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Japan's racehorses: The Owari-class battleships

1. The political setting
Japan and Koko started to prepare for replacing their oldest battleships as early as 1930. The Fuso-/Ise, Yagumo- and Kongo-classes could only be modernized to certain limits; only the Nagato- and Konishi-classes offered enough growth potential to play a role in long term planning. Preliminary designs were prepared, funds were set aside and resources were stockpiled. Politics delayed the start of the naval reconstruction programme till 1936; in this year, the Diet approved a four-year programme calling for the construction of four Type A battleships, four Type B battleships and four large fleet carriers. Priority was given to the Type A battleships and the carriers; the former became Yamato, Musashi, Shinano and Kii, the latter Shokaku, Zuikaku, Ryukaku and Taiho. One Type A battleship was laid down every year between 1937 and 1940; the carriers were laid down in pairs in 1937 and 1940/41. The Type B battleships were ordered in 1937 to be laid down two each in 1938 and 1939; actual dates were 1938, 1939, 1940 and 1941. The distinction between Type A and Type B battleships derives from Japan's operational planning for a Pacific war against the USA. Their strategy was to snatch the Philippines, Wake, Guam and Midway in a surprise attack first and fortify these islands, stationing submarines, airplanes and light craft there. Then they would wait for the USN to come and try take the islands back. On their approach, the USN would be harried and decimated by air, submarine and torpedo boat attacks. As soon as they passed the island chain, the IJN would strike: First in a massive night attack by masses of destroyers and cruisers, employing Japans supreme torpedoes to utmost effect, then on the following day, when the USN was cut down to a manageable size, by the main battlefleet around the Type A battleships, the three Nagatos and whatever new construction the Kokoans would contribute. Due to the crucial importance of the night attack, the cruisers and destroyers performing it were to receive a powerful backup by fast capital ships. This was the perceived role for the Type B battleship, whose speed was required to be high enough to operate together with Japan's extremely fast cruisers and which was to be able to overwhelm every enemy cruiser up to and including the four battlecruisers of the USN. The Japanese knew that the required speed of 33 knots could not be achieved on a balanced design, at least not if it was to be affordable (for a ship with USS Iowa's parameters, Japan's less advanced shipbuilding industry would have needed a 60.000 ton hull, whose price tag would limit numbers to an impractically small figure). Unlike the Type A Yamatos, which were designed without regard to price or such trivialities as treaty size limits and came out at 62.000 tons standard, the Type B battleships were limited to 35.000 tons (for reasons of cost and speed of construction, not to satisfy any treaty obligations). A second-rate armament of 356mm guns and protection only against their shells was accepted in order to secure a design speed of 33 knots. Being designed to perform a single role in a single battle, these most mission-specialized battleships of all time came out quite unbalanced and never got to fight the action they were designed for. Like all Japanese battleships, these four units were named for ancient Japanese provinces, recycling the names of unfinished ships of the 8-8 plan and ex-Russian prizes captured in the war of 1905: Owari, Iwami, Suwo and Tango. Although they were designed to conform to the WNT size limit, their construction was shrouded in the same secrecy as the Yamatos were.

2. Design and construction
As speed was the most important design parameter, the hulls of Design B-62a, which would become the Owari-class, were made slim and sleek; at 259m LOA and 31m beam, they had the highest length-beam ratio of any capital ship worldwide. The hull was carefully shaped to attain maximum hydrodynamic efficiency; like the Yamatos, they were equipped with protruding bow bulbs. They were fitted with four-shaft turbines of 180.000hp to attain the desired design speed of 33 knots. As usual when such extreme speeds were pursued, none of the class reached the design speed on trial displacement; the best figure was 32,79 knots, for which Iwami's engines had to be forced beyond 200.000 hp. This performance was still sufficient to place them among the fastest capital ships which were actually completed, together with the USN's Iowas and Alaskas. The hulls of the Owaris were flush-decked with a visible negative sheer aft, like Japanese heavy cruisers had. Protection was the bare-bones minimum that would allow them to engage enemy capital ships with 356mm guns. A 293mm external belt with 15° inclination was topped by a 114mm deck (140mm over magazines); general armour arrangement was similar to Yamato's, but with much thinner plates and without the armoured bottom beneath the magazines. The main armament was protected rather well with 360mm turret front plates and 330mm barbettes. Main armament consisted of nine fifty-caliber 356mm guns (officially designated 360mm because Japanese official designations always rounded gun calibers to the next full centimeter) firing 685kg shells at an elevation of 43° to a range of 40.000 meters. With their moderate muzzle velocity, these were very accurate and reliable guns with a RoF of 2 rounds per minute. Unlike the Yamatos, the Owaris eschewed a LA secondary battery and mounted sixteen fifty-caliber 127mm DP guns for use against air and surface targets. Eight triple 25mm mounts were included in the basic design. Due to their perceived role in the decisive night battle, they were given a powerful torpedo armament of sixteen 609mm tubes in four quad sets, each of them provided with four reload torpedoes in fast reload boxes; this was by far the most powerful torpedo battery ever installed on a battleship. The aviation installation resembled that of Japanese heavy cruisers with two parallel catapults placed amidships on a large aircraft handling platform, which spanned over the torpedo battery. Five scoutplanes could be carried, one on each catapult and three openly on the platform. The requirement to keep most of the amidships section free for airplanes and torpedoes necessitated placing the heavy and light flaks towards the ends of the citadel and into the blast zones of the heavy guns; although these guns produced much less blast pressure than Yamato's 406mm pieces, the flak mounts had to be provided with blast shields. Superstructure quite resembled Yamato's, but with a lower and more streamlined tower mast and a large gap for the aviation facilities between the raked single funnel and the straight pole mainmast and aft fire control stations. Despite their smaller size, the Owaris were technically sophisticated and needed nearly as long to be built as the Yamatos. Owari was laid down in June 1938 in the Yokosuka Navy Yard, launched in September 1940 and commissioned in July 1942. Iwami, not only the fastest of her class, but also the fastest to be built, was laid down in March 1939 at the Mitsubishi Yard in Nagasaki, launched in April 1941 and commissioned in February 1943 at Kure. Suwo was laid down in May 1940 at the Kawasaki Yard at Kobe, launched in June 1942 and completed in November 1944 at Maizuru. A July 1942 proposal to convert her to a carrier was ultimately rejected because she was too advanced to convert her in a timely fashion; eventually the first two hulls of the smaller, faster and less advanced B-65 super-heavy cruisers (Naniwa-class) were selected for a carrier conversion. Tango was laid down in August 1941 at the Kure Navy Yard and not very far advanced by the time of the defeat at Midway; when capital ship construction was severely curtailed in favour of aircraft carriers in the wake of this disaster, Tango belonged to the ships that were cancelled and broken up. As completed, Owari looked like this:

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3. Operations and modifications
Owari just missed the battle of Midway, where she would have done little good anyway. While several older capital ships were thrown into the fray at Guadalcanal, Owari stayed close to the remaining carriers, taking part in the battles of the Eastern Solomons and Santa Cruz without being damaged. During the Battle of Tassafaronga, Owari was at anchor at Rabaul. During January and February 1943, the Japanese/Kokoan fleet harried US forces evacuating Guadalcanal. Owari for the first time fired her main guns in anger when she sighted four retreating US transports, sinking two of them. During the battle of Espiritu Santo in April 1943, Owari was hit by two bombs from US aircraft and had to return to Japan; she was torpedoed by a Recherchean submarine on the return leg and eventually got lucky to make it home. She was relieved by her sister ship Iwami, which arrived just as the battle was raging. She had been completed with seven additional 25mm triples - bringing the total number to 45 - and two surface search radar sets, one on each side of the bridge tower. Like her sister before her, she stayed with the carrier force and made no contact with enemy forces during the conquest of New Caledonia. Iwami then took part in the offensive that culminated in the disastrous battle of Rotuma on August 17th, 1943 (described in detail in the post about the Kokoan Konishi-class). Iwami was accompanying the main battle force of Yamato, Nagato, Mutsu and the Kokoan Nagashiro and Suruga and fired several salvoes at the US battleship Indiana to little effect before the Americans abandoned the chase of the fleeing carrier force; she was not damaged in the action. During this battle, Iwami, which differed from Owari only by a slightly different arrangement of the W/T office behind the bridge, looked like this:

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After the battle, the Japanese were paralyzed for several weeks as Admiral Yamamoto struggled with his heavy wounds suffered in the battle of Rotuma and finally died. Owari rejoined the fleet in early September with the new light carriers Chiyoda and Chitose, replacing the damaged and recalled Kokoan ships. During the rest of 1943, the new Japanese C-in-C Admiral Koga kept his fleet at Rabaul, waiting for an US counterattack that would lead to a decisive battle. In November 1943, the IJN headquarters decided to send a strong raiding force into the Indian Ocean, after the Thiarian Navy had stopped their own raids in order to concentrate on supporting their faltering land campaign in Brazil. Owari and Iwami, being the fastest battleships available, were detached together with the heavy cruisers Tone and Chikuma and the light cruisers Yodo and Ishikari, commanded by Vice Admiral Sakonju. They reached Singapore in December 1943 and performed four sorties into the Indian Ocean between late December 1943 and March 1944. During the third of them, they engaged a convoy on the Trincomalee-Aden route, protected by considerable Recherchean forces including the old battleship HMRS Fearless. Outnumbered and outgunned, the Fearless nevertheless put up a valiant fight; she first sank the light cruiser Yodo, then inflicted considerable damage on Owari, before Iwami's fire overwhelmed her. The Japanese kept firing at her even as she was capsizing, and she was lost with all hands. Her convoy scattered, but six merchants were caught by Chikuma and Ishikari and torpedoed. During this raid, the Japanese made 383 British and Recherchean prisoners; as Sakonju was under orders not to burden himself with such, he had all the officers beheaded, the ratings shot and the civilians thrown overboard. Owari had to return to Japan after this engagement, but the other ships embarked on a fourth raid in March, which was called off when a Free French squadron around the battleship Richelieu was sighted, which Sakonju rightly deemed too strong for Iwami to mess with. When the Americans finally launched their counteroffensive against New Caledonia and the New Hebrides, Sakonju's force was recalled. They rejoined the Japanese main fleet in May 1944, but under Admiral Koga's leadership (or lack thereof) they failed to bring the Americans to battle as they swept the Solomons clear of Japanese forces in a series of excessively bloody amphibious assaults. Owari was repaired in June 1944, but was kept in Japan for several months together with the carrier Taiho in case the Americans launched another surprise strike against Koko like the one that had resulted in the disastrous second battle of Midway in May 1944. They were reinforced by Suwo, third unit of her class, and the new aircraft carriers Unryu and Naniwa in November 1944. Suwo, the last capital ship completed for the IJN, differed from the other two by lacking any torpedo armament; instead, she was fitted with a fifth pair of 127mm DP guns amidships without blast shields. The number of 25mm guns had been brought to 69 in 23 triple mounts. When she was commissioned on November 4th, 1944 at Maizuru, she looked like this:

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Suwo, Owari and the three carriers plus five cruisers under overall command of Admiral Kurita followed Koko's main fleet on its journey south and were 250 miles behind it when it ran into a powerful USN force in the battle of Truk in January 1945. Kurita repeatedly requested orders to assist the Kokoans, but was ignored by Admiral Toyoda till it was too late. When they rejoined Toyoda's main body in late January, all three Iwami-class ships for the first time operated together. Quarrels between Toyoda and the Kokoan commander Admiral Minasoko effectively paralyzed the axis fleet for weeks, but these weeks could at least be used to train the carrier pilots of both fleets a little better. Only light forces were sent to oppose the allies as they retook the Gilbert and Marshall Islands, and these were always wiped out. But when the US moved against Saipan in May 1945, Toyoda's fleet was as ready as the IJN and KnK had not been since before the first battle of Midway, especially as the new carriers Chihaya and Katsuragi reinforced it in April 1945. Owari, Iwami, Suwo, Hiei and the Kokoan Konishi and Kitamori, together with ten cruisers, formed the screen for the largest axis carrier fleet of the entire war, consisting of Shokaku, Zuikaku, Taiho, Chihaya, Naniwa, Unryu, Katsuragi and the Kokoan Haitaka, Inuwashi and Hachuko; another six small carriers covered the battle force of Yamato, Musashi, Shinano, Nagato, Kongo and the Kokoan Nagashiro, Nakamori and Suruga. Only the carrier forces pounded each other in the resulting battle of the Philippine Sea in June 1945, which was a clear tactical victory by points for Toyoda due to the availability of a new generation of carrier aircraft whose excellent performance thoroughly surprised the Americans. Unfortunately, although many US ships were damaged, only few could be sunk, and the overall correlation of forces shifted even more in favour of the Allies as two aircraft carriers (Unryu and Zuiho) and two cruisers from Toyodas fleet were sunk by US submarines in June and July 1945; the carrier Taiho was damaged. The US invasion of Saipan was delayed a mere six weeks; the Americans simply waited till the damaged Axis ships had been recalled for repairs, and Toyoda did not dare to attack them again with what remained. While the Allies built up the largest fleet ever concentrated for the attack on the Philippines, the Japanese and Kokoans frantically repaired their damaged ships and rushed every available reinforcement to the front. In late September, the US submarine arm struck again, and Suwo was severely damaged and returned to Japan, missing the Battle in the Leyte Gulf, where both her sisters met their fates. While Iwami had not changed her look since 1943 very much apart from receiving the compulsory additional 25mm guns (36 barrels in her case), Owari had been modernized at the Sasebo Arsenal during her stay in Japan late in 1944. She received a new radar suite including Thiarian supplied fire control radars for the main and DP guns and two additional 127mm twin mounts amidships as on Suwo. The number of 25mm guns was brought to 93 in 31 triple mounts. She landed her torpedo tubes and exchanged her floatplanes against new E16As. On the eve of the battle in the Leyte Gulf, Owari looked like this:

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Both sisters were assigned to different forces; Owari joined Kurita's center force, Iwami accompanied Ozawa's carriers. When Kurita charged Admiral Bogan's US carriers, Owari and Kongo, supported by Shinano and Musashi, managed to break past the allied escort force around USS Alabama and the Thiarian Athartha. Owari damaged the US battlecruiser USS Guam very heavily (she was later finished off by Shinano, becoming the only ever US capital ship to be sunk by a Yamato-class vessel), sank the heavy cruiser USS St.Paul and charged the US carriers which were just fending off a massive land-based torpedo attack. She then attacked USS Boxer, which had been damaged by two aerial torpedoes from land-based P1Y aircraft, and rendered her in a sinking condition with fifteen hits. Due to her three-knot speed advantage over Kongo, which tried to keep up with her, both ships were separated wide enough that Owari could not effectively interfere when Kongo was run down and sunk by the Thiarian battlecruiser Caithreim. Owarii's Skipper turned to assist Kongo, but by the time he had the enemy in range, Kongo was already gone. The US carriers escaped. Owari and Caithreim then had a lengthy long-range gunnery duel, with Caithreim enjoying the advantage due to her more modern fire control radar, her ability to jam Owari's older Thiarian-built radar at will, her slightly heavier shells and her much better horizontal protection. With his ship accumulating damage without hitting back effectively, Owari's skipper broke off the engagement and headed north, but was entirely cut off from Kurita's forces and eventually caught in a massive strike from Admiral McCain's US carriers. She was hit by six aerial torpedoes and ten bombs and immobilized, burning violently. Uncharacteristically for the IJN, her CO ordered her abandoned and scuttled, and over 1.500 of her 1.800 crew could be taken off and were rescued by US forces. While all this happened, Iwami was unable to prevent the near total annihilation of Ozawa's carriers despite shooting down 15 US airplanes. To add insult to injury, she was not even targeted by the Americans. When the battered remnants of Ozawa's fleet dispersed and fled, Halsey, who needed his planes to go after Kurita's center force, allowed his fastest capital ships to pursue. The Recherchean battleships Audacious and Dauntless specifically went after Iwami, bent on avenging the sinking of HRMS Fearless and subsequent prisoner massacre. Iwami was able to outrun them, leaving the Kokoan battlecruisers Konishi and Kitamori to fend off the pursuing allied forces all on their own, but Audacious and Dauntless kept following Iwami even as Konishi sank the large Recherchean cruiser Geographe. Their persistence paid off when Iwami literally ran afoul of the US submarine Corsair, which she rammed and sank. She however damaged her bow bulb in the process, suffering some flooding forward and cutting her speed to 25 knots. Now Audacious and Dauntless caught up and attacked. True to the spirit of Bushido, Iwami came about and returned fire. She hit Dauntless eleven times and considerably damaged her, but was herself hit over thirty times and suffered a cataclysmic explosion of her port torpedo battery. After this explosion, her guns were silenced, but the Rechercheans kept bombarding her till she capsized and went down with all hands, having suffered in excess of a hundred shell hits, some at a distance of under 3.000 meters.

After Leyte, only Suwo was left of her class. For three months, she was the only Japanese capital ship in home waters, then the battered remnants of Kurita's Center Force broke through from Singapore. During her repair and refit at Maizuru, which was complete in February 1946, she increased the number of 25mm guns to 102; her radar suite was upgraded with the same Thiarian fire control system as on Owari and she also received the latest Thiarian air search radar, which was confiscated on Koko during the uprising and brought to Japan. With Japan's oil supply ruptured, the remaining ships were all but immobilized, and Suwo received an elaborate camouflage paintjob of three different shades of green. When the Americans started to systematically bomb Japan's ports, Iwami got lucky when a barge moored next to her was blown apart by an aerial torpedo in April 1946. She did not participate in Yamato's and Shinano's final sortie towards Okinawa which literally used up the last drops of Japan's fuel oil in June 1946 and was still afloat when Japan eventually surrendered after the nuclear attacks on Hiroshima and Nagasaki, looking like this:

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She became an US prize and was transferred to the USA in December 1946. As the newest surviving Axis capital ship, she underwent a comprehensive test programme and was not used up in the 1947 nuke tests. During her trials programme, she performed a high speed run during which she reached 33 knots at 202.000hp and repeatedly fired her guns in full salvoes, all of this being extensively filmed; footage of her appeared in about fifty war movies until well into the 1980s. After the Americans had concluded the trials in 1948 and determined there really was nothing new they could learn from Suwo's design and construction, she was moored at Puget Sound till 1955, before she returned to her country of origin to be scrapped. A Japanese request to preserve her instead was categorically rejected by the Americans and she was broken up in 1956.

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GD

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