completing another destroyer class
Shizuha Class Destroyer:
As the London Naval Treaty entered into effect the only possible way for Koko no Kaigun to keep building destroyers was to retire older units. The Kuchikukan-15 and -27 Classes and the lone Sato were those upon which the choiche befell, converted into patrol boats or relegated to training duties. Given the number of Yuuka and Reisen class ships that were still to enter service, only four extra units could have been built. More so, they must have displaced no more than 1.500T because the Reisens ate all the extra tonnage allowances permitted by the treaty.
In november 1930 the Naval Staff issued the requirement for a new class of destroyers to be built. With said requirement of a maximum 1.500T displacement at standard load KnK designers ended up joining the IJN ones to develop a design. The resulting ship would have been 109,5m long, 10 abeam and drafting 3,3 for a planned displacement of 1.400T, the armament called for five 5-inch guns (127mm) and nine 610mm torpedo tubes in triple launchers to be installed, top speed was planned at 36knots for a range of 4.000nm at 14knots. The ships were ordered in Japan as the Hatsuharu Class and as the Shizuha Class in Koko.
The lead ship, Shizuha, was laid down at Kumoi Arsenal on December 18th 1931 and launched on December 17th 1932. While she was still fitting out, IJN Hatsuharu trials revealed the ship to be prone to roll heavily, demonstrating that her metacentric height was too low. As a contermeasure the upper levels of Shizuha's bridge were reduced in size and bulges were added, bringing the overall beam to 10,6m. The rudder was modified to improve handling during turns. As completed Shizuha turned out to be some 40 tons lighter than an Hatsuharu, displacing 1.490T instead of 1.530. Still both ships were overweight compared to their planned design.
The second ship of the class, Minoriko, was laid down December 31st 1932 at Kumoi arsenal shortly after the launch of Shizuha. The last two units, Hina and Nitori, started construction at Kousaten Navy Yard in late 1933. In March 1934 Minoriko was roughly two months away from launch when the IJN torpedo boat Tomozoru disastrosly capsized during night torpedo trials off Sasebo. The incident prompted an immediate revision of all ships currently under construction or recently completed for both the IJN and KnK, with the Hatsuharu/Shizuha beign among the most deficent ones when it came to stability and topweight issues. Construction on the three ships was halted and Shizuha was taken out of service while designers returned to the drawing board to find a solution for the problems. Japanese Hatusharus had their bridgework and armament reduced to counter topweight, and ballast led to a lowered top speed from 36 to 33 knots, Kokoan Shizuhas went through a much more extensive and complex rebuilds.
In the time that elaped between their construction approval and the Tomozoru incident, Koko had experienced a government change and a coup d'etat that ultimately strenghtened Kusako Morimoto's leadership. As soon as his new cabinet took office a naval rearmament plan was immediately approved, progressively disregarding treaties as it would later proved by the joint Kokoan/Japanese denunciation of the Washinton Naval treaty in december 1934.
Under the new provisions designers scrapped the 1.500T weight limitations and drafted a new ship from the old plans with no restrictions in mind. By fall 1934 works restarted on Minoriko, Hina and Nitori. In an overly complex fashion the hull was cut apart at midship and a newly built 2,3m section was added bringing the total length of the ships to 111,8m and the beam to 10,1. The engines were replaced with new boilers generating 56.000shp installed in place of the planned 40.000shp ones. Supestructure volume was vastly reduced, the funnels cut down and the entire aft deckhouse replaced by a much smaller structure. The forward, superfiring, single 127mm gun was moved to the quarterdeck and all three triplee torpedo launchers were landed, replaced by two quadruple sets. A new, larger, rudder was also installed and the hull strengthened. The large-scale rebuild strained to the brim the capabilities of the shipyards involved, but in effectively turned the three destroyers into new ships. Their displacement had risen from 1.490 to 1.796T, also increasing draft to 3,5m, but thanks to the increased engine power the top speed fell by just 0,3knots from 36 to 35,7. Minoriko, Hina and Nitori were eventually commissioned between August and November 1935. Shizuha was docked at Toumachi Naval arsenal to underwent a similar, massive reconstruction, eventually rejoining the fleet modified like her sisters by early March 1936.
The first rearmament bill not only disregarded treaty limitation concerning weigth, but also called for a restart in Destroyer production. On October 24th 1934 five more ships of the Shizuha class were ordered, this time to be built from the start to the modified design. The first ship, Momiji, was laid down at Kousaten Navy Yard by the end of the year, two more, Mion and Kanako, followed in 1935 and another two, Suwako and Iku, in 1936. Their orders split between Toumachi and Hoshiguma Naval Yards. When in September 1935 many IJN vessels were damaged in what will be later known as the Fourth Fleet Incident the design of the five newer ship was revised once again, relocating armament and deckhouses placement and reducing the bridge for more topweigh-saving measures, although lenghtening building time. The so-called second batch of the Shizuha class, also known as Type II or Momiji subclass had its ships entering service between 1937 and 1939. The ships displaced 1.788T, slightly less than the four earlier sisters. They sported newer gun turrets and more advanced fire-control equipment, other than an increased depth charge complement, dedicated RDF room and twin 13mm machine gun as light anti-air guns in place of the 40mm ones fitted on the other ships of the class.
Overall, while the massive rebuild the ships solved the topweight and stability issues allowing to retain almost of the armament and speed of the original design the works were so extrensive that they stretched the shipyards capabilities to the point that just nine ships were built over the course of eight years despite beign ordered on four different shipyards. This, coupled with other slipways beign committed to the building of other ships under the rearmament plans, prevented the restart of full-sized destroyer production until 1937 despite it was intended to ignore treaty limitations since December 1934.
In late 1940 all ships recieved a degaussing cable, and hydrophone and had their anti-air armament upgraded to either two twin 25mm machine guns (Shizuha through Nitori) or two triples (Momiji trough Iku).
At the start of the Pacific War all sisters were involved in the invasion of Midway. After that they were deployed to Indonesian waters to support Japanese operations in the Dutch East Indies and took part in the naval battle of Balikpapan. Based at Singapore from late february to mid May 1942 they kept supporting Japanese and Kokoan operations before returning home to join the main force of operation AL-MI. Like all other surface ships involved, they played no part in the subsequent battle.
All fitted with an extra twin 25mm piece on a platform forward of the bridge, the nine sisters then took part in most operations around the Solomon islands from late 1942 to June 1943. Here Shizuha would be lost to an enemy submarine in April and Kanako to aircrafts two months later.
As Koko no Kaigun attentions shifted north, the destroyers returned home. All recieved a Type22 surface search radar and were painted in black and white arctic camouflage. Redeployed to the Aleutians, Hina and Momiji would be lost as well by the end of the year.
The battered five survivors were then recalled in stints for a major wartime refit. The two remaining ships of the original batch, Minoriko and Nitori, were considered less structurally sound and capable of handling extra weight, so they had thier single 127mm turred removed to relieve topweight issues. A deckhouse with a triple 25mm machine gun platform was added aft, together with twelve single 25mm pieces. A TypeR2FA air-search radar was installed on the aft mast and lower deck portholes sealed.
The three Type II ships, Mion, Suwako and Iku, were in better material condition and were given a more extensive overhaul. The single 127mm gun was retained, and two 25mm triple machine gun mounts were added on new platforms abaft the fore funnel, augmented by another nine single mounts. The TypeR2FA air-search radar was added, but fitted on the foremast as well, deleting the crow's nest entirely, and a Type R4Ca fire-control radar added on the integrated director-rangefinder set on top of the bridge, which was expaned with the addition of a dedicated radar room. Many portholes were sealed as well.
Eventually two more ships would be lost during 1944. As 1945 dawned, Minoriko was the sole survivor of the original batch of four and badly needed another refit. During works the anti air-armament was further increased to thirty-one barrels (three triple, one twin and twenty singles). The Type 22 air-search set was replaced by a more advance Type33-kai and the split director-rangefinder set was replaced by an integrated one fitted with a TypeR12CAD fire-control radar. An IFF set was fitted, more portholes were sealed and, by the second half of the year, a late war blue-black camouflage painted.
The surviving Type II ships (Mion and Iku) followed similar lines but recieved more upgrades. They recieved a sonar set, a Type64 High-Frequency RDF and two twin mounts of the new 40mm Type5 machine guns in place of their midship torpedo reload set (for a total of two twin 40mm, four triple, one twin and thirteen single 25mm pieces).
Mion was sunk in late 1945 during the massive US offensive against the Aleutians that took place during Koko uprisings. During the subsequent co-belligerant timeframe that Koko went through sfter its surrender Minoriko was interned to Midway. Iku was instead brought into service under Amagi squadron and repainted in USN Measure22 scheme, taking part in naval operations around Okinawa.
The two surviving ships were both decommissioned shortly after the end of the war and scrapped in 1947/48.
Ships in class: (laid down-launched-commissioned - fate)
Shizuha 1931-1932-1933 - Sunk 1943
Minoriko 1932-1934-1935 - Decommissioned 1946
Hina 1933-1934-1935 - Sunk 1943
Nitori 1933-1934-1935 - Sunk 1944
Momiji 1934-1936-1937 - Sunk 1943
Mion 1935-1936-1937 - Sunk 1945
Kanako 1935-1936-1937 - Sunk 1943
Suwako 1936-1937-1938 - Sunk 1944
Iku 1936-1938-1939 - Decommissioned 1946