WI: Shinano, Mutsu and an Unryu for Leyte Gulf

[Kantai Kessen]

As terribly as they did IRL. This provides zero help against Dart and Dace torpedoing Kurita's flagship, along with two other heavy cruisers, out from under him. Given the horrendous rout of Japanese air groups over Formosa, which included what few carrier air groups they had been able to scrounge together, I seriously doubt the Japanese would have been able to provide any aircraft at all for Kurama - not that 27 Zeroes would have done anything at all to slow down the American aerial strikes anyway. So she gets her teeth kicked in and probably at least a couple of other vessels.

All this means that Kurita's force arrives to Samar in much the same condition it did IOTL - battered, exhausted, and absolutely terrified of what the Americans might throw at them, all of which contributed to the "general attack" order that left his forces strung out in mutually unsupportable groups and then led to him losing his nerve. All he has are two or three more slow battleships, which really doesn't help him all that much. Maybe he sticks around long enough to destroy Taffy 3, in which case Taffy 2 and Task Group 38.1 rip him a new asshole.

Though that runs on the assumption that Kurita still turns around, inadvertently fooling Halsey into thinking he was retreating for good. American aerial attacks will be concentrated on Kurama - it's entirely possible that after Sibuyan Sea Kurita isn't shaken enough to turn around and keeps pressing for San Bernardino Strait. At which point Halsey pretty much has to form Task Force 34 - probably with all six of his battleships this time - to block the strait while he goes after what he thinks is the more dangerous force: Ozawa's carriers. Hell, the presence of Kurama is going to reinforce his thinking, because the Americans suspected Unryu and Amagi were part of Ozawa's force and six carriers unchecked are a dangerous force.

In which case... well, I can't exactly call "sinking some cruisers and destroyers and mauling a couple of battleships in exchange for near-total annihilation" to be an improvement over Samar.

I was thinking that the Kates aboard Kurama could provide ASW patrol. Surely they have at least a chutai available for such an important operation. It's also worth noting that when Darter and Dace were moving to attack Centre Force, they did so on the surface and transmitted radio signals that were picked up by Yamato.

Thus easier detection of the subs? Would a non-torpedoed Kurita make better decisions - such as actually forming a line of battle at Samar?

Kurama, being an Unryu, probably won't take much to sink, so a battleship may go to the bottom with her. If it is Shinano, though, the IJN will have a better chance compared to losing the vastly more experienced Musashi.

 

[NOMISYRRUC]

Let us also assume that, due to the resources freed up from Shinano's conversion (which took up the materials for two Unryu-class ships), the IJN gets an extra Unryu-class carrier assigned to Centre Force to provide some CAP and ASW cover. Say that this ship is called Kurama. She carries 27 Zeroes and 9 Kates (or some other air group - please describe what the IJN would have available for her), also has enough fuel to get to Leyte and back, and has had three months of training.

The Battle of Leyte Gulf began on 23rd October 1944 and ended on 26th October 1944.

The IJN had three Unryu class aircraft carriers at that time.

Unryu completed 6th August 1944​

Amagi completed 10th August 1944​

Katsuragi completed 15th October 1944​

These ships were laid down between August and December 1942.

Three more Unryu class ships (named Kasagi, Aso and Ikoma) were under construction. They had been laid down between April and July 1943 were launched in October and November 1944.

Any resources "freed up" by completing Shinano as a battleship instead of an aircraft carrier would have been used to accelerate the completion of these ships. It's unlikely that the ships laid down in 1943 could be made ready to take part in the battle. However, it might be possible to have the first three completed early enough to have had at least three months of training before the battle started.

However, as others have noted the denominator was a shortage of "trained" aircrew rather than a shortage of flight decks. I wrote trained in inverted commas because there was no comparison between the standard of training of USN and IJN carrier aviators at this time.

Unryu and Amagi had been in commission for two months at the time of the battle and I suspect that a shortage of aircrew was what prevented them from taking part.

Only four of the six aircraft carriers survived the Battle of the Philippine Sea took part in the Battle of Leyte Gulf. They were Chitose, Chiyoda, Zuiho and Zuikaku with 116 aircraft embarked (according to the Wikipaedia) but their theoretical capacity was 153 aircraft (27 each for the 3 light carriers and 72 for Zuikaku). One of the two absentees was Junyo which had been badly damaged at the Philippine Sea. The other was Ruyho which (according to Wikipaedia) was ferrying aircraft to Taiwan when Leyte Gulf started and I suspect that she would have been used as an operational aircraft carrier in the battle had enough aircraft and aircrew been available.

Therefore, the Japanese had seven aircraft carriers with a combined capacity of 306 aircraft available at the start of the battle, but were only able to deploy four ships with 116 aircraft. (The three ships that didn't take part were Amagi, Ruyho and Unryu.) However, ITTL it might be possible complete Katsuragi two or three months earlier which would increase the force to 8 ships with a combined capacity of 369 aircraft.

Another problem was that at the start of the battle the aircraft carriers were in Japan so they could be close to the flying training schools and the battleships were in the East Indies to be closer to the oil supply. That the main reason why the Japanese forces were deployed the way they were.

If they did have enough aircrew to form eight full strength air groups they could have rotated them between Japan and the East Indies. In that situation Kurita's force might have been defended by two Unryu class aircraft carriers with a combined air group of 108 Zero fighters and 18 Kates for ASW.

However, that's a lot of "ifs" which would require a lot of PODs, which would include introducing a convoy system sooner (which would pay particular attention to the protection of the tanker traffic to Japan) and a training organisation that was producing more and better aircrew.

 

[Kantai Kessen]

Chances are better than average that rather than losing just one of the Yamatos, they lose all of them. With the addition of two battleships Kurita is much less likely to turn away and trust to his substantially more powerful force to carry the day. There is also a not insignificant chance that with two additional BB in the TF that Darter selects one of them as here target rather than the Atago. If Kurita doesn't have his ship shot out from under him there is a substantially greater chance that his later decision making is altered.

Even if he doesn't turn away either during the Sibuyan Sea engagement or off Samar and Halsey still gets buck fever (which is still very likely since "he was not going to make the same mistake" the Spruance made in Philippine Sea) and pushes on, what does he actually accomplish? His cruiser force was effectively destroyed, his destroyers are miles behind his main body and he still has 300+ aircraft from the other two Taffy groups to deal with, along with their escorting destroyers and destroyer escorts (which have already demonstrated their lethality with Taffy Three) in what would be hour, maybe two hour, running gunfight while under heavy air attack. He then has to pass through a very narrow strait (about 8 miles of navigable water for his heavies) before entering the Gulf proper. Once in the Gulf the force faces a minimum two hour sail to reach the transports remaining in the Gulf (most of the transports had departed from the initial landing force and the reinforcement groups *i.e. the second wave of supplies* were still a day away, having left Hollandica only on the 23rd. There is a common misconception that there were several hundred transports/LST/LSD bobbing at anchor in the Gulf, in reality the landing fleets ITF 78 & 79) were sending out ships as early as mid day on the 20th as soon as they had off loaded and could be reassembled with a ASW escort they were sent back to be reloaded (and to get them away from possible enemy air or submarine attack).

By the time Kurita has fought his way through the Taffys and around 25 destroyers remaining in the Gulf (worth keeping in mind what Taffy three three DD and five DDE managed, while Kuritia force was relatively fresh and organized) TF 38.1's second airstrike of the morning against Kurita will be overhead, with the rest of TF 38 a few hours hours behind? Sure there may be some transports sunk, most of them empty, along with a few more U.S. escorts, but that would be the only real change on the American side. Japanese probably lose the entire force, down to the last destroyer.

As far as an additional carrier with the Northern Force with a few attack aircraft and a Chutai or two of fighters it help the Japanese not at all. Might get a couple USN pilots a Navy Cross.

`What I meant to say was that Kurama would accompany Centre Force, NOT Northern Force. Kurita needs some air cover and it's not going to be coming from the land after what happened at Formosa.

 

[Resurgam]

Wait - what was the semi-option for Kamikaze pilots?

I've read accounts of not-so-willing pilots saying "Oh, sorry, never saw a target of opportunity" and surviving the war that way.

 

[Kantai Kessen]

The Battle of Leyte Gulf began on 23rd October 1944 and ended on 26th October 1944.

The IJN had three Unryu class aircraft carriers at that time.

Unryu completed 6th August 1944​

Amagi completed 10th August 1944​

Katsuragi completed 15th October 1944​

These ships had been laid down between August and December 1942. Three more, named Kasagi, Aso and Ikoma were laid down between April and July 1943 that were launched in October and November 1944.

Any resources "freed up" by completing Shinano as a battleship instead of an aircraft carrier would have been used to accelerate the completion of these ships.

However, as others have noted the denominator was a shortage of "trained" aircrew rather than a shortage of flight decks. I wrote trained in inverted commas because there was no comparison between the standard of training of USN and IJN carrier aviators at this time.

Unryu and Amagi had been in commission for two months at the time of the battle and I suspect that a shortage of aircrew was what prevented them from taking part.

Only four of the six aircraft carriers survived the Battle of the Philippine Sea took part in the Battle of Leyte Gulf. They were Chitose, Chiyoda, Zuiho and Zuikaku with 116 aircraft embarked (according to the Wikipaedia) but their theoretical capacity was 153 aircraft (27 each for the 3 light carriers and 72 for Zuikaku). One of the two absentees was Junyo which had been badly damaged at the Philippine Sea. The other was Ruyho which (according to Wikipaedia) was ferrying aircraft to Taiwan when Leyte Gulf started and I suspect that she would have been used as an operational aircraft carrier in the battle had enough aircraft and aircrew been available.

Therefore, the Japanese had seven aircraft carriers with a combined capacity of 306 aircraft available at the start of the battle, but were only able to deploy four ships with 116 aircraft. (The three ships that didn't take part were Amagi, Ruyho and Unryu.) However, ITTL it might be possible complete Katsuragi two or three months earlier which would increase the force to 8 ships with a combined capacity of 369 aircraft.

Another problem was that at the start of the battle the aircraft carriers were in Japan so they could be close to the flying training schools and the battleships were in the East Indies to be closer to the oil supply. That the main reason why the Japanese forces were deployed the way they were.

If they did have enough aircrew to form eight full strength air groups they could have rotated them between Japan and the East Indies. In that situation Kurita's force might have been defended by two Unryu class aircraft carriers with a combined air group of 108 Zero fighters and 18 Kates for ASW.

However, that's a lot of "ifs" which would require a lot of PODs, which would include introducing a convoy system sooner (which would pay particular attention to the protection of the tanker traffic to Japan) and a training organisation that was producing more and better aircrew.

If the Unryus are completed earlier thanks to Shinano, could we assign them to Northern Force and the light carriers to Centre Force instead? Better suited in terms of seed and more decks, so more insurance.

This means Zuiho, Chitose and Chiyoda, with 90 planes (30 each), probably 72 Zeroes and 18 ASW Kates. Unlikely, but possible. Perhaps Ryuho as well if there is fuel, but I wouldn't recommend it; she is far too vulnerable.

Of course the bane of the IJNAS will rear its head in the shape of insufficiently trained pilots - which is something that needs to be fixed pre-war.

 

[Kantai Kessen]

I've read accounts of not-so-willing pilots saying "Oh, sorry, never saw a target of opportunity" and surviving the war that way.

Ah; never heard that one.

 

[Resurgam]

Ah; never heard that one.

It's been a while since my Intrepid days - I read those accounts then for WWII tours, but there were definitely pilots who were not told what this was going to entail and went "...wait, what?!" and survived the war by always saying they couldn't target an American ship, so they didn't try.

A bit like those in police battalions in Poland who refused to engage in any "actions" and were told to guard a bus (see No Ordinary Men).

 

[NOMISYRRUC]

Of course the bane of the IJNAS will rear its head in the shape of insufficiently trained pilots - which is something that needs to be fixed pre-war.

However, that's a lot of "ifs" which would require a lot of PODs, which would include ... a training organisation that was producing more and better aircrew.

 

[NOMISYRRUC]

If the Unryus are completed earlier thanks to Shinano, could we assign them to Northern Force and the light carriers to Centre Force instead? Better suited in terms of seed and more decks, so more insurance.

This means Zuiho, Chitose and Chiyoda, with 90 planes (30 each), probably 72 Zeroes and 18 ASW Kates. Unlikely, but possible. Perhaps Ryuho as well if there is fuel, but I wouldn't recommend it; she is far too vulnerable.

Of course the bane of the IJNAS will rear its head in the shape of insufficiently trained pilots - which is something that needs to be fixed pre-war.

As I wrote, IOTL the aircraft carriers were in Japan to be close to the training schools and the battleships were in the East Indies to be close to the oil. Therefore, the extra ships would be assigned to the Northern Force by default.

However, I was suggesting that ITTL the Japanese were (due to several PODs) able to train three times as many aircrew and had eight aircraft carriers available (instead of seven) so they might rotate them between Japan and the East Indies. I didn't put it in my previous post, but what I was thinking of was organising the eight ships into four divisions of two ships - two divisions of two large aircraft carriers and two divisions of two ships of the Zuiho type. Therefore, one of the four divisions would be with the battleships in the East Indies by rotation and it would happen to be that the division with two of the Unryus would be in the East Indies when the Americans attacked. I deliberately did that so that Kurita's force would have been defended by 126 aircraft instead of 54-60 including 108 fighters instead of 36.

Ryuho took part in the Philippine Sea - therefore she would have been at Leyte Gulf had the fuel and aircraft been available - The Japanese were that desperate.

 

[NOMISYRRUC]

Imagine that, in addition to the ships that VAdm Takeo Kurita possesses in the IJN's Centre Force at Leyte Gulf, he also has the Shinano, completed as a proper battleship instead of a crappy carrier, and the Mutsu, which doesn't blow up in 1943. This gives Centre Force the following capital ships: Yamato, Musashi, Shinano, Nagato, Mutsu, Kongo, Haruna. Assume that there is enough fuel for them to take part in the operation, and that both ships were also able to participate in the Battle of the Phillippine Sea, so the Shinano in particular has some combat experience.

I think that converting Ise and Hyuga to hybrid battleship-carriers was a waste of resources even if the aircraft and aircrew had been available. The materials used for their OTL conversions might be used to accelerate the completion of the six Unryu class built ITTL.

They would have been in the East Indies with the rest of the battleships if they hadn't been completed, which gives the Japanese the opportunity to have Yamato, Musashi, Shinano, Nagato, Mutsu, Fuso, Yamashiro, Ise and Hyuga assigned to the Centre Force with Kongo and Haruna in the Southern Force. However, I admit that it is more likely that Ise and Hyuga would have reinforced the Southern Force and been sunk without inflicting any damage upon the enemy.

It would also help if you avoided the Hyuga's turret explosion of May 1942, which I think is allowable as you have avoided Mutsu's magazine explosion.

 

[NOMISYRRUC]

Imagine that, in addition to the ships that VAdm Takeo Kurita possesses in the IJN's Centre Force at Leyte Gulf, he also has the Shinano, completed as a proper battleship instead of a crappy carrier, and the Mutsu, which doesn't blow up in 1943. This gives Centre Force the following capital ships: Yamato, Musashi, Shinano, Nagato, Mutsu, Kongo, Haruna. Assume that there is enough fuel for them to take part in the operation, and that both ships were also able to participate in the Battle of the Phillippine Sea, so the Shinano in particular has some combat experience.

Why not do it properly and complete No. 111 too? Then the Centre Force would have Yamato, Musashi, Shinano, No. 111, Nagato, Mutsu, Kongo, Haruna.

And while you're at it have No. 111 completed as a battleship instead of scrapping her on the slips. According to Conway's 1922-46 both ships were suspended in December 1941 when No. 110 was 50% complete and No. 111 was 30% complete. It doesn't give the exact date when the decision to complete No. 110 as an aircraft carrier (Shinano) and scrap No. 111 was taken. It only says that the decision was made in 1942 and doesn't say when work on No. 110 resumed.

However, I have another source that says this.

Source: Page 21 of Japanese Monograph-149 - Outline of Naval Armament and Preparations for War - Part 2

IOTL No. 110 was completed as an aircraft carrier was because it was easier to launch her than dismantle her. Had she not been suspended in December 1940 or December 1941 and June 1942 (depending upon which source is correct) it might have been easier to complete her as a battleship instead of as an aircraft carrier. Similarly had No. 111 not been suspended for 6 or 18 months to June 1942 (depending upon which source is correct) it might have been easier to complete her than dismantle her.

However, the most likely result is that the American aviators would sink an extra target.

 

[Virginia Liberal]

Wait - what was the semi-option for Kamikaze pilots?

It was a " voluntary" act of self sacrifice at least at first

 

[Kantai Kessen]

Why not do it properly and complete No. 111 too? Then the Centre Force would have Yamato, Musashi, Shinano, No. 111, Nagato, Mutsu, Kongo, Haruna.

And while you're at it have No. 111 completed as a battleship instead of scrapping her on the slips. According to Conway's 1922-46 both ships were suspended in December 1941 when No. 110 was 50% complete and No. 111 was 30% complete. It doesn't give the exact date when the decision to complete No. 110 as an aircraft carrier (Shinano) and scrap No. 111 was taken. It only says that the decision was made in 1942 and doesn't say when work on No. 110 resumed.

However, I have another source that says this.

View attachment 621971
Source: Page 21 of Japanese Monograph-149 - Outline of Naval Armament and Preparations for War - Part 2

IOTL No. 110 was completed as an aircraft carrier was because it was easier to launch her than dismantle her. Had she not been suspended in December 1940 or December 1941 and June 1942 (depending upon which source is correct) it might have been easier to complete her as a battleship instead of as an aircraft carrier. Similarly had No. 111 not been suspended for 6 or 18 months to June 1942 (depending upon which source is correct) it might have been easier to complete her than dismantle her.

However, the most likely result is that the American aviators would sink an extra target.

If No. 111 is completed (let us call her Izumi) then we have a division of speed in the IJN's battleline:

• 31 knots: Kongo, Haruna
• 28 knots: Yamato, Musashi, Shinano, Izumi
• 25 knots: Nagato, Mutsu, Ise, Hyuga, Fuso, Yamashiro

We can perhaps attach all the 25-knotters to the Southern Force, which will give Oldendorff a much harder time. The six ships left over for the Centre Force are only one more than actually assigned, so there will be a better (that is, more manageable) ratio of escorted ships to escorts.

Can we build more DDs at the same time?

 

[Kantai Kessen]

As I wrote, IOTL the aircraft carriers were in Japan to be close to the training schools and the battleships were in the East Indies to be close to the oil. Therefore, the extra ships would be assigned to the Northern Force by default.

However, I was suggesting that ITTL the Japanese were (due to several PODs) able to train three times as many aircrew and had eight aircraft carriers available (instead of seven) so they might rotate them between Japan and the East Indies. I didn't put it in my previous post, but what I was thinking of was organising the eight ships into four divisions of two ships - two divisions of two large aircraft carriers and two divisions of two ships of the Zuiho type. Therefore, one of the four divisions would be with the battleships in the East Indies by rotation and it would happen to be that the division with two of the Unryus would be in the East Indies when the Americans attacked. I deliberately did that so that Kurita's force would have been defended by 126 aircraft instead of 54-60 including 108 fighters instead of 36.

Ryuho took part in the Philippine Sea - therefore she would have been at Leyte Gulf had the fuel and aircraft been available - The Japanese were that desperate.

Ah, now I understand. Interesting POD - I shall think on it.

 

[ShySusan]

Why not do it properly and complete No. 111 too? Then the Centre Force would have Yamato, Musashi, Shinano, No. 111, Nagato, Mutsu, Kongo, Haruna.

And while you're at it have No. 111 completed as a battleship instead of scrapping her on the slips. According to Conway's 1922-46 both ships were suspended in December 1941 when No. 110 was 50% complete and No. 111 was 30% complete. It doesn't give the exact date when the decision to complete No. 110 as an aircraft carrier (Shinano) and scrap No. 111 was taken. It only says that the decision was made in 1942 and doesn't say when work on No. 110 resumed.

However, I have another source that says this.

View attachment 621971
Source: Page 21 of Japanese Monograph-149 - Outline of Naval Armament and Preparations for War - Part 2

IOTL No. 110 was completed as an aircraft carrier was because it was easier to launch her than dismantle her. Had she not been suspended in December 1940 or December 1941 and June 1942 (depending upon which source is correct) it might have been easier to complete her as a battleship instead of as an aircraft carrier. Similarly had No. 111 not been suspended for 6 or 18 months to June 1942 (depending upon which source is correct) it might have been easier to complete her than dismantle her.

However, the most likely result is that the American aviators would sink an extra target.

My question is, if they keep building 110 and 111, what aren't they building instead? Were the Japanese able to use the resources freed up by suspending the two ships to build other, more vital ships like carriers, destroyers or tankers?

 

[steamboy]

My question is, if they keep building 110 and 111, what aren't they building instead? Were the Japanese able to use the resources freed up by suspending the two ships to build other, more vital ships like carriers, destroyers or tankers?

Yeah that's the big issue with the Yammy's, they consumed huge amounts of limited resources. Build them and other things will simply not be built.

 

[NOMISYRRUC]

My question is, if they keep building 110 and 111, what aren't they building instead? Were the Japanese able to use the resources freed up by suspending the two ships to build other, more vital ships like carriers, destroyers or tankers?

Indeed. That's one of the reasons why they were suspended in the first place.

 

[ShySusan]

Yeah that's the big issue with the Yammy's, they consumed huge amounts of limited resources. Build them and other things will simply not be built.

Indeed. That's one of the reasons why they were suspended in the first place.

That's what I thought, but I wasn't sure. I knew even the US had to suspend construction of some ships to free up resources to build more needed ships like destroyers and LSTs so it stood up reason that Japan would have to as well.

 

[Kantai Kessen]

That's what I thought, but I wasn't sure. I knew even the US had to suspend construction of some ships to free up resources to build more needed ships like destroyers and LSTs so it stood up reason that Japan would have to as well.

Perhaps not trying to build sixteen Unryus would help.

 

[Kantai Kessen]

Indeed. That's one of the reasons why they were suspended in the first place.

Ironically, they are very important in the scenario we're considering if we want to give the IJN even a hope of victory. They're the only BBs they have that can stand up to the modern USN battleline.