The IJN's July 1942 Reorganization: What if they had doubled down on the Kido-Butai strategy instead?

[Glenn239]

We know what happened. In April 1942 Yamamoto conceived of a plan to crush the US carrier fleet, allowing the IJN total aerial domination in most places of the Pacific at least to the end of 1943. Nagumo's Kido Butai, four carriers strong, then went to Midway in June and all four of these carriers were destroyed. At a stroke, the IJN's carrier aircraft capacity had been reduced from about 580 to about 310. After the battle, the Japanese navy re-organized its naval and air forces in July 1942. This can be found here,

Imperial Japanese Navy, 14.07.42

At the time of the reorganization not all units listed were at their authorized strengths of a total of 1375 aircraft. In particular, the carrier forces required some number of months to work up to full strength, approximately as follows:

Zuikaku, Shokaku, Ryujo: August 15th
Zuiho: August 28th
Junyo, Hiyo: October 4th
Ryuho: Re-commissioned as a carrier on November 30th, (no air group)

The July 1942 reorganization of naval air forces, not including bi-planes or A5M4 Claudes, was as follows

Having lost four fleet carriers at Midway, only 25% of the IJN’s available aircraft were assigned to the carrier fleet, (a total of 324 aircraft and seaplanes aboard 3rd Fleet carriers and cruisers). Given that at this time the US fleet carriers would never challenge anywhere close to major Japanese air bases, this arrangement was an insufficient advantage against the USN’s fleet carriers, (Saratoga, Enterprise, Hornet, Wasp) in any realistic sea battle scenario. These US carriers had a combined combat capacity of about 314 aircraft:

USN Fleet Carriers:

122 x F4F fighters
134 x SBD dive bombers
58 x TBF torpedo bombers
Total: 314 aircraft

What if the July 1942 Reorganization was more Carrier-centric?

Objective

The purpose of the proposed reorganization is to go 'all in' on the original 1st Air Fleet concept of maximum aerial force concentrated to deliver one decisive blow to cripple the US carriers. Then, for the superior IJN surface forces to advance and sink them with gunfire, giving the IJN absolute carrier supremacy in the Pacific and Indian Oceans into 1943. All six remaining IJN carriers, (excluding Hosho) would therefore need to operate in one group to deliver the heaviest blow possible, like what was intended at Midway. Immediately after the carrier action was completed, Nagumo's carriers would draw near to Rabaul and the depleted torpedo and fighter groups would rotate ashore to reconstitute, while the shore-based carrier group reserves would rotate aboard to allow Nagumo’s fleet to quickly resume the offensive with fresh forces.

Zuikaku and Shokaku

The killing force of IJN aviation in 1942 was in its carrier based torpedo bombers. These required large well trained formations in order to deliver the multiple hits necessary to slow a US carrier enough that IJN surface forces could catch and destroy them. Only the ‘kakus were able to carry this size of Kate establishment. Shokaku and Zuikaku therefore discard with Val dive bombers altogether, instead equipped with oversized torpedo air wings of 54 bombers each. This allows for six torpedo attack units of 18 Kates per US carrier, each attack unit enough on its own to cripple one carrier. Once crippled, the IJN surface forces then advance under the cover of Zeroes to destroy the US carriers, which are unable to flee at top speed due to torpedo damage.

The first wave of 54 torpedo bombers would be 18 each of the B5N2’s. But, because of the shortage of B5N2’s in the second half of 1942, the 2nd Wave groups would comprise one wave of eighteen B5N2’s, one wave of eighteen B5N1’s, and one wave of mixed B5N2’s and N1’s. The B5N1’s cruised at a slower speed, meaning that the second wave may be more strung out than the first.

Deck Park: These carriers will each have a deck park of nine A6M2 Zeroes each.

Hiyo and Junyo.

These carriers were slower and shorter in deck length than the Kaku’s, making them less suitable for torpedo bombers. The 36 dive bombers assigned to these carriers are intended to accompany the first wave to deliver combined arms assault tactics. The carriers themselves can act as munitions reserve for the big fleet flattops, if this proved necessary. The oversized fighter establishment is for defensive CAP operations as well as to establish air superiority over US carriers.

Deck Park: These carriers will have a deck park of six A6M2 Zeroes each.

Zuiho and Ryujo.

The light carriers are dedicated to fighter and search operations. The 36 x A6M3 Zeros are shorter ranged models, assigned to defensive CAP. The eight B5N1’s on these carriers are assigned to scouting with a secondary role in level bombing attack with 250kg bombs. The four D4Y1-C Judys are assigned to scouting or pathfinding for fighter control units.
Deck Park: These carriers will have a deck park of three A6M2 Zeroes each.

Chitose, Chiyoda, and Heavy Cruisers

The twenty-eight E13A1 Jakes aboard these ships are assigned to search operations, and to search and rescue. The twenty-four A6M2N Rufes will provide escort for search and rescue E13’s operating near the enemy fleet, as well as to supplement the fleet’s anti-torpedo bomber CAP patrols.

Land Based Elements.

The land based groups are carrier-capable wings assigned to airfields in the Rabaul region. After the main battle the operational IJN carriers will replenish their air wings with the land based units in order to continue operations with minimal pause.

Relative Combat Power of the carrier fleets, (excluding the land-based reserve air units)

Fighters

IJN Fighter Power: 208
USN Fighter Power: 122
(The A6M2, A6M3, and F4F’s are assigned a strength of ‘1’. The A6M2N Rufe is rated at .75.)

Bomber Striking Power

Historical: 3 carriers crippled on 66 Kate attacks (22 aircraft per carrier crippled).
Historical July 1942 allocation (Shokaku and Zuikaku only): 36 Kates = crippling power of 1.63.
Ahistorical – 108 Kates on 2 fleet carriers = cripple power of 4.91

(IJN dive bombers never crippled a US carrier in 1942, therefore are ignored.)

Issues.

Timeframe: Given aviator and aircraft production bottlenecks, I would suppose this reorganization is probably ready for battle by the start of October 1942, two months after the 1st Marine Division lands on Guadalcanal. Therefore, the IJN carrier fleet will seek a decisive battle, not by attacking Henderson Field, but by covering a Japanese invasion of the Santa Cruz Islands. The USN cannot permit this to occur, as IJN possession of them would threaten USN SLOC to Guadalcanal.

Deck Parks: IJN carriers did not usually employ deck parks. In order to achieve fighter superiority in carrier battles, they would need to. The 36 Zeros in the deck parks on the six carriers would launch before dawn for CAP patrols, clearing the flight decks for search and strike operations. The IJN light carriers would launch their scout aircraft before dawn, freeing their flight decks for CAP support afterwards.

Fighter Operations:36 A6M3’s would be assigned to IJN CAP operations, along with some A6M2N Rufes. Of the 154 A6M2 Zeroes, some would be employed in pre-strike air control missions over the US fleet, (using D4Y Judys as pathfinders, while others would be used in defensive CAP operations. This will leave over 80 as escorts for strike aircraft. That level of escort, in conjunction with fighter sweeps, will completely overwhelm the US CAP defenses such as to allow the Zuikaku and Shokaku heavy torpedo bomber groups to punch through and cripple the US carriers.

Search Operations: The IJN cruisers will deploy ahead of the main fleet both to improve the search results of their E13’s as well as to act as ‘bomb sumps’ for US carrier strikes. The E13’s and B5N1’s of the main fleet will also conduct searches such that total numbers and depth of searches will give Nagumo the full tactical picture in time to deliver the full punch of a two-deck torpedo bomber strike.

Rescue: A large number of E13A1’s are assigned to search and rescue operations, to look for downed crews in the water. E13’s with A6M2N Rufe escorts would trail air strikes towards the US fleet in order to be well positioned to rescue airmen in the water near the US fleet, plus to scour waters between the fleets for aircraft that have landed short of the Japanese carriers due to battle damage or fuel exhaustion.

 

[iddt3]

What's the tradeoff? What operations and priorities are they for going by hyper concentrating the carriers?

This also sounds like the IJN needs to be able to freely admit what isn't working optimally, which seems pretty close to ASB.

 

[Sekhmet_D]

Have you considered that this strategy was not implemented because even by then, the JNAF lacked enough pilots to man those planes?

 

[Post]

These required large well trained formations in order to deliver the multiple hits necessary to slow a US carrier enough that IJN surface forces could catch and destroy them.

As @Sekhmet_D noted above, it's going to be a problem to find these well trained formations.

 

[mack8]

Interesting concept, will have a look at it closely. For now i'll say that indeed any land based B5N2s and D3As should be assigned to the carrier force, no point in frittering them away a dozen here a dozen there to land bases.

And also there is still room for the Rikkos force to play a role, i'm thinking organizing them along the lines of the later 1st air fleet of 1943, in a single unit whose main aim is to attack the US carriers. While operational necesities would require Rikko units to be based in NEI, Rabaul, Marshalls etc, for deterrence and search purposes and perhaps harassment day/night strikes against enemy objectives when necessary, the bare minimum should be based there while the rest should be kept in the rear.
When a US carrier force shows up, then the Rikkos are quickly redeployed to the target area, and carry out day and dusk torpedo attacks under heavy fighter escort against the US carriers.

Guadalcanal is a good example how this could have worked imo. Even with the more or less the OTL Rikko organization, if the japanese kept their cool and didn't rush to send weak and piecemeal strikes, and mass at Rabaul and Kavieng as many Rikkos (and Zeros) as possible from NEI, Marshalls etc, throughout the 7th, and then on the 8th unleash them armed with torpedoes, in large day and dusk strikes against Fletcher's carriers, then sinking even one american CV would have worth the no doubt hideous losses, and make the job that much easier for when KB arrives in the battle area and engages the USN.

The Rikkos ca still deliver crushing blows in 1942 because the US carrier force is much weaker for 1942 and most of 1943. As it was the Rikkos managed hits even against the mighty Big Blue Fleet through late 1943 and early 1944, so if in 1942 they manage to attack a US carrier force in good numbers and with a strong fighter escort (for daylight strikes), they are likely to dish out some serious blows.

 

[Popcorn]

What would those carriers have been doing otherwise? What’s the timeline for new American carriers reaching the Pacific?

 

[mack8]

The July 1942 reorganization of naval air forces, not including bi-planes or A5M4 Claudes, was as follows

A question regarding the very interesting table above, are the numbers compiled from niehorster.org, or elsewhere? I'm looking at the NEI units and on the site 21 and 23 Koku Sentais indeed have 108 Rikkos in the TOE, but only 96 Zeros (in the table above there are 156 listed)? What am i missing? Thanks.

 

[CV12Hornet]

What would those carriers have been doing otherwise? What’s the timeline for new American carriers reaching the Pacific?

Shokaku, Zuikaku, and Ryujo were committed to battle in August, losing Ryujo in the process as well as 75 aircraft and 61 aircrew.

In general I’d say Glenn has the right overall idea in husbanding Japanese carrier strength and overall combat power for a heavy blow against the Americans; Japanese efforts to retake Guadalcanal were constantly hampered by their piecemeal commitments and forcing them to wait until October by a longer reorganization should help avoid that.

As for new American carriers, not until 1943.

 

[Sekhmet_D]

Japanese efforts to retake Guadalcanal were constantly hampered by their piecemeal commitments and forcing them to wait until October by a longer reorganization should help avoid that.

As I often like to say, Yamamoto kept husbanding his forces at Guadalcanal for a later decisive battle, but he failed to recognise that Guadalcanal WAS that very decisive battle.

 

[David Floyd]

What prevents the IJN from creating another overly complex plan, continuing to suffer from an intelligence disadvantage and suffering Midway 2.0?

At the very least, 4 US CVs aren’t going down without inflicting at least equivalent losses and gutting IJN airpower, and it’s quite unlikely IMO that all 4 would be committed together and lost. A major Japanese victory might see 2 US CVs sunk, 1 heavily damaged and withdrawing and 1 more that wasn’t committed. In exchange Japan loses at least a couple carriers (a ‘kaku and Ryujo, perhaps) plus has to reconstruct the air groups yet again.

Meanwhile, (hypothetically), a heavily damaged Enterprise undergoes repairs while “USS Robin” joins USS Wasp at Pearl, with USS Essex plus some CVLs right around the corner.

Not sure how this helps Japan, ultimately.

 

[Post]

As I often like to say, Yamamoto kept husbanding his forces at Guadalcanal for a later decisive battle, but he failed to recognise that Guadalcanal WAS that very decisive battle.

No, Midway was. The Japanese failed to see they lost the decisive battle.

What prevents the IJN from creating another overly complex plan, continuing to suffer from an intelligence disadvantage and suffering Midway 2.0?

At the very least, 4 US CVs aren’t going down without inflicting at least equivalent losses and gutting IJN airpower, and it’s quite unlikely IMO that all 4 would be committed together and lost. A major Japanese victory might see 2 US CVs sunk, 1 heavily damaged and withdrawing and 1 more that wasn’t committed. In exchange Japan loses at least a couple carriers (a ‘kaku and Ryujo, perhaps) plus has to reconstruct the air groups yet again.

Meanwhile, (hypothetically), a heavily damaged Enterprise undergoes repairs while “USS Robin” joins USS Wasp at Pearl, with USS Essex plus some CVLs right around the corner.

Not sure how this helps Japan, ultimately.

Indeed. There's no reason the US has to play the game the Japanese wanted to play. US intel in general was very good, so chances are they're going to know the Japanese plans, react according to it, and not fall into a trap.

And as you say it's likely that the Japanese are also going to lose carriers in the battle. At the very least they are going to deplete their airforce, which is basically what happened with the OTL carrieractions in 1941-1942. So the end result is very likely that after this decisive battle the Japanese don't have any carriersforces that are ready for action. Then the next carrierbattle will be TTL's equivalent of the great turkeyshoot. Which will probably occur at about the same time as OTL.

 

[mack8]

The issue of deckparks has been brought in the OP. How many planes did the US carriers usually carried as deckparks, say the Yorktowns, the Essex or Independence classs? I'm trying to figure out how many planes could the IJN carriers carry over their OTL numbers if they had used US style deckparks, and of course if they had the extra planes and pilots.

The british armoured carriers were carrying in 1944 numbers far in excess of their rated capacities, by as much as 20 planes. Would that be a realistic extra figure for say a Shokaku class, instead of 72-75 planes maximum in OTL, with deckparks the figure could be 90-95 planes? And for a Hiryu/Unryu class, instead of 54-57 planes, with deckparks could be as many as 65-70 planes? How about CVLs like Zuiho?

 

[CV12Hornet]

@Glenn239 I do have a concern about the proposed specialized air wings for the Shokakus and Hiyos: specifically, I don’t think the Shokakus can carry enough torpedoes to make the strategy work.

My evidence for this concern is that Taiho was only designed to carry 48 torpedoes; that Taiho had twice the ordnance capacity by weight of the Shokakus; and that judging from Ranger’s experience torpedo stowage was not something you could just swap out with bomb stowage, which makes sense from a geometry perspective.
Source on Taiho’s figures: https://www.armouredcarriers.com/japanese-aircraft-carrier-taiho-armoured-flight-decks

The point being that the Shokakus probably can’t arm those 54 Kates with torpedoes, since they don’t carry enough of them, and so your conception of a massed strike of torpedo bombers from the two carriers isn’t viable. Theoretically more torpedo stowage could be backfitted in, but I suspect that would be a major refit that would take longer than the four months you have the carrier force in reorganization.

 

[Glenn239]

Have you considered that this strategy was not implemented because even by then, the JNAF lacked enough pilots to man those planes?

The IJN had sufficient aircraft and aviators as of May 30th to plan for a carrier establishment of roughly 560 aircraft and aircrews for the summer of 1942. According to Shattered Sword, the Battle of Midway cost the IJN about 25% of its aviators as casualties, or roughly 115 aircrew out of approximately 460 embarked on the four carriers lost. That will have left something like 345 air crew supernumerary to their sunken carriers after the battle. So I think the problem in July 1942 will have been aircraft availability, not air crews. On the air crew front, the defeat at Midway will have actually left the remaining six carriers (and their capacity of about 310 aircraft) over-stocked with available crews I think.

 

[mack8]

Japanese wiki says the Shokakus could carry 45 torpedoes. At any rate, i think such a large numbers of B5Ns is a bit to much to handle effectively, as well as perhaps finding space for them, i would go for 36 (hence more escorts) Zeros and 45 B5Ns, still totaling 90 kankos. Might alleviate a bit the issue of B5N2 availability as well. Junyos then have 36 Zeros and 18 D3As each, and the CVLs with 30 plus 33 Zeros (just to go by multiples of 3 plane shotais) and 6 eachs B5N1s, and i don't think they could operate the D4Y which need to go either on the Junyos or the Shokakus.

 

[steamboy]

There's also the issue with construction as well, would Japanese industry be able to produce enough aircraft of these specific types to carry out this plan.

 

[Glenn239]

A question regarding the very interesting table above, are the numbers compiled from niehorster.org, or elsewhere? I'm looking at the NEI units and on the site 21 and 23 Koku Sentais indeed have 108 Rikkos in the TOE, but only 96 Zeros (in the table above there are 156 listed)? What am i missing? Thanks.

Might be an error on the A6M2 totals in the NEI.

 

[mack8]

Regarding the lack of B5N2s, rather than the underpowered B5N1s, how about using instead the B5M2s? There is a bit of muddy info about it, in some places it's said it was worse than the B5N, but i think japanese wiki says actually pilots found it better than the B5N, presumably the underpowered B5N1. The B5M2 has a 1000HP (or 1070HP?) Kinsei engine, so same power as B5N2, hence presumably similar lifting capability with a torpedo, and speed wise again it's similar to B5N2, so should keep pace.

 

[Glenn239]

Indeed. There's no reason the US has to play the game the Japanese wanted to play. US intel in general was very good, so chances are they're going to know the Japanese plans, react according to it, and not fall into a trap.

The US 1st Marine Division will be on Guadalcanal. The threat that forces Nimitz to commit his carriers would be a Japanese invasion of the Santa Cruz Islands in October 1942. If the Japanese take these, then IJN seaplanes operating from there can coordinate with IJN submarines to attack US supply lines to Guadalcanal, and to assist IJN submarines to go after US carriers operating in support of the Marines. With Santa Cruz in Japanese hands, IJN carrier/surface groups can enter the waters between Guadalcanal and Espiritu Santo via Santa Cruz under the cover of a seaplane search umbrella extending south of Noumea, these IJN incursions risking the severance of Allied sea communications to Guadalcanal.

 

[Glenn239]

Japanese wiki says the Shokakus could carry 45 torpedoes. At any rate, i think such a large numbers of B5Ns is a bit to much to handle effectively, as well as perhaps finding space for them, i would go for 36 (hence more escorts) Zeros and 45 B5Ns, still totaling 90 kankos. Might alleviate a bit the issue of B5N2 availability as well. Junyos then have 36 Zeros and 18 D3As each, and the CVLs with 30 plus 33 Zeros (just to go by multiples of 3 plane shotais) and 6 eachs B5N1s, and i don't think they could operate the D4Y which need to go either on the Junyos or the Shokakus.

A Shokaku could carry 45 torpedoes and 60 x 800kg bombs, plus 312 x 250kg bombs. Each heavy carrier will require 108 torpedoes for the anti-carrier mission, which is 2 rounds for each bomber aboard. There is no requirement for 800kg bombs - the carrier Kate wings are purely torpedo attack units with no anti-land target capabilities. A poster asked on how a Midway style debacle could be avoided. The answer is, the 'kaku Kate groups never carry bombs, so they never have to worry about switching armaments. The Kate crews aboard Shokaku and Zuikaka are not even trained for level bombing after June 1942, they are focused exclusively on torpedo attack. The 'kakus will therefore carry no 800kg bombs, freeing up space in the magazines to carry more torpedoes. This should be enough to reach the required 108 torpedoes stowed.

WRT the 250kg bombs, there is also no requirement for these WRT to the torpedo attack units carried. However, the force does have a land based element of 54 D3A1's intended for deployment aboard Shokaku and Zuikaku. Some 250kg would have to be stowed for that possibility, but not as many as the 312 maximum capacity.