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My sincerest thanks to BB1987 for the redo of the B64-class battle cruisers for this AU.

By 1935, despite having been given extensive refits, it was obvious to all that the Amagi-class battle cruisers, let along the preceding Kongo-class, weren't going to be around forever. It was therefore decided to develop a new battle cruiser design. The hull selection was no problem, for the hull that had worked so well for the three classes of large cruiser was fairly easy to produce now that the shipyards that normally built major combatants had already built fourteen of them. The guns took some time to design, however, with the Naval General Staff wanting a ship that had bigger guns than the large cruisers, but not as large as the Amagis. Therefore, a new 12.2-inch gun was designed, and the ships were designed to mount three triple turrets.



The first ship, Tsushima, was laid down at the Yokosuka Navy Yard on 8 September 1940, with Hitachi and Chishima following in January 1941, and Hidaka that September. All were launched by mid-February 1943, and Tsushima was commissioned that September. She and sisters Hitachi and Chishima provided part of Ozawa's carrier screen at the Battle of the Philippine Sea in June 1944, and all four ships participated in the Battle of Leyte Gulf that October, with Hidaka barely three months in commission.

At the Battle of San Bernardino Strait, the class got its baptism of fire. The sisters also suffered their first loss between them, when Hitachi deliberately placed herself in the path of a twelve-torpedo spread originally intended for battleship Kitami. As sailors of both sides watched in horror, at least eight torpedoes slammed into the proud battle cruiser, ripping her apart and sinking her in seconds with only eight survivors. The other three ships were all damaged in various degrees, but managed to escape back to Brunei. Hidaka managed to add insult to injury when she scraped a reef while anchoring at Lingga, thereby necessitating her return to Japan for repairs.

In December 1944, Tsushima and Chishima were assigned to the San Jose Bombardment Force along with heavy cruiser Ashigara and light cruiser Oyodo. The force made it to the beachhead and commenced its bombardment mission, but PT-boats and air strikes soon forced the Japanese ships to concentrate on getting out alive rather than bombarding American ground forces. PT-boat attacks sank destroyer Kiyoshimo and hit Tsushima with two torpedoes, while air strikes put five torpedoes and seven bombs into Chishima, sinking her with heavy casualties. Tsushima lagged behind the rest of the Bombardment Force, but managed to escape towards Lingga. On 29 December 1944, she was only two hours from success when she was sighted by submarine U.S.S. Bergall. Three torpedoes ripped her apart, sinking her in minutes.

Hidaka spent the rest of the war running between Japanese naval bases, somehow managing to survive the war to enjoy a long and profitable career in the post-war IJN. She was decommissioned in April 1960 and has been part of the Hashirajima Fleet Museum since December 1966. She is currently Japan's only preserved battle cruiser.

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MS State Guard - 08 March 2014 - 28 January 2023

The Official IJN Ships & Planes List

#FJB

Again, my thanks to BB1987 for redoing these ships.

In early 1941, the Naval General Staff ordered two more Tsushima-class ships, but the Naval Construction Corps managed to get the additional vessels up-gunned to three triple 14-inch turrets, therefore making them an entirely new class: the Iwaki-class. Iwaki and sister ship Iwase were laid down in February and March 1942, respectively, with a further pair - Inaba and Iburi - ordered; these were laid down in February and March 1943, respectively.



The Iwaki-class ships did not start sliding down the building ways until late July 1943, and by the time Iwaki was commissioned on 20 January 1945, no large Japanese ships were venturing out of home waters. Iwase was caught off Kure in the massive air strikes on the Japanese homeland on 28 July 1945; hit by four 1,000-pound bombs and three torpedoes, she capsized and sank, joining Mutsu on the bottom of the Hashirajima fleet anchorage.

The last two ships of the class, Inaba and Iburi, didn't join the fleet until January and February 1946, respectively, by which time the war had reached the stage of ground combat on the Japanese home islands themselves. Upon commissioning, Inaba headed for Maizuru, where she was joined by Iburi in March. Iwaki was less fortunate; she was caught and sunk by the submarine U.S.S. Tirante off northern Japan on 14 June 1946 while attempting to reach Maizuru and her sisters. Inaba and Iburi, trapped in Maizuru, would be fortunate enough to join Hidaka as part of Japan's post-war fleet. They were decommissioned in December and October 1961, respectively; Iburi was scrapped in March 1977, and Inaba in May of the same year.

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MS State Guard - 08 March 2014 - 28 January 2023

The Official IJN Ships & Planes List

#FJB

Once more, thanks to BB1987 for the amazing work he did on these ships.

The next class of battle cruiser for the IJN warranted a redesign of the hull, but with pretty much the same superstructure. Aircraft handling facilities were moved aft, so as to enable the ships to eventually carry helicopters (as catapult aircraft were gradually being phased out). This enabled the superstructure to be brought closer together for much-cleaner lines, and when combined with the new hull style made for a very nice-looking vessel. The guns were further upgraded, this time to twelve 16-inch guns in four triple turrets.


The Suwa-class battle cruisers as planned, with seaplane facilities on the stern.

Four ships were ordered, and the first two, Suwa and Aki, laid down within four days of each other in late July 1943. The other two ships of the class, Suo and Omi, followed in late July and early August 1944, respectively. However, due to the extensive construction time for a capital ship, only Suwa and Aki were commissioned by the time the war ended in August 1946, with Suo and Omi still in the process of fitting-out.


The Suwa-class as completed in 1946, with the seaplane facilities removed and converted into landing space for auto-gyros.

All four ships would go on to serve for many years in the post-war IJN, but they were the last of their kind; no more battle cruisers would be built in Japan.


Suwa as she appeared in 1953, at the end of the 3rd Sino-Japanese War. All four vessels of this class proved themselves quite well in bombardment missions off the Chinese coast.


Suwa in 1968. She and the rest of the Japanese fleet alternated with U.S. Navy Task Groups in bombardment missions off Vietnam.

Post-1975, the four ships served as training vessels until finally being decommissioned between February 1994 and December 1995. Suo was stricken from the Navy List in January 1998, and was scrapped four years later in January 2002. Aki was stricken from the Navy List that same month, and was sent to the scrapyard in October 2003. Suwa was stricken from the Navy List in July 2009, followed by Omi in May 2010, and while Suwa was scrapped in April 2011, Omi is currently on donation hold. She is designated for the Tokyo Bay Fleet Museum and is currently scheduled to open in late June 2014.

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MS State Guard - 08 March 2014 - 28 January 2023

The Official IJN Ships & Planes List

#FJB

These are amazing!

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May you sail to glory forever. *salutes*

Very nice and very sleek looking. Interesting post-war perspectives too.

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I agree - nice work with drawings, and interesting ideas for post-war background.

Very nice and interesting designs. Only niggle I have is that it would be rather unlikely for all ships of that class at that size to be kept as museum ships after their service is done. Ships of this size and complexity are incredibly costly to maintain so unless your economy is very strong and there's persistent interest in them, you're better off only preserving one of the class and scrapping the rest. It's sad but that's the reality. You don't want to end up like the mess the USA is in with so many costly museum ships competing against each other that they're all in general money pits.

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"The first rule is not to lose; The second rule is not to forget the first rule"

The Oyodo-class light cruisers were designed as SubRon flagships, but didn't serve in this capacity until later. They were armed with the triple 6.1-inch turrets taken from the refitted Yamato-class battleships.


Oyodo as completed on 28 Febuary 1943. Note the different placements of searchlights and rangefinders from her later sister ships.


The second ship of the class, Niyodo, was completed on 27 August 1943 to a slightly different design, in that rangefinders and searchlights were situated differently. Oyodo was refitted similarly when she was converted to Combined Fleet flagship in early 1944.

The last two ships of the class were virtually identical, and Oyodo and Niyodo were refitted similarly, so eventually it was almost impossible to tell any of the quartet apart.


The third ship of the class, Tokoro, as commissioned on 26 February 1944.

All four ships were present at the Battle of Cape Engano, and helped rescue survivors of the sunken ships. In April 1945, Niyodo went with Yamato to Okinawa, and met her hand along with most of the other large ships in the task force. Oyodo was sunk in July 1945 in the massive air raids that month that targeted the remaining Japanese surface fleet. Tokoro and Omono remained in Tokyo Bay, acting as mother ships for Shinyo attack groups, midget submarines, and the Sen-Yu-Sho and Sen-Taka-Sho-class HA-type submarines, and were witnesses to the Tokyo Bay surrender ceremonies.


Omono in 1959. She and her sister served faithfully throughout the 3rd Sino-Japanese War. The former seaplane launching area was especially suited for helicopter operations.

In 1971, after 27 years of service, the two ships were decommissioned and laid up. Tokoro went to the scrapyard the following year, but Omono was transferred to the Maritime Safety Agency and became its flagship. To this day, she still holds the record of the largest ship ever having served with that agency.


Omono in 1972, with all armament removed and the forward superstructure lengthened and converted to accommodation and research space.

Omono's refit for service with the Maritime Safety Agency was not without its problems, however, as removal of all weapons drastically lightened the ship. Despite adding concrete ballast as a countermeasure, it was decided to find some smaller vessels to take her place, rather than put further funding towards correcting the problems. Omono went to the scrapyard in 1976.

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MS State Guard - 08 March 2014 - 28 January 2023

The Official IJN Ships & Planes List

#FJB

that last one is certainly going to get weight problems. you removed literally tons of her (in such an conversion like this it is also likely they lowered the fuel load or the engines or both, most likely both) so your ship is going to be higher in the water, with all the stability problems that poses. adding ballast to undo that change is gonna be a pain and a mess.

honestly, keeping the arnament but removing the guns itself only will be much cheaper. the sense of a ship like this in that service seems not very good either .

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Drawings are credited with J.Scholtens
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Shipbucket Wiki admin

Edited the class history to reflect ace's comments.

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MS State Guard - 08 March 2014 - 28 January 2023

The Official IJN Ships & Planes List

#FJB