2 catapults (Yamato, Musashi) 47 aircraft (Shinano)

The Yamato-class battleships (大和型戦艦, Yamato-gata senkan) were two battleships of the Imperial Japanese Navy (IJN), Yamato and Musashi, laid down leading up to World War II and completed as designed. A third hull laid down in 1940 was converted to an aircraft carrier, Shinano, during construction.

Displacing nearly 72,000 long tons (73,000 t) at full load, the completed battleships were the heaviest ever constructed. The class carried the largest naval artillery ever fitted to a warship, nine 460-mm (18.1 in) naval guns, each capable of firing 1,460 kg (3,220 lb) shells over 42 km (26 mi).

Due to the threat of U.S. submarines and aircraft carriers, both Yamato and Musashi spent the majority of their careers in naval bases at Brunei, Truk, and Kure—deploying on several occasions in response to U.S. raids on Japanese bases.

All three ships were sunk by the U.S. Navy; Musashi while participating in the Battle of Leyte Gulf in October 1944, the Shinano while under way from Yokosuka to Kure for fitting out in November 1944, and the Yamato while en route from Japan to Okinawa as part of Operation Ten-Go in April 1945.

Background

The design of the Yamato-class battleships was shaped by expansionist movements within the Japanese government, Japanese industrial power, and the need for a fleet powerful enough to intimidate likely adversaries. Most importantly, the latter, in the form of the Kantai Kessen (“Decisive Battle Doctrine”), a naval strategy adopted by the Imperial Japanese Navy prior to the Second World War, in which the Japanese navy would win a war by fighting and winning a single, decisive naval action.

Musashi, August 1942, taken from the bow

After the end of the First World War, many navies—including those of the United States, the United Kingdom, and Imperial Japan—continued and expanded construction programs that had begun during the conflict. The enormous costs associated with these programs pressured their government leaders to begin a disarmament conference. On 8 July 1921, the United States' Secretary of State Charles Evans Hughes invited delegations from the other major maritime powers—France, Italy, Japan, and the United Kingdom—to come to Washington, D.C. and discuss a possible end to the naval arms race. The subsequent Washington Naval Conference resulted in the Washington Naval Treaty. Along with many other provisions, it limited all future battleships to a standard displacement of 35,000 long tons (35,562 t; 39,200 short tons) and a maximum gun caliber of 16 inches (406 mm). It also agreed that the five countries would not construct more capital ships for ten years and would not replace any ship that survived the treaty until it was at least twenty years old.

In the 1930s, the Japanese government began a shift towards ultranationalist militancy. This movement called for the expansion of the Japanese Empire to include much of the Pacific Ocean and Southeast Asia. The maintenance of such an empire—spanning 3,000 miles (4,800 km) from China to Midway Island—required a sizable fleet capable of sustained control of territory. Although all of Japan's battleships built prior to the Yamato class had been completed before 1921—as the Washington Treaty had prevented any more from being completed—all had been either reconstructed or significantly modernized, or both, in the 1930s. This modernization included, among other things, additional speed and firepower, which the Japanese intended to use to conquer and defend their aspired-to empire. When Japan withdrew from the League of Nations in 1934 over the Mukden Incident, it also renounced all treaty obligations, freeing it to build warships larger than those of the other major maritime powers.

Japan's intention to acquire resource-producing colonies in the Pacific and Southeast Asia would likely lead to confrontation with the United States, thus the U.S. became Japan's primary potential enemy. The U.S. possessed significantly greater industrial power than Japan, with 32.2% of worldwide industrial production compared to Japan's 3.5%. Furthermore, several leading members of the United States Congress had pledged "to outbuild Japan three to one in a naval race." Consequently, as Japanese industrial output could not compete with American industrial power, Japanese ship designers developed plans for new battleships individually superior to their counterparts in the United States Navy. Each of these battleships would be capable of engaging multiple enemy capital ships simultaneously, eliminating the need to expend as much industrial effort as the U.S. on battleship construction.

Design

The bridge of Musashi

The First Unoffical Designs for the Project (Hiraga's 1929 Design and "Design X")

Preliminary studies for a new class of battleships began (unofficially) before Japan's departure from the League of Nations and its renunciation of the Washington and London naval treaties. Before the project was officially requested as A-140 (Internal designation for Yamato), studies were already underway for a treaty tonnage replacement to the Kongō Class fast battleships (previously battlecruisers). This was the project in its original form and it was headed by Vice Admiral Yuzuru Hiraga in 1928/1929. His initial design had a tonnage of 30,000 long tons (30,000 t) and armed with nine 356 mm (14.0 in) guns in three triple mount turrets. The turrets had a similar turret design to Yamato which were mounted to a hull that was similar in design to modernized super dreadnoughts that Japan fielded extensively at the time (such as Kongō, Ise, Fusō and Nagato). Secondary Armament sources for this design remains sparse due to Japan destroying their design records at the end of the Second World War, but based on the drawings that were saved it was designed to be fitted with eight 140 mm (5.5 in) 55 caliber single mount casemate guns (two on each side, split between two groups fore and aft). Eight more of these guns in dual mount turrets on the fore and aft sides of the superstructure were also on this design. Finally it was to have four turrets in dual mounts of 127 mm (5.0 in) guns commonly found aboard the modernized Kongō, Ise, Fusō and Nagato; located near the front tower on all four corners. Neither armor protection, nor speed or powerplant is known, however it only had one s-shaped funnel amidships (similar to the Kii Class Design). The design was improved by this point and was presented to the Admiralty in July of 1929. This was known as Design-X (According to Breyer’s well known almanac book on battleships) which had a higher displacement of 35,000 long tons (36,000 t) and its main guns were wildly changed in arrangement and caliber. The Main battery called for two quad mount turrets, one furthest forward and one aft along with one 2 gun superfiring (behind the forward quad) turret of 410 mm (16.1 in) 50 caliber guns bringing the total amount of these guns to ten. The secondaries were designed, in both designs, so they could fill a dual purpose as AA cannons due to being designed to elevate 75 degrees. This design also substituted the 140 mm (5.5 in) 55 caliber guns found on the casemates and turrets on the old design with the 150 mm (5.9 in) 45 caliber guns used on many battleships of the time period and also used on multiple designs for Early 1920s Japanese Light Cruisers (Before the 155 mm (6.1 in) 50 caliber guns were in service). The exact Armor values of this design remain unknown, however it is known that it does have a double bottomed hull and a torpedo bulge. This design was so well liked by the Japanese Admiralty that even a wooden scale model was constructed. Although these designs were never attributed to the A-140 Project, they were the building blocks upon which further designs in the A-140 project would take shape.

Hiraga's First Unrestricted Design and Fujimoto's Competition Design

Starting in September of 1929, Vice Admiral Hiraga designed a new battleship. It was the first unrestricted (not bound by the Washington or London treaty) battleship in Yamato's lineage before the A-140 project started. Making the big displacement jump to a staggering 62,000 long tons (63,000 t) tons. It was very similar in looks (for the hull and the majority of her superstructure) to Hiraga's earlier "Design X" Proposal, but both the main and secondary battery changed. The Entire Main battery was situated forward of the superstructure like the Nelson Class of British fame. 9 guns in three triple mount turrets of 410 mm (16.1 in) 50 caliber guns were planned. The guns were arranged with all of the barrels pointing forward like the Nelson Class, with Turret B superfiring over Turret A and Turret C being behind Turret B. The secondary Battery of this design called for 3 triple mount turrets of 200 mm (7.9 in) guns (The early type 8 inch guns found on Furutaka in single mounts prior to modernization) mounted directly aft of the superstructure in a scheme similar to late design Japanese cruisers like Tone. The first and second turrets pointed forward and the second turret was capable of firing over the first. The third turret was mounted with the gun barrel's direction towards the stern. Additionally there were 6 turrets in dual mounts of 127 mm (5.0 in) guns located on either side of her main funnel, and in all four corners of her main tower. Her protection is known to a degree in that her armor in the citadel, turrets and conning tower were designed to theoretically protect the ship against 450 mm (17.7 in) guns between 20-30km in general, while 25-35km is the goal around her machinery parts. Her speed was calculated at 32 knots with a powerplant capable of 200,000 SHP which was reported to be a hybrid diesel/steam turbine setup. This is where future head designer Rear Admiral Kikuo Fujimoto enters the picture. Fujimoto, a competitor to Hiraga, made a similar unrestricted design that used a more traditional 9 gun setup for the main battery, like what was found on the Yamato class as designed. Hiraga's design made the cut in terms of further exploration and research partially due to the multiple unarmored, outside the citadel, 140 mm (5.5 in) secondary guns mounted to Fujimoto's design; which would have been a fatal design flaw.

Hiei As a Test Bed and the First Unofficial Request by the Admiralty

While work was continuing on refining the design, the Fast Battleship Hiei of the Kongō class became a test bed to mount the tower structure layout and fire control systems of the Yamato Class in order to test them aboard an existing ship. As a result of the proven testing of Hiei's Yamato inspired hardware and Hiraga's Early Yamato Design, the Japanese Admiralty unofficially requested an 8-12 main gun battleship with 460 mm (18.1 in) guns, however due to security and secrecy purposes it was decided to refer to the 18.1 inch guns as the 41cm (410 mm (16.1 in)) special type. While work on the new designs commenced, the testing of multiple variants of 460 mm (18.1 in) guns (2 45 caliber and 2 50 caliber) along with one variant of 510 mm (20.1 in) gun (rumored to be 45 caliber) started in 1934.

The Unofficial Designs from Partners Fujimoto and Ezaki

At around the same time the first two designs of this new construction request, which used a Yamato-like Hull and Hiei forward superstructure, was designed instead by a joint design partnership between newly minted Vice Admiral Ezaki Iwakichi, and Rear Admiral Kikuo Fujimoto (of which Ezaki was Fujimoto's Student in ship design). Fujimoto used his political and Admiralty connections to keep Vice Admiral Hiraga in the dark and out of the loop. This caused the project to succumb to lobbying from the Admiralty in the early years and produce unrealistic designs that would not be practical to be built. With this in mind, the two designs were 67,000 long tons (68,000 t) and 50,000 long tons (51,000 t) respectively. Each design had nine 460 mm (18.1 in) guns in a Nelson Style (50K ton design) or Mogami Style (67K ton design) Arrangement; similar to Hiraga's unrestricted 1929 design, however the secondary battery was altered to four 155 mm (6.1 in) triple mount gun, aft of the main superstructure which was of the late-type 6" guns mounted to Japanese light cruisers (one of which was in an extended tall barbette aft of the funnel and could fire over the other three). Additionally four dual mount 127 mm (5.0 in) guns were also planned to be fitted; with three behind the main tower (one of which was higher and could fire above the other two) and one mounted in a tall barbette (taller than the barbette of the second B turret) forward of the superstructure and behind C turret (the aftmost main turret). The larger design used a 6 shaft all diesel powerplant which was estimated to be capable of 31-33 knots. Additionally its armor design goal was to block 460 mm (18.1 in) shells between 20-35km. The 50,000 ton design was more practical with a four shaft diesel powerplant capable of 28 knots, but kept the armor of the larger 67,000 ton design.

Fujimoto and Ezaki's Disgrace and Their Removal from the Project

Unfortunately for Rear Admiral Fujimoto, the capsizing of the Torpedo Boat Tomozuru caused Fujimoto to be pulled off the project. He was initially relieved of duty, but when he was called back after the investigation by the admiralty concluded in January 1935 he tragically died the day after he was told to come back to the design department. The Fourth Fleet Incident in October 1935 also disgraced the second member of the design duo, Vice Admiral Ezaki, and as a result Ezaki was also dismissed from the project and initially relieved of duty. It was only due to his connections with the Admiralty staff that allowed him to stay in the design department, though his new job was calculating armor and hull strength and never was allowed to do any further warship designs himself. Vice Admiral Hiraga was also investigated as a result of the Tomozuru Incident and later Fourth Fleet Incident, but was later vindicated of any wrongdoing.

A New Chief Designer for the Project and the Last Design Before Withdrawing from the Treaties

Rear Admiral Keiji Fukuda was called to head the project, after Fujimoto's disgrace (and later Ezaki's), being made a Trustee of Vice Admiral Hiraga. Hiraga was then made temporary advisor to the project and therefore, thanks to his connections to the Navy Minister and the Chief of Staff of the Admiralty, he gained almost full control on the project. These factors combined with the distrust of the admiralty with the design department after the Fourth Fleet Incident of 1935 made it very easy for Hiraga to finally bring his designs to fruition. The first of these designs was drafted in August 1934; the last design drafted before the withdrawal of Japan from the Washington Treaty and official start of the A-140 Project. Displacing 55,000 tons and retaining the 9 triple turret 460 mm (18.1 in) 50 caliber guns in a Nelson-style Arrangement forward of the main superstructure; it was very similar to the previous designs including the armor design goal of blocking 18.1 inch shells between 20-35km. The differences include the speed increasing to 30 knots, and her secondary battery a decision between 12 155 mm (6.1 in) guns in 4 triple mount turrets or eight 203 mm (8.0 in) guns in 4 dual mount turrets. The 127 mm (5.0 in) armament from the earlier designs were the same, four dual mounts, but were located around the secondary tower in all four sides. The AA battery was finally realized with 8 triple mount 25 mm (1.0 in) guns similar to the ones seen in the 1945 Modernization of Yamato.

Design A-140 "Yamato" Project is Given Official Sanction (A-140A, B, C, D, A1, B1, C1, D1, A2 and B2)

By October 1934 a formal requirement was drawn up, after withdrawing from the Washington Treaty that same month (Later withdrawing also from the London Treaty), based on the Fukuda 1934 design's main specifications; with the added condition that the vessel could also mount 510 mm (20.1 in) later on. The design was called (internally) the designation A-140 for the first time as Fukuda started work on his first draft which was a refinement of the 1934 preliminary design which met the requirements of the admiralty perfectly. Although this design draft was completed in March 1935, there was still more designs to be considered and by April of 1935 he had come up with eight variants (A-140A, B, C, D and A1, B1, C1 and D1 respectively) for the upcoming meeting. A-140A was a steam turbine/diesel engine hybrid design capable of 30 knots and displacing 68,000 long tons (69,000 t) tons while the A140B was all diesel power, displacing 60,000 long tons (61,000 t) tons. Variants C and D were attempts to cut the size and displacement down to 58,000 long tons (59,000 t) and 50,000 long tons (51,000 t) tons respectively by reducing machinery spaces and the main gun size to 410 mm (16.1 in) guns. Even though the Admiralty liked the Nelson gun Arrangement, for ease of converting them to 510 mm (20.1 in) guns later, The A1, B1, C1 and D1 variants proposed by Fukuda used the two superfiring forward with one aft design of triple 460 mm (18.1 in) guns ubiquitous of the Yamato Class using the A and B variant’s powerplant and speed estimations. C1 and D1 again were supposed to be reduced displacement variants. The secondary guns were altered in these versions, using exclusively the late-type 155 mm (6.1 in) triple (12 guns in 4 triple turrets) from Japanese light cruisers. The 127 mm (5.0 in) armament was increased to 7 dual mount turrets while the 25 mm (1.0 in) guns were removed. This lead to two gun per turret variants proposed by Hiraga considered with A2 and B2 Carrying 8, 4 turrets with 2 guns each, 460 mm (18.1 in) guns, retaining the same powerplant and armor of the A and B variants discussed previously. The First Series A and B variants were chosen for further development.

The A-140 G Series (A-140G, G1-A, G0-A, G2-A and Three Unnamed Designs)

Three more designs were proposed between May and August of 1935 called the A-140G, G1-A, G0-A and G2-A which further promoted the forward arrangement much preferred by the Admiralty. Due to not liking the excess length and weight, the decision was made to reduce the length of the main battery’s barrels to 45 caliber along with narrowing the beam of the ship which reduced displacement to 68,500 long tons (69,600 t) tons and when combined with her steam turbine/diesel hybrid engines, was capable of 28 knots in the design specifications. Only one 127 mm (5.0 in) dual mount turret was removed from the design at this point which was positioned above the main battery near the bow. Instead the remaining six were repositioned to either side of the main funnel between the main and secondary towers, three per side. The G1-A variant reduced length even further, while making C turret reverse direction to be more in line with cruisers like Tone and Atago as it was believed that the guns would have better rear firing angles this way to defeat the disadvantages of having an all forward gun arrangement like the admiralty wanted. Deck armor was reduced to be able to block 18.1 inch guns at 27km instead of 30km which reduced the weight accordingly, however due to the cramped spaces for machinery from the draft, length and beam changes she was only capable of 26 knots. The G0-A further refined the previous, restoring the 28 knot top speed by lengthening the ship to previous levels while retaining the slimmer beam and draft to allow more room for machinery spaces. Additionally the design added four twin 25 mm (1.0 in) AA gun turrets around the main tower. Three more unnamed designs (though referred for reference as G1-B, G1-C and G1-D) were based on the G0-A before the G2-A design was finalized. These designs varied in speed between 26 and 27 knots, having split steam turbine/diesel powerplants and also having a unique main battery of 8 460 mm (18.1 in) 45 caliber guns. The foremost turret was in a twin mount turret, while the two behind having 3 guns per turret. The turrets were arranged in a Nelson-style Arrangement. The secondary battery also changed with the fourth 155 mm (6.1 in) turret being removed and repositioning two 127 mm (5.0 in) turrets fore and aft on extended tall barbettes. Ultimately the finalized design of this series was the G2-A going back to an Atago/Tone style arrangement of the turrets, a third gun back in the foremost turret (restoring the amount of main guns to 9 in triple mount turrets) and a restoration of the G0-A variant’s secondary battery specifications and the speed being back to 28 knots.

The Smallest Yamato Considered (A-140K, K1, K2 and K3)

The smallest design proposed as a further refinement to the G2-A was the A-140K which came with a length of 221 meters combined with only a 36m beam and 10.1m draught. The displacement for such a small vessel was still slightly over 50,000 long tons (51,000 t) tons. These variants sported similar changes as was in the three unnamed designs before the G2-A variant with the same main gun arrangement and also secondary 155 mm (6.1 in) battery, however the 6 127 mm (5.0 in) turrets of the G0-A/G2-A were retained. Three subsequent variants were proposed (designated K1, K2 and K3) which increased tonnage up to 54,000 long tons (55,000 t) tons, but the anemic 24 knot top speed (which even on subsequent variants couldn’t be corrected) due to very limited space for machinery meant the Admiralty rejected this design and all variants related.

A Yamato with 16 Inch Guns (A-140J0, J2, J3)

In July 1935 the next design in the evolution was the J-series starting with the A-140J0 which was a G2-A variant that had 410 mm (16.1 in) guns instead of 460 mm (18.1 in) and one less 155 mm (6.1 in) gun turret. It came out, displacement wise, at 52,000 long tons (53,000 t) tons and had a top speed of 27.5 knots. The competing J0 design rounded off the top speed to 28 knots and its designed armor was improved from the K series; able to absorb a 410 mm (16.1 in) gun between 18-27km. The J2 variant was next, which increased speed to 29 knots along with increasing operational range to 6000 nautical miles at 18 knots. The J3 was conceived and drafted at the end of August which would be very similar to that of the US Navy’s own Montana Class designs. It sported 12 410 mm (16.1 in) in 4 triple mount turrets (2 forward superfirinng and 2 aft superfiring). Secondary Battery is unaltered from the J2 except for 8 dual turret 25 mm (1.0 in) AA guns which were mounted four per side in two locations close together, a group of four at the main tower, and another group in the secondary tower. With a standard displacement of 58,400 tons, and with a speed of 28 knots it was good, but not great considering the sacrifice to armor. It was only rated for 410 mm (16.1 in) between 20 and 30km. As such the J series was never adopted.

The Final Design Takes Shape (A-140I)

The second to last design was A-140I which was completed near the end of August 1935. As main battery caliber and length discussions were still raging on Admiral Hiraga tried to convince the Admiralty about the merits of a traditional gun setup. This was culminated into the A-140I design which had a unique 10 gun 460 mm (18.1 in) setup with half of the four gun turrets aboard being twin gun turrets furthest forward and furthest aft and two more three gun turrets super firing behind the twin turrets and nearest the superstructure. A-140I’s Secondary Battery was altered with the two wing mounted 155 mm (6.1 in) triple gun turrets being removed and the remaining 2 being mounted fore and aft in tall superfiring barbettes behind the main battery, nearest the superstructure. Instead of 6 127 mm (5.0 in) dual gun turrets, 8 are now used; mounted on either side of the funnel, between the main and secondary towers. The armor was also capable of defeating 460 mm (18.1 in) guns between 20 and 27km. The displacement was now 65,000 long tons (66,000 t), much heavier, but still lighter than Yamato when she was completed in 1927. On paper the design was tempting, however there were issues with the requirement of two different types of turrets being manufactured for the same gun and the low weight efficiency of the arrangement was questionable, however it did offer better redundancy in case a turret was disabled than previous designs. This finally convinced the Admiralty to cave into a conventional Main Battery Layout.

The Final Design is Adopted For Further Revision (A-140F)

Rear Admiral Fukuda, in Late August 1935, at the same time as the development team was given the go-ahead to produce more traditional gun layout designs, produced the A-140F design. It differs from the Final Yamato design slightly because it has only 8 460 mm (18.1 in) guns in 3 turrets with two three gun turrets and one forward 2 gun turret. Additionally, in comparison to the A-140I the A-140F added an additional 2 triple 155 mm (6.1 in) guns in wing mounts to the side and removed 2 dual 127 mm (5.0 in) guns on either side of the central funnel. This design was selected by the Admiralty for production, provided that this design alone is refined further.

Improvements to the Initial Design (A-140F3, F4, F5 and F6)

As such, starting in October 1935, Turret one of the A-140F design became three guns instead of two, the hull form needed adjusting to accommodate the larger three gun turret on the bow and the turbine spaces were increased while the diesel spaces decreased due to lessons learned from the fact that Japanese marine diesel engines were less powerful and less reliable than initially thought. The diesel engines were removed from the design because of problems with the engines aboard the submarine tender Taigei. Their engines, which were similar to the ones that were going to be mounted in the new battleships, required a "major repair and maintenance effort" to keep them running due to a "fundamental design defect". In addition, if the engines failed entirely, the 200 mm (7.9 in) armored citadel deck roof that protected the proposed diesel engine rooms and attendant machinery spaces, would severely hamper any attempt to remove and replace them. Despite this, it retained 27 knots as a theoretical top speed. All of these changes, as well as the wing mounted 155 mm (6.1 in) guns were moved to amidships along with the 4 25 mm (1.0 in) guns mounted on the main and secondary tower in a similar fashion to previous designs. Armor was back to the standard; able to block 460 mm (18.1 in) shells from a distance of 20-30km. The problem with this A-140F3 design was the low operational range. This was improved with the F4 as more length was added for tank space to store fuel at the cost of a higher tonnage of 58,260 long tons (59,190 t). The F5 increased length to 253m and the Displacement Rose to 62,300 long tons (63,300 t). A-140F6 was the final design of the series and the production design on which Yamato and Musashi would be built in 1937 and beyond. As a result of concerns about the marine diesel engines, The F6 design reverted entirely from a Steam Turbine/Diesel hybrid to a Steam Turbine only setup at 64,400 long tons (65,400 t) displacement. The Yamato and Musashi were known as part of the 3rd Programme of this Development according to Fujimoto’s original 1934 Construction plans and started construction in 1937 with Yamato being the lead ship of her class.

Refits and Improved Variants

Musashi 1944 and Yamato 1945 Refit

The Yamato and Musashi were gradually improved with more AA guns and dual purpose secondary guns throughout the war; however a major refit was commenced near 1944/1945 for Musashi and Yamato. The refit for Yamato consisted of removing the wing mounted 155 mm (6.1 in) guns and replacing them for an additional six 127 mm (5.0 in) dual mount turrets on either side of the funnel, now 6 per side between the main and secondary tower along with up to 150 total 25mm Anti-Aircraft guns in triple mounts which were pretty much obsolete by the end of the war. Musashi kept her original gun arrangement of 6 127mm guns and had a modest amount of 25mm Anti-Aircraft guns in triple mounts added while her wing mounted 155mm (6.1 in) guns were also removed. It would have been likely, had Musashi survived to 1945, that she would have been improved after Yamato in the same manner.

Shinano and Warship No. 111 (Improved A-140F6)

A Later Improved A-140F6 Design variant which is called 4th programme by Fujimoto (who despite being dead and disgraced – did still have influence on the project’s development due to his plan being used by the design department) would incorporate lessons learned from Yamato and Musashi in time to be utilized on Shinano and Warship No. 111 (The third and fourth Yamato class hull). The design called for a triple bottom, as opposed to a double bottom on the Yamato, the Main Belt’s thickness was reduced by 10mm to 400mm, the Main deck’s flat portion by 10mm to 190mm and the main turret faces by 20mm to 540mm. Extra protection was proposed for the 155 mm (6.1 in) turrets in the form of 25mm added all round (~1 inch). The flag bridge and other flagship facilities would be extended along with an extended conning tower in the front, to improve functionality as fleet flagships. Fuel storage would be sacrificed a touch, due to over estimating how many fuel spaces were needed, to improve weight. Finally, the 12 127 mm (5.0 in) guns of the 1945 configuration of Musashi and Yamato would be replaced by 100 mm (3.9 in) 60 Caliber guns in dual turrets on a 1 to 1 basis. It is also speculated that these edits would also be made to Yamato and Musashi as a later refit.

Proposed Modifications (A Further Improved Shinano from the A-150 Project)

Fujimoto, in his plan for the Yamato class (which was still being followed in terms of construction) calculated that by 1942, the US Navy would surely know about the 18 inch main battery of the Yamato-class and would start building their own 18 inch armed battleships. To counter this, Fujimoto proposed that the existing Yamato Class, the 4th Program subclass (Shinano and Warship No. 111) and the new 5th Programme subclass (Warship No. 797 and 798) have their main battery increased to 510 mm (20.1 in) guns, which were tested and ready to begin production by the end of the war. The plan of this modification was finalized through the A-150 Project as the impracticality of the original design parameters of the A-150 project showed the limitations of Japanese Industry and drydock capacity that were not anticipated at its start. As such this further improved A-140F6 was a measure to still get 20.1 inch guns on a Japanese Battleship; however, it was slated to be mounted on the existing designs being built or already built instead of the new design originally talked about for the A-150 Project which originally had a displacement north of 85,000 tons. Although this plan was still never realized, due to the end of the war, the loss of Yamato and Musashi, the conversion of Shinano into an Aircraft Carrier and the cancellation of Warship No. 111; the plan called for a 1 to 1 replacement from Yamato’s to Warship No. 797 and 798 (the 5th and 6th Yamato Class hull) of her main battery with twin turrets of 510 mm (20.1 in) guns (6 total of these massive guns per ship for 6 ships assuming they all were afloat or under construction by that time). This Improved Yamato that was borne from the A-150 Project would be incorrectly referred to as the Super Yamato or otherwise the Main Design proposed for Project A-150, however the true A-150 Design was much more ambitious before it was decided to settle for upgrading the existing Yamato Class before the A-150 Project's eventual cancellation.

Approval

The designs were quickly approved by the Japanese naval high command, over the objections of naval aviators, who argued for the construction of aircraft carriers rather than battleships. In all, six Yamato-class battleships were planned by the time Yamato was built in 1937. Ultimately, only three were completed; one as an aircraft carrier, two as battleships. Other than the 1944/45 refits of Yamato and Musashi, there were no further edits or modifications to these ships that were completed or carried out before the two ships were both sunk. Shinano was converted into an aircraft carrier and later also sunk.

Ships

Yamato and Musashi anchored in the waters off of the Truk Islands in 1943

The Original FY1936 Construction Plan by Rear Admiral Fujimoto and Vice Admiral Ezaki in 1934 (during the unofficial construction project - prior to being designated A-140) called for an Incremental improvement in the Yamato design through 3 construction programmes of two ships each and four ships earmarked for future improvement projects based on Yamato (officially part of the 6th Programme). The first of these (3rd Programme) comprised Yamato and Musashi, with Shinano and Warship 111 being the second group (4th Programme) which were intended to be improvements over the original two ships. Another improvement was slated for Warships 797 and 798, of the 5th Programme followed by the four hulls of the later designated A-150 class of the 6th Programme. Although Fujimoto and Ezaki didn't head the project long during the Yamato class' development, their plan was used even after both of them were disgraced and Fujimoto died. In all, 10 hulls in this Plan were slated for the project, though after Fujimoto’s death and the construction of Yamato, four of these hulls were transferred to the A-150 Project which were under the 6th Programme.

Although six Yamato-class vessels had been planned by 1937 (Following the allocation of the remaining four hulls to the A-150 Project), only three —two battleships and a converted aircraft carrier— were completed. All three vessels were built in extreme secrecy, to prevent American intelligence officials from learning of their existence and specifications; indeed, the United States' Office of Naval Intelligence only became aware of Yamato and Musashi by name in late 1942. At this early time, their assumptions on the class's specifications were quite far off; while they were correct on their length, the class was given as having a beam of 110 ft (34 m)—in actuality, it was about 127 ft (39 m) and a displacement of 40,000–57,000 tons (actually, 69,000 tons). In addition, the main armament of Yamato class was given as nine 16 in (410 mm) guns as late as July 1945, four months after Yamato was sunk. Both Jane's Fighting Ships and the Western media also misreported the specifications of the ships. In September 1944, Jane's Fighting Ships listed the displacement of both Yamato and Musashi as 45,000 tons. Similarly, both the New York Times and the Associated Press reported that the two ships displaced 45,000 tons with a speed of 30 knots, and even after the sinking of Yamato in April 1945, The Times of London continued to give 45,000 tons as the ship's displacement. Nevertheless, the existence of the ships—and their supposed violation of naval treaties—heavily influenced American naval engineers in the design of the 60,500-ton Montana-class battleships, though they were not designed specifically to counter the Yamato class.

Construction data

Name	Namesake	Builder	Construction Program	Laid down	Launched	Commissioned	Fate
Yamato	Yamato Province (Great Harmony)	Kure Naval Arsenal	3rd Programme	4 November 1937	8 August 1940	16 December 1941	Sunk by aircraft during Operation Ten-Go, 7 April 1945
Musashi	Musashi Province	Mitsubishi Heavy Industries, Nagasaki	3rd Programme	29 March 1938	1 November 1940	5 August 1942	Sunk by aircraft during the Battle of the Sibuyan Sea, 24 October 1944
Shinano	Shinano Province	Yokosuka Naval Arsenal	4th Programme	4 May 1940	8 October 1944	19 November 1944	Initially Built as Battleship with improvements in secondary battery (12 100mm secondaries), removed 155mm/6.1 inch wing turrets, extended armor protection in flagship areas, conning tower and an extra inch of protection added to remaining two triple 155mm/6.1 inch guns. Lower main belt and main turret armor to compensate weight. Converted into aircraft carrier before she was finished as a battleship in July 1942. Torpedoed and sunk by USS Archerfish, 28 November 1944
Warship Number 111	—	Kure Naval Arsenal	4th Programme	7 November 1940	—	—	Planned to be built with the same improvements as Shinano. Cancelled March 1942 when 30% complete; Scrapped in place
Warship Number 797		Yokosuka Naval Arsenal	5th Programme	—			Planned to be built like Warship No. 111, but main battery later changed by A-150 Program to 6 20.1 inch or 510mm Main Guns in dual turrets. Slated for a 1942 Construction Program. Construction Cancelled before being laid down.
Warship Number 798		Kure Naval Arsenal	5th Programme				Planned to be built like Warship No. 111, but main battery later changed by A-150 Program to 6 20.1 inch or 510mm Main Guns in dual turrets. Slated for a 1942 Construction Program. Construction Cancelled before being laid down.
A-150 Hull #1		—	6th Programme				Initially Planned as Part of the Yamato Class. Later designated A-150 and made a separate class by 1937. Never Ordered. Rumored Hull No. 178.
A-150 Hull #2			6th Programme				Initially Planned as Part of the Yamato Class. Later designated A-150 and made a separate class by 1937. Never Ordered. Rumored Hull No. 179.
A-150 Hull #3			6th Programme				Initially Planned as Part of the Yamato Class. Later designated A-150 and made a separate class by 1937. Never Ordered.
A-150 Hull #4			6th Programme				Initially Planned as Part of the Yamato Class. Later designated A-150 and made a separate class by 1937. Never Ordered.

Yamato

Main article: Japanese battleship Yamato

Yamato on trials in 1941

Yamato was ordered in March 1937, laid down 4 November 1937, launched 8 August 1940, and commissioned 16 December 1941. She underwent training exercises until 27 May 1942, when the vessel was deemed "operable" by Admiral Isoroku Yamamoto. Joining the 1st Battleship Division, Yamato served as the flagship of the Japanese Combined Fleet during the Battle of Midway in June 1942, yet did not engage enemy forces during the battle. The next two years were spent intermittently between Truk and Kure naval bases, with her sister ship Musashi replacing Yamato as the flagship of the Combined Fleet. During this time period, Yamato, as part of the 1st Battleship Division, deployed on multiple occasions to counteract American carrier-raids on Japanese island bases. On 25 December 1943, she suffered major torpedo damage at the hands of USS Skate and was forced to return to Kure for repairs and structural upgrades.

In 1944—following extensive anti-aircraft and secondary battery upgrades—Yamato joined the Second Fleet in the Battle of the Philippine Sea, serving as an escort to a Japanese Carrier Division. In October 1944, as part of Vice-Admiral Takeo Kurita's Center Force for the Battle of Leyte Gulf, she used her naval artillery against an enemy vessel for the only time, helping sink the American escort carrier Gambier Bay and the destroyer Johnston before she was forced away by torpedoes from Heermann, which put her out of combat. Lightly damaged at Kure in March 1945, the ship was then rearmed in preparation for operations. Yamato was deliberately expended in a suicide mission as part of Operation Ten-Go, sent to use her big guns to provide relief to Japanese forces engaged in the Battle of Okinawa. She never came close, sunk en-route on 7 April 1945 by 386 American carrier aircraft. After receiving 10 torpedo and 7 bomb hits she capsized, taking 2,498 of the 2,700 crew-members with her, including Vice-Admiral Seiichi Itō. The sinking of Yamato was seen as a major American victory, and Hanson W. Baldwin, the military editor of The New York Times, wrote that "the sinking of the new Japanese battleship Yamato ... is striking proof—if any were needed—of the fatal weakness of Japan in the air and at sea".

Musashi

Main article: Japanese battleship Musashi

Musashi departing Brunei in October 1944

Musashi was ordered in March 1937, laid down 29 March 1938, launched 1 November 1940, and commissioned 5 August 1942. From September to December 1942, she was involved in surface and air-combat training exercises at Hashirajima. On 11 February 1943, Musashi relieved her sister ship Yamato as the flagship of the Combined Fleet. Until July 1944, Musashi shifted between the naval bases of Truk, Yokosuka, Brunei, and Kure. On 29 March 1944, she sustained moderate damage near the bow from one torpedo fired by the American submarine Tunny. After repairs and refitting throughout April 1944, Musashi joined the 1st Battleship Division in Okinawa.

In June 1944, as part of the Second Fleet, the ship escorted Japanese aircraft carriers during the Battle of the Philippine Sea. In October 1944, she left Brunei as part of Admiral Takeo Kurita's Center Force during the Battle of Leyte Gulf. Musashi was sunk 24 October during the Battle of the Sibuyan Sea, taking 17 bomb and 19 torpedo hits, with the loss of 1,023 of her 2,399-man crew.

Shinano

Main article: Japanese aircraft carrier Shinano

Shinano in November 1944

Shinano, originally Warship Number 110, was laid down as the third member of the Yamato class, albeit with a slightly modified design. Most of the original armor values were slightly reduced, including the belt, deck, and turrets. The savings in weight this entailed meant that improvements could be made in other areas, including added protection for fire-control and lookout positions. In addition, the 12.7 cm (5.0 in) secondary armament (in particular the amount on the 1945 Refit of Yamato) on the first two Yamatos was to have been replaced by the 10 cm (3.9 in)/65 caliber Type 98 gun. Although smaller, this gun was superior to the 127 mm, possessing a significantly greater muzzle velocity, maximum range, anti-aircraft ceiling, and rate of fire. The two 155 mm (6.1 in) wing turrets were also later removed in this design in reference to the refits that were made to Musashi and Yamato in 1944/45. This came from the Warship 797/798 variant design that were intended to exchange them for additional 100mm guns.

In June 1942, following the Japanese defeat at Midway, construction of Shinano was suspended, and the hull was gradually rebuilt as an aircraft carrier. She was designed as a 64,800-ton support vessel that would be capable of ferrying, repairing and replenishing the air fleets of other carriers. Although she was originally scheduled for commissioning in early 1945, the construction of the ship was accelerated after the Battle of the Philippine Sea; this resulted in Shinano being launched on 5 October 1944 and commissioned a little more than a month later on 19 November. Shinano departed Yokosuka for Kure nine days later. In the early morning on 29 November, Shinano was hit by four torpedoes from USS Archerfish. Although the damage seemed manageable, poor flooding control caused the vessel to list to starboard. Shortly before midday, she capsized and sank, taking 1,435 of her 2,400-man crew with her. To this day, Shinano is the largest naval vessel to have been sunk by a submarine.

Warship Number 111

Warship Number 111, never named, was planned as the fourth member of the Yamato class and the second ship to incorporate the improvements of Shinano. The ship's keel was laid after Yamato's launch in August 1940 and construction continued until December 1941, when the Japanese began to question their ambitious capital ship building program—with the coming of war, the resources essential in constructing the ship would become much harder to obtain. As a result, the hull of the fourth vessel, only about 30% complete, was taken apart and scrapped in 1942; materials from this were used in the conversions of Ise and Hyūga to hybrid battleship/aircraft carriers.

Warship Numbers 797 and 798

The fifth and sixth vessel, Warships Number 797 and 798, were initially planned as an improvement to the Shinano variant design with 460mm (18.1 in) guns, however these two planned hulls were repurposed by the A-150 Project to be an improved Shinano with 510mm (20.1 in) guns in 3 dual gun turrets and possibly increase the main belt armor to 18 inches after the initial designs of A-150 were rejected due to impracticality. This was the first purpose built design to do away with the two 155 mm (6.1 in) wing turrets in favor of additional 100 mm guns; authors William Garzke and Robert Dulin estimate that this would have allowed for up to 24 of these weapons. Yamato was eventually modified in 1945 to have 12 dual turrets of 127mm guns, while Musashi kept 6 turrets of these guns in their late war refits while removing the wing turrets for additional 25mm anti-aircraft guns. The wing turret removals were also considered for Shinano and Warship No. 111, though since the hull was nearly complete on Shinano would most likely have resulted in a refit in the docks during final fitting out (had she been completed as a battleship) and Warship 111 being the first to implement the wing turret changes in exchange for extra 100mm guns (initially this was desired to be 12 like Yamato's 1945 Refit, but as Garzke and Dulin point out it could have easily been more). The two ships were planned to be built during a construction program proposed to start in 1942. These ships were cancelled in 1941, following a strategy change to construct aircraft carriers and cruisers instead of Battleships. The Japanese defeat at Midway in 1942 further strained the shortage of Aircraft carriers and thus more resources were pulled away from Battleship production, completely halting the Yamato Class Program. Any hulls in the process of being built that couldn't be converted into aircraft carriers, like Warship No. 111, were scrapped and the steel was re-used for other projects.

The Four A-150 Design Hulls

Initially, these hulls were included as part of the original construction plan for the Yamato Class Battleships in early 1934 drafts by the first official head of the A-140 (Yamato) project Rear Admiral Fujimoto along with his trusted co-designer; then newly minted Vice Admiral Ezaki. After Fujimoto's disgrace following the capsizing of the Torpedo Boat Tomozuru (which was his design based upon a shortened variant of the Fubuki class destroyers) in a storm in March 1934 it caused an internal investigation by the Admiralty that ultimately led to his initially being relieved of his post. Though he was called back after the investigation completed in January of 1935, due to the Admiralty being partially culpable because of their excessive demands for weaponry on a given hull size, Fujimoto still no longer headed the project and tragically died the day after being called back to the Design Department. By October 1935 the Fourth Fleet, which comprised of designs that Fujimoto and Ezaki both designed together, were damaged and came back with visible cracks on the hulls which also resulted in investigation. The Admiralty concluded that something truly was wrong with these ships and as a result Ezaki was also dismissed from the A-140 (Yamato) project. As a result, these ships were not talked about until the finalized A-140F6 design was used to construct Yamato in 1937 and the A-150 Project came into being in 1938/1939. At which time, these four hulls of the original plan were allocated for the A-150 Project. They never had a Warship hull number other than rumor (It was rumored the first two were designated Warship No. 178 and 179, but this is unconfirmed), nor were the hulls ordered at all as part of the A-150 Project.

Specifications

Armaments

Primary armament

Yamato's port-side anti-aircraft armament as depicted on the model of the ship at the 'Yamato Museum' in Kure

The Yamato-class battleships had primary armaments consisting of three 3-gun turrets mounting 46 cm/45 caliber Type 94 naval guns – the largest guns ever fitted to a warship, although they were officially designated as the 40 cm/45 caliber (15.9 in) Type 94 – each of which weighed 2,774 tonnes for the complete mount. Each gun was 21.13 m (69.3 ft) long and weighed 147.3 metric tons (145.0 long tons), and could fire 1,460 kg (3,220 lb) armor-piercing shells and 1,360 kg (3,000 lb) high explosive shells out to 42.0 km (26.1 mi) at a rate of 1½ to 2 shells per minute.

The main guns were also capable of firing 1,360 kg (3,000 lb) 3 Shiki tsûjôdan ("Common Type 3") anti-aircraft shells. A time fuze was used to set how far away the shells would explode (although they were commonly set to go off 1,000 m (1,100 yd) away). Upon detonation, each of these shells would release 900 incendiary-filled tubes in a 20° cone facing towards incoming aircraft; a bursting charge was then used to explode the shell itself to create more steel splinters, finally, the tubes would ignite. The tubes would burn for five seconds at about 3,000 °C (5,430 °F) and would start a flame that was around 5 m (16 ft) long. Even though they comprised 40% of the total main ammunition load by 1944, 3 Shiki tsûjôdan were rarely used in combat against enemy aircraft due to the severe damage the firing of these shells inflicted on the barrels of the main guns; indeed, one of the shells may have exploded early and disabled one of Musashi's guns during the Battle of the Sibuyan Sea. The shells were intended to put up a barrage of flame that any aircraft attempting to attack would have to navigate through. However, U.S. pilots considered these shells to be more of a pyrotechnics display than a competent anti-aircraft weapon.

Musashi as she appeared in 1942; compare to the 1944 and 1945 configurations of the class, which removed the amidship 15.5 cm turrets to make way for additional anti-aircraft guns of 12.7 cm/40 Type 89 and 25 mm Type 96 varieties

Musashi as she appeared in mid-1944

Secondary armament

Yamato as she appeared c. 1945 (specific configuration from 7 April 1945)

In the original design, the Yamato class' secondary armament comprised twelve 15.5 cm/60 Type 3 guns mounted in four 3-gun turrets (one forward, two amidships, one aft), and twelve 12.7 cm/40 Type 89 guns in six double turrets (three on each side amidships). These had become available once the Mogami-class cruisers were rearmed with 20.3 cm (8.0 in) guns. With a 55.87 kg (123.2 lb) AP shell, the guns had a maximum range of 27,400 metres (30,000 yd) at an elevation of 45 degrees. Their rate of fire was five rounds per minute. The two midships turrets were removed in 1944 in favor of additional 127 mm (5.0 in) heavy and 25 mm (0.98 in) light anti-aircraft guns.

Initially, heavy anti-aircraft defence was provided by a dozen 40-caliber 127-mm Type 89 dual-purpose guns in six double turrets, three on each side of the superstructure. In 1944, the two amidship 15.5 cm turrets were removed to make room for three additional 127-mm mounts on each side of Yamato, bringing the total number of these guns to twenty-four . When firing at surface targets, the guns had a range of 14,700 m (16,100 yd); they had a maximum ceiling of 9,440 m (30,970 ft) at their maximum elevation of 90 degrees. Their maximum rate of fire was 14 rounds a minute; their sustained rate of fire was around eight rounds per minute.

Anti-aircraft armament

The Yamato class originally carried twenty-four 25 mm Type 96 anti-aircraft guns, primarily mounted amidships. In 1944, both Yamato and Musashi underwent significant anti-aircraft upgrades in preparation for operations in Leyte Gulf using the space freed up by the removal of both midships 15.5 cm (6.1 in) secondary battery turrets, and ended up with a complement of twenty-four 12.7 cm (5.0 in) guns, and one hundred and sixty-two 25 mm (0.98 in) antiaircraft guns, The 25 mm anti-aircraft guns could tilt at 90-degree angles to aim at planes directly overhead, but their mountings' lack of protection made their gunnery crews extremely vulnerable to direct enemy fire. These 25 mm (0.98 in) guns had an effective range of 1,500–3,000 m (1,600–3,300 yd), and an effective ceiling of 5,500 m (18,000 ft) at an elevation of +85 degrees. The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the fifteen-round magazines. This was the standard Japanese light AA gun during World War II; it suffered from severe design shortcomings that rendered it a largely ineffective weapon. According to historian Mark Stille, the twin and triple mounts "lacked sufficient speed in train or elevation; the gun sights were unable to handle fast targets; the gun exhibited excessive vibration; the magazine was too small, and ... the gun produced excessive muzzle blast".

The class was also provided with two twin mounts for the licence-built 13.2 mm Type 93 anti-aircraft machine guns, one on each side of the bridge. The maximum range of these guns was 6,500 m (7,100 yd), but the effective range against aircraft was only 1,000 m (1,100 yd). The cyclic rate was adjustable between 425 and 475 rounds per minute; the need to change 30-round magazines reduced the effective rate to 250 rounds per minute.

The armament on Shinano was quite different from that of her sister vessels due to her conversion. As the carrier was designed for a support role, significant anti-aircraft weaponry was installed on the vessel: sixteen 12.7 cm (5.0 in) guns, one hundred and twenty-five 25 mm (0.98 in) anti-aircraft guns, and three hundred and thirty-six 5 in (13 cm) anti-aircraft rocket launchers in twelve twenty-eight barrel turrets. None of these guns were ever used against an enemy vessel or aircraft.

Armor

Further information: Belt armor

Protection schematic at the rear turret; amidships schematic here

Designed to engage multiple enemy battleships simultaneously, the Yamatos were fitted with heavy armor plating described by naval historian Mark Stille as providing "an unparalleled degree of protection in surface combat". The main belt of armor along the side of the vessel was up to 410 mm (16 in) thick, with transverse bulkheads of the armoured citadel up to 355 mm (14.0 in) thick. A lower belt armor 200 millimetres (7.9 in) thick extending below the main belt was included in the ships as a response to gunnery experiments upon Tosa and the new Japanese Type 91 shell which could travel great lengths underwater. Furthermore, the top hull shape was very advanced, the peculiar sideways curving effectively maximizing armor protection and structural rigidity while optimizing weight. The armor on the main turrets surpassed even that of the main belt, with turret face plating 650 mm (26 in) thick. Armor plates in both the main belt and main turrets were made of Vickers Hardened steel, which was a face-hardened steel armor. Main armored deck—200 mm (7.9 in) thick—was composed of a nickel-chromium-molybdenum alloy. Ballistics tests at the proving ground at Kamegakubi demonstrated the deck alloy to be superior to the homogeneous Vickers plates by 10–15%. Additional plating was designed by manipulating the chromium and nickel composition of the alloy. Higher contents of nickel allowed the plate to be rolled and bent without developing fracture properties.

For torpedo protection, a multiple bulkhead side protection system was used which consisted of several void spaces as well as the lower belt armor; the system has a depth of 5.1 m (17 ft) and was designed to withstand a 400 kg (880 lb) TNT charge. No torpedo defense system compartments were liquid loaded, despite the known benefits. This may have been the result of overestimating the effectiveness of the lower belt armor against torpedoes, an effort to decrease draft, and provision of additional counter-flooding spaces.

The relatively new procedure of arc welding was used extensively throughout the ship, strengthening the durability of the armor plating. Through this technique, the lower-side belt armor was used to strengthen the hull structure of the entire vessel. In total, the vessels of the Yamato class contained 1,147 watertight compartments, of which 1,065 were beneath the armored deck. The ships were also designed with a very large amount of reserve buoyancy to mitigate the effects of flooding.

However, despite the immense armor thickness, the protection scheme of the Yamato class still suffered from several major design flaws and shortcomings. Structural weakness existed near the bow of the vessels, where the armor plating was generally thinner, as demonstrated by Musashi's damage from a torpedo hit in 1943. The hull of the Shinano was subject to even greater structural weakness, being hastily constructed near the end of the war and having been equipped with incomplete armor and unsealed watertight compartments at the time of her sinking. The torpedo defense system performed substantially worse than designed. In particular, very poor jointing between the upper-belt and lower-belt armor created a rupture-prone seam just below the waterline. When combined with the relatively shallow system depth and the lack of liquid loading this caused the class to be susceptible to torpedoes. Joint failures have been attributed to the considerable damage inflicted upon Yamato from a single torpedo impact in 1943, and to the sinking of Shinano from four hits in 1944.

Propulsion

The Yamato class was fitted with 12 Kampon boilers, which powered quadruple steam turbines, with an indicated horsepower of 147,948 (110,325 kW). These, in turn, drove four 6 m (20 ft) propellers. This powerplant enabled the Yamato class to achieve a top speed of 27 knots (50 km/h). With this speed, the Yamato class' ability to function alongside fast carriers was limited. In addition, the fuel consumption rate of both battleships was very high. As a result, neither battleship was used in combat during the Solomon Islands Campaign or the minor battles during the "island hopping" period of 1943 and early 1944. The propulsion system of Shinano was slightly improved, allowing the carrier to achieve a top speed of 28 kn (52 km/h).

"Super Yamato"-class battleships

Main article: Design A-150 battleship

Two battleships of an entirely new and larger design were planned as a part of the 1942 fleet replenishment program. Designated as Design A-150 and initially named Warship Number 178 and Warship Number 179, plans for the ships began soon after the design of the Yamato class was finished, probably in 1938–39. Everything was "essentially completed" sometime in 1941, but with war on the horizon, work on the battleships was halted to fill a need for additional warships, such as aircraft carriers and cruisers, to replace war losses of those vital ships. The Japanese loss in the Battle of Midway, where four carriers were sunk (out of ten, to date, in the entire navy), made it certain that work on the ships would never begin. In the third volume of their Battleships series, Axis and Neutral Battleships in World War II, the authors William H. Garzke and Robert O. Dulin asserted that these ships would have been the "most powerful battleships in history" because of their massive 51 cm (20 in) main battery and extensive anti-aircraft weaponry.

Similar to the fate of papers relating to the Yamato class, most papers and all plans relating to the class were destroyed to prevent capture at the end of the war. It is known that the final design of the ships would have had an even greater firepower and size than the Yamato class—a main battery of six 51 cm (20 in) guns in three turrets and secondary dual purpose armament consisting of twenty-four 10 cm (3.9 in) dual mounted guns (similar to the Akizuki-class destroyers). The displacement was to be bigger than the Yamato's, and a side armor belt of 46 cm (18 in) was planned.

Destruction of records

On the eve of the Allies' occupation of Japan, special-service officers of the Imperial Japanese Navy destroyed virtually all records, drawings, and photographs of or relating to the Yamato-class battleships, leaving only fragmentary records of the design characteristics and other technical matters. The destruction of these documents was so efficient that until 1948 the only known images of Yamato and Musashi were those taken by United States Navy aircraft involved in the attacks on the two battleships. Although some additional photographs and information, from documents that were not destroyed, have come to light over the years, the loss of the majority of written records for the class has made extensive research into the Yamato class somewhat difficult. Because of the lack of written records, information on the class largely came from interviews of Japanese officers following Japan's surrender.

However, in October 1942, based upon a special request from Adolf Hitler, German Admiral Paul Wenneker, attached to the German Naval Attache in Japan, was allowed to inspect a Yamato-class battleship while it was undergoing maintenance in a dockyard, at which time Admiral Wenneker cabled a detailed description of the warship to Berlin. On 22 August 1943, Erich Groner, a German naval historian, and author of the book Die Deutschen Kriegschiffe, 1815–1945, was shown the report while at the "Führer Headquarters", and was directed to make an "interpretation" and then prepare a "design sketch drawing" of the Japanese battleship. The material was preserved by Erich Groner's wife, Mrs. H. Groner, and submitted to publishers in the 1950s.

Cultural significance

The 1:10 scale model at the Yamato Museum

From the time of their construction until the present day, Yamato and Musashi have carried a notable presence in Japanese culture, Yamato in particular. Upon completion, the battleships represented the epitome of Imperial Japanese naval engineering. In addition, the two ships, due to their size, speed, and power, visibly embodied Japan's determination and readiness to defend its interests against the western powers, especially the United States. Shigeru Fukudome, chief of the Operations Section of the Imperial Japanese Navy General Staff, described the two ships as "symbols of naval power that provided to officers and men alike a profound sense of confidence in their navy."

Yamato, and especially the story of her sinking, has appeared often in Japanese popular culture, such as the anime Space Battleship Yamato and the 2005 film Yamato. The appearances in popular culture usually portray the ship's last mission as a brave, selfless, but futile, symbolic effort by the participating Japanese sailors to defend their homeland. One of the reasons that the warship may have such significance in Japanese culture is that the word "Yamato" was often used as a poetic name for Japan. Thus, the end of the battleship Yamato could serve as a metaphor for the end of the Japanese empire.

See also

• H-class battleship proposals (World War II German Kriegsmarine)
• Montana-class battleship (U. S. Navy)
• Yamato Museum
• Japanese munition ship Kashino Purpose-built ship to carry main gun turrets and barrels of the class

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• Wheeler, Keith (1980). War Under the Pacific. New York: Time-Life Books. ISBN 0-8094-3376-1.
• Willmott, HP (1999). The Second World War in the Far East. London: Cassell & Co. ISBN 0-3043-5247-0. OCLC 59378558.
• Yoshida, Mitsuru; Minear, Richard H. (1999) [1985]. Requiem for Battleship Yamato. Annapolis, Maryland: Naval Institute Press. ISBN 1-55750-544-6. OCLC 40542935.
• Yoshimura, Akira (2008). Battleship Musashi: The Making and Sinking of the World's Biggest Battleship. Tokyo: Kodansha International. ISBN 978-4-7700-2400-8. OCLC 43303944.

Further reading

• Dickson, W. David (1975). "I. J. N. Yamato". Warship International. XII (4): 294–318. ISSN 0043-0374.
• Lengerer, Hans; Ahlberg, Lars (2019). Battleship Tosa Demolition Tests to the modified Yamato Class. Capital Ships of the Imperial Japanese Navy, 1868–1945. Vol. 3. Zagreb: Despot Infinitus. ISBN 9789538218576.
• Thorne, Phil (March 2022). "Battle of the Sibuyan Sea". Warship International. LIX (1): 34–65. ISSN 0043-0374.

External links

• Kure Yamato Museum