Koko Kyouwakoku (Republic of Koko)

This entry basically erases the two old entries of the Yagumo class, and other than a complete redesign of the ship also adds the WWII history that was previously missing.

Yagumo Class Battleship:

By the 1910s despite having built its mainline fleet to a considerable strength, Koko no Kaigun suffered from a premature obsolescence of her large combatants as a consequense of the all-big-gun concept initiated by HMS Dreadnought. Thus as early as of 1910 a first request for new naval construction was put forward to the Diet. The original request, calling for six new capital ships was ultimately cut down to two but eventually was approved by 1911.
Designs for Koko's first Dreadnought Battleship had already started in late 1907, ultimately producing the battlecruisers Aomegami and Kuromegami, but went on even after 1910: at first many concepts were taken into account, rangin from a super-Kawachi design with superfiring turrets, to a modified Kongou Class with Armor upgraded to battleship standards at the expense of speed, and to a simple carbon-copy of the Fuso Class Battleship. Ultimately, the Kawachi design was discarded because it was too dated, and the Kongou and Fuso ones because Toumachi Naval Arsenal would have needed to expand its slipways to build vessels of that size.
By early 1913 designers started to focus thier efforts on a smaller version of the Fuso Class. A shorter hull housing only five, instead of six, 356mm turrets with comparable armour protection and and higher top speed. The plan called for a 188,6m long ship (14 less than a Fuso) with a beam of 27,2m (1,5m less), a draft of 8,9m and an assumed displacement of 24.450t at standard load. the ten 356mm/45 guns would have been argumented by sixteen casemate 152mm/50 guns, six 76mm/40 A-guns and four 533mm torpedo tubes. Armor values were to be the same as the IJN fuso. Assumed top speed was expected to be at least 23,5 knots.
The two battleships were funded in July 1914, but the sudden outbreak of WWI and the repairs needed on Aomegami, who hit a German mine off Tsingtao in late October 1914, delayed the start of their construction. The lead ship, to be called Yagumo, was laid down in January 1915 at Toumachi Naval Arsenal. By that time, the design had been modified once already. Despite Aomegami sea trails had not been completely succesful (the ship failed to reach the planned top speed) the Naval staff decided to attempt pursuing speed on their new battleship class as well. The hull, while maintaining beam and draft unchanged, was lengthened to 201,2m overall (with waterline being 198,8. The same as the Kuromegami and the most available military shipyards could allow) The planned increased displacement to 26.176t was offet by the fitting of a completely new engine layout. Kampon boilers fueled by 68% of oil and 32% of coal powered Brown-Curtis steam turbines that were to generate at least 70.000 to 74.000 shp for a planned top speed well above 25knots.
This revised design also lasted a bit more than a year, the Battle of Jutland, the loss of Kuromegami against the Thiarians, and the modifications already implemented by the IJN to the third and fourth Fuso class units, that became the Ise class, led Koko designers retouch the plans for the Yagumo class once more despite the lead ship was already under construction. When launched, in 1917, and ultmately commissioned in december 1918 Battleship Yagumo bore little resemblance to the ship that was originally ordered four years before.
While overall dimensions had remained the same as the previous iteration, as it was for the 10 356mm guns making up for the main armament, mostly everything else had ben modified:
The planned sixteen casemate 152mm/50 guns were instead replaced by sixteen 140mm/50 ones, main belt was made of an uniform thickness of 305mm and an upper belt of 102mm protecting the casemate decks was added. An internal torpedo bulkhead 25mm thick was added and deck armor increased from 51 to 85mm. On trials, her engines easily generated 74.917shp that propelled the ship to a 26 knots top speed, making Yagumo the fastest capital ship at the time that was not a battlecruiser. Range totaled 8.800 nautical miles at 14knots. Yagumo displaced 26.981 at standard load and 31.508t full, her draft had increased to 9,1m over her planned 8,9. torpedo tubes were deleted during construction in order to balance the increase in weight caused by the extra armor and the new engines.
Upon commission Yagumo immediately replaced Aomegami as Koko no Kaigun's Flagship.
[ img ]

The second ship of the class, Inaba, was laid down at Toumachi Naval Arsenal in 1917, as soon as Yagumo was launched. Construction lasted until her launch in 1920, and she was commissioned in early 1921. Compared to her sister Yagumo, Inaba had the deck armor thickness further increased to 100mm, and she displaced 27.218t standard and 31.319t at full load, Her appearance was also different to address issues emrged during Yagumo's service. Larger flag platforms were added on the fore and aft supestructures, and a donkey boiler room added between the funnels. As smoke interference issues had been experienced on Yagumo, the foremast platforms and funnels were modified accordingly: a cap was added on the forward funnel, the searchlight platforms were extended forward. Enclosed lookout stations were added and the foremast was shortened. The spotting top was expanded. Both ships had a crew of 1.124 officers and men.
[ img ]

Inaba replaced Yagumo for Flagship roles during 1921, then both Battleships attended celebrations for the newly signed Kokoan-Japanese Alliance as part of the Bilateral agreements of 1921 and easily survived the Washington Naval Treaty. In september 1923 they departed for Japan to provide support and relief after the great Kanto earthquake had devastated Tokyo and Yokohama.
In late 1925 Inaba was docked at Hoshiguma Navy Yard for an upgrad of her fire control system. During the works, all the 6-meter rangefinders on the main guns were replaced with 8-m ones, and the maximum elevation increased from 25 to 33°. The aft bridge recieved a 2,8m rangefinder and a fire control platform was added on the tripod foremast, requiring the relocation of the 90 and 60cm searchlights. Finally the casemate guns recieved canvas bags.
[ img ]

Yagumo was supposed to recieve a similar modernization, but all the shipyards were full with new Destroyers construction, The newer Battlecruiser Amagi had just entered service in 1926 and after the Geneva conference in 1927 Koko was allowed to scrap the Goryo class battlecruisers to build newer Battleships. Yagumo's refit was thus postponed to 1930/31: therefore it was also planned to carry on a larger and much more comprehensive refit on her. But the ratification of the London Naval Treaty in October 1930 forced Koko no Kaigun to a change of plans.
Under the provisions set by the newly ratified London Naval Treaty, Yagumo's main refit was canceled. The ship was Drydocked at Toumachi Naval arsenal in January 1931 to be converted into a training ship, works going on until mid 1932. During conversion all her oil-fired boilers were removed, dropping engine power to 23.973shp (down from 74.917) and top speed to 18,5 knots (pre-refit was 26knots), the fore-funnel was thus removed. The forward superfiring and the midship 356mm (14-inch) turrets were removed, as they were ten of the sixteen 140mm (5.5-inch) casemate guns, half of the 76mm (3-inch) AA guns were removed as well. The main and upper side armor belt was also removed, one of the 76mm guns were moved on top the former midship 356mm gun barbette, and three twin mounts for the newer 127mm (5-inch) guns were added, two on the sides of the bridge and one on top of the former forward superfiring turret. All modifications decreased the ship standard displacement by 5.922t to 21.059t, decreasing draft from 9,1 to 7,2m. Other works consisted in adding covered spaces for cadets at midship and fitting training guns and new platforms and improved rangefinders for fire-control practices.
[ img ]

Shortly after her sister left the yards, Inaba was docked at Toumachi to uderwent her main modernization, the same one Yagumo would have underwent if not for the LNT; Inaba's stern was lenghtned by 7,6m, increasing length to 208,8m, and anti-torpedo bulges were added bringing the full beam to 31,4m, with both the fore and aft superstructure completely reconstructed in order to house newer and more advanced directors and fire-control equipment, all topped by an 8-m rangefinder fitted on the forward superstructure. All 76mm guns were removed, replaced by eight 127mm AA ones, arranged in four twin mounts, the casemate mounts had their maximum elevation increased to 30°. The main guns maximum elevation was increased to 43°, sixteen 13.2mm machine gun mounts in four quadruple mounts were fitted. Armor belt was removed and replaced with a thicker 356mm (14-inch) one, tapering to 127mm fore and aft of the main gun barbettes. Because the increase of displacement would have increased draft by 0,5m to 9,6m (and as high as 10,18m at deep load), thus putting below the waterline a sizable portion of the main belt, the upper armor strakes were also increased in thickness to 203mm (8-inch). Deck armor was also increased to 140mm, with 55mm plates added over the quarterdeck to protect the steering gear. Another 88mm plate was added inside the bulges to augment the original 25mm ones in anti-torpedo protection. Extra bunkerage inside the bulges increased range to 9.000 nautical-miles (16.668km) at 16knots. Displacement increased to 34.435t standard and 39.586t at full load, but the engines were completely refurbished, with all the coal and mixed-firing boilers replaced by an all-oil-fired system (allowing for the removal of the fore funnel), powering the turbines to a maximum of 154.083shp, enough to propel the ship to 30knots. A catapult was fitted at the stern, and a collapsible crane added to operate two Nakajima E4N reconnaissance seaplanes, lattice platforms housing 110cm searchlights were erected around the funnel. Complement rose to 1.341 officers and men.
Subsequent sea trails revealed that, while the doubled engine power and increased speed made Inaba teorethically able to operate with the rest of Kokoan main battle fleet, her bow shape was not optimized for the new speed, making the foredeck unpleasantly wet, which, coupled with similar hydrodinamic issues around the bulge ends, made the ship quite the fuel hog on top speed, making any dash above 28-29knots undesirable unless strictly necessary. Despite the issues, once recommissioned, Inaba joined Kii and Owari to form Sentai 1, serving in that role until 1938, with the rebuilt Amagi replacing Kii in 1937.
[ img ]

In early 1936, under the second rearmement bill passed by Morimoto's government, a refit to bring Yagumo back to active service was approved. During works, at Hoshiguma Navy Yard, the main gun turrets and casemate mounts removed during the trining ship conversion -but kept in storage for this very same reason- were fitted back in place, with the exception of the two formemost casemate mounts, which were plated over. Overall, Yagumo underwent roughly the same modifications of her sister, athough with some differencies. Both fore and aft superstructures were of a different design, and most of the rangefinders and fire-control gadgets of a more advanced type. The searchlight platform around the funnel was also arranged differently in order to fit a machine gun director in a dedicated platform. Twenty 25mm machine guns in ten twin mounts were fitted as light AA guns instead of the quad 13.2mm ones of Inaba. Overall, the forward superstructure had larger greenhouses, enclosed spaces, and housed a more compact fire-control system for the secondary guns. More strikingly, the top of the pagoda tower was lower by two decks, with an open anti-aircraft command post fitted on top along a more advanced main gun director. Learning from Inaba's issues regarding seakeeping, speed and fuel consumption, Yagumo was fitted with larger and much more hydrodinamic bulges, and had her bow shape modified as well (also making the ship 209,3 m long overall, half a meter more than Inaba). This allowed the ship to hit the 30-knot top speed more smoothly and also increased the overall range to 10.000 nautical miles (18.520km) at 16knots. Displacement slighlty differed at 34.221t standard and 39.757t at full load. Aircraft complement was composed of two Nakajima E8N seaplanes. Lastly, the second starboard anchor, which had been left in place on Inaba, was removed.
[ img ]

Yagumo was recommissioned in early 1938 as the flagship of Sentai 2, joined by her sister Inaba for the first time in almost eight years. A refit to upgrade Inaba with the same fire-control equipment of Yagumo, solving the seakeeping, the fuel consumption issues and fitting of the anti-air command post was planned for 1941. Yet, by that year Koko shipyards all had their priorities focused on the Aricraft carriers, the Yashima class Battleship and the conversion of the Same-class submarine tenders into Light Carriers, other than the much needed Destroyer and Submarine construction. Thus, Inaba entered the pacific war still in her 1935 fit, effectively being the most oudated Battleship in Koko no Kaigun inventory.
In December 1941 Yagumo and Inaba were assigned to the Kokoan Aleutian invasion force, taking part in the Attu landings that happened on December 7th in an almost simultaneous fashion to the attack on Pearl Harbor and Midway Island. The two ships provided support by shelling American positions before troops were landed and remained in position until the 9th, when resistance was broken. The pattern repeated again two days later during the invasion of Kiska. On December 16, before the planned invasion of Adak they engaged an USN formation near Sequam island in the battle off Turf Point . With some luck from their side (Saratoga's task force was still too far to provide assistance) the Kokoan formation outnumbered and outgunned the enemy formation wich was made up by the light cruisers Richmond, Trenton and six destroyers. The American formation fought valiantly but was eventually overwhelmed by gunfire, with Trenton becoming a prime target for the entire Kokoan formation later in the battle. Eventually rolling over, exploding and sinking with all hands. The other US ships, each with their own share of damage, were forced to retreat while still being subjected to enemy fire.Yagumo spent the first part of the battle fruitlessly targeting Destroyers before switching fire to Trenton, although it is unclear, given the amount of shellfire the cruiser recieved, how much of the battleship fire had actually any other effect than accelerating its ultimate demise. Inaba initially fared better, shooting off one of USS Perkins funnels in the opening stages of the battle, but later suffered malfunctions of her fire control system and failed to land any more hits on target. She also suffered thirteen hits of various kind in return. Except for Inaba's few weeks needed to sail back home, get repaied and sail north again, the two ships kept being stationed in the Aleutians, in the event the Americans would have shown up in forces. During that time they supported the invasion of Atka and Amila islands in early May 1942. And they were also part of the fleet for the invasion of Umnak, Unalaska and Unimak that was cancleed after the disastrous defeat the IJN suffered off Midway in June.
After the months between July and october went by almost uneventfully, the two ships were deployed south to support the Kokoan and Japanese forces in the Solomon Islands. Yagumo stopped at Toumachi to repair a faulty boiler while Inaba proceded south, reaching the Solomons first on November 24th. While steaming south -with four destroyers escorthing- to join the screen of the Kokoan/Japanese carrrier force, Inaba became the unwanted target of an American attack. Two squadrons of dive bombers and one of torpedo bombers launched from the USS Saratoga stumbled upon the Battleship after they missed the carriers they were headed to attack during the aerial skirmishes of the day. The US airmen decided Inaba was a juicy enough consolation targed and attacked, hitting her with two torpedoes and five bombs. Despite listing and burning Inaba managed to evade further damage and, this time with much needed air cover, managed to reach Rabaul where she recieved some makeshift repairs to patch up underwater damage, then returned home for three months of repair at Toumachi. During the works Inaba had the two forward casemate guns removed, the second starboard anchor landed as well, the mainmast shortened and the floatplane complement upgraded to F1Ms. In addition, the pagoda tower was lowered by a level and fitted with an anti-air command platform, a new main gun director and a 10m rangefinder for fire-control. The woefully outdated anti-air armament of sixteen 13.2mm machine guns war removed and replaced by twenty 25mm machine guns in ten twin mounts, fitted in new platforms on the pagoda, around the funnel and near the aft superstructure. Two of the four searchlights were removed to make space for machine gun directors. Finally, the bow line was modified to address the speed and fuel consumption issues, slightly mitigating the problems.
[ img ]

In the meantime, Yagumo had reached Truk in December 1942, where she remained stationed until March 1943. The two ships were reunited again for the planned invasion of Espiritu Santo. They took part in the indecisive (tactical victory but strategic defeat) Battle off Torres Island. Here Inaba was damaged again by a bomb hit at midship, that damaged the n°3 gun turret, and two near misses, one of which temporarily jammed her rudder, necessitating another trip to the yards for repair. Yagumo in the meantime was redeployed at Midway Island, with Inaba joining her again in April after repairs were completed. On august 21st 1943 they sailed with the Kokoan carrier force that clashed with the US in the Battle of the Frigate Shoals (also known as Battle of Gardner). In the opening stages of the battle, planes from the USS Lexington and Cowpens, unable to break the protecting anti-air screen of the Kokoan carriers, choose to attack Inaba, hitting her with four torpedoes and four bombs. Counterflooding failed to correct the list and Inaba eventually capsized to starboard, taking 782 of her 1.387 crewmembers as she sank.
The surviving Yagumo remained stationed at Midway until December 1943, when US forces landed on Amila island. It was thus decided to redeploy the Battleship north to the Aleutians. Before that though, Yagumo reached Toumachi for a major wartime refit. All lower portholes on the hull were plated over, two F1M seaplanes replaced the earlier E8Ns, boat complement was reduced and the battle bridge recieved wind baffles. The anti-air suite was upgraded and increased to reach a total of 8 twin and 8 triple 25mm machine guns, 40 barrels overall. Radars were also embarked, two Type13 and one Type21 air-search sets, two Type22 surface sets and four TypeR4CA for anti-air guns. Crew complement had increased to 1.503 officers and men.
[ img ]

In this guise, Yagumo kept supporting operations in the Aleutians, shelling enemy positions and escorting convoys when they were nearing the islands. It was during this latter task that, on March 26th 1944, the Kokoan/Japanese formation was intercepted by an American squadron that had boldly circumnavigated the occupied islands to the north. What is known as the battle off the Komandorski islands began with US and Japanese cruisers exchanging fire until both Nachi and Salt Lake city were out of the engagement, by that point the Battleship Nevada had opened fire, causing the trasports to scatter and the Japanese Admiral in command of the fleet to order a retreat. Yagumo then positioned itself between Nevada and the convoy to screen its retreat. Both battleships opened fire, with Yagumo attempting to take advantage of its range and speed, but Nevada's fire appeared more accurate right from the start. Both ships hit each other multiple times, but ultimately Yagumo suffered the worst. Nevada landed more hits on target that, given Yagumo's lower armor belt (a flaw of the ship since the 1930's refit), ended up hitting and going through the 203mm upper belt. The kokoan battleship eventually turned into a mangled inferno as it stopped dead in the water. Nevada hit Yagumo another seven times before US radars picked up Kokoan land-based air squadron that had departed Attu looking for the American fleet. Neveda -which had in turn sustained substantial damage but was still mostly operational- and her escorts reversed course and sailed into safety. Eventually the convoy managed to regroup and still reach Attu later the same day.
Yagumo kept burning for another 20 minutes after the end of the engagement before going down. Only 142 survivors were picked up from the icy waters by the IJN Maya.

Ships in class: (laid down-launched-commissioned - fate)

Yagumo 1915-1917-1918 – Sunk 1944
Inaba 1917-1920-1921 – Sunk 1943

Shipbucket

Who is online