Kido Butai if Pacific war averted in 1941-42

EwenS

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And this happens why?
You beat me to that question.

Look at the background to this.

18 Sept 1931 Mukden Incident. Engineered by the Imperial Japanese Army as a pretext for invasion of Manchuria.
Jan 1932 Stimson Doctrine (from USA) spelled out to Japan and China. No recognition of changes of international borders executed by force.
March 1932 foundation of the puppet state of Manchukuo
15 May 1932 assassination of Japanese Premier by young naval officers.
Sept 1932 the Japanese Government recognises Manchukuo
Oct 1932 Lytton Report to the League of Nations
Feb 1933 League motion naming Japan as the aggressor.
27 March 1933, Japan walks out of the League.
1932-37 various incidents between China & Japan culminating in the 7 July 1937 Marco Polo Bridge incident and full scale war.
1938 onwards, increasingly restrictive sanctions applied by the US and other nations
1941 Tōjō rejects the idea of compromise in China leading to the freezing of Japanese assets and the oil embargo and the final slide to Pearl Harbor.

So why does the USA suddenly decide in 1937 to reverse its previous policy as laid out in the Stimson Doctrine in 1932 and accept Japanese occupation of Manchukuo?

Can the Japanese Government actually regain control of the Imperial Japanese Army in China and cause them to withdraw?

Are the Japanese Govt (as opposed to the IJA) actually willing to make those concessions in 1937?

As for the Japanese carriers, nothing changes. In June 1936 revised Japanese planning was based around a fleet with 10 carriers. Hosho, Akagi, Kaga and Ryujo already in service, Soryu & Hiryu building and planned conversion of the hulls that became Shoho & Zuihō. To that were to be added two new larger ships that were then designed. These were Shokaku & Zuikaku laid down in Dec 1937 and May 1938 respectively.

1929/30 also saw the start of the Japanese programme to subsidise the construction of merchant shipping suitable for conversion to carriers in the event of war. More were added in 1937, 1938 and 1939. And suitable hulls for conversion were also available in the form of Chitose (laid down 11/34), Chiyoda (l/d 12/36) and Taigei (l/d 4/33 & converted as Ryūhō).

Of the Japanese WW2 carriers, that only leaves Taiho, for which design planning began in 1939 although she was not finally laid down until July 1941, Shinyo, converted from the German liner Scharnhorst stranded in Japan on the outbreak of war, Shinano and the Unryu class from the wartime programmes.

So the majority of the elements for the main Japanese carrier fleet, and plans for the shadow carrier fleet, were in place by the end of 1936.

The only remaining question is when would the IJN get round to forming the Kido Butai itself. Historically this did not occur until 10 April 1941, only 8 months before Pearl Harbor.
 

Admiral Beez

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They're swamped by 24 Essex class CV's from the 1940 building program?
If a negotiated settlement can be made on Manchukuo in 1937, this is before Japan invades greater China and Japan’s dramatic increase in military spending. It’s also before the IJA’s generals took over government, with the civilian Hirota as PM.

Getting back on topic of IJN aviation, in addition to being two or three years before the Essex program, we’re also before the launch of the A6M, Aichi D3A, Shōkaku and Hiyō programs. If Japan maintains lower military spending, does the isolationist US Congress still authorize massive expansion of its carrier fleet, or focus more on potential troubles in Europe and the Atlantic? Regarding the main topic of the IJN carrier force, I’m thinking that the smaller ships like Hōshō and Ryūhō would be replaced by whatever becomes the Shōkaku program.
 
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EwenS

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They're swamped by 24 Essex class CV's from the 1940 building program?
There were only 11 Essex in the 1940 Programme (CV-9 to CV-19) ordered July-Sept 1940 and scheduled for completion between April 1944 and April 1946.

Two more were added in Dec 1941, 10 in Aug 1942 (8 completed to original configuration + Oriskany in 1950) as part of the maximum war programme, 3 in June 1943 (2 completed) and 6 planned in 1945 (none laid down)
 

Admiral Beez

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No war in the Pacific would have meant continued action in China and war with Russia when German invaded.
If a diplomatic settlement can be had with Britain and the US, do you still see Japan getting cozy with Germany after 1938? I can’t see the utility of such an arrangement, as it would antagonize a now placated Britain.

If a neutral Japan can last until late 1942 when Germany has clearly lost the plot in Russia, they’ll be thanking their tea leaves that they didn’t side with Germany. Also, with no PH, does Germany declare war on the US? If the US remains neutral into 1942, I can see Japan eventually allying herself with Britain and Russia, on a limited scale, if only for the spoils.
 

EwenS

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If a negotiated settlement can be made on Manchukuo in 1937, this is before Japan invades greater China and Japan’s dramatic increase in military spending. It’s also before the IJA’s generals took over government, with the civilian Hirota as PM.

Getting back on topic of IJN aviation, in addition to being two or three years before the Essex program, we’re also before the launch of the A6M, Aichi D3A, Shōkaku and Hiyō programs. If Japan maintains lower military spending, does the isolationist US Congress still authorize massive expansion of its carrier fleet, or focus more on potential troubles in Europe and the Atlantic? Regarding the main topic of the IJN carrier force, I’m thinking that the smaller, older ships like Hōshō and Ryūhō would be replaced by whatever becomes the Shōkaku program.
The Japanese decision to aim for a 10 carrier fleet dates to June 1936 (i.e. a whole year before all the troubles blew up in China in July 1937) and were based on how Japan saw the needs of defending its Empire. Having come to that conclusion and set out on the course to completing that plan by building the Shokaku pair, why should they suddenly change tack and decide a smaller carrier fleet is appropriate.

After all they couldn’t be certain that war would not happen at some point. They didn’t know in 1936 or even 1937 that things would end up in war at the end of 1941. They did know that they couldn’t outbuild the USA during a war, especially in Battleships, so needed to start their carrier programme early to give themselves, another option, just in case.

As for the US carrier plan, 1938 saw Congress provide funding for 2 new carriers with a combined tonnage of 40,000 tons (Second Vinson Act). One became CV-8 Hornet. The balance was carried forward into the 1940 Essex Programme. But even if that had been followed through the Japanese would have had a 10 - 8 advantage come 1941/42.

The 1940 US expansion is triggered by events in Europe not the Pacific. It is the prospect of fighting in both oceans that causes it. Peace with Japan = less need for such a large expansion, unless it is treated simply as a modernisation of the existing fleet, replacing the old with the new.
 

EwenS

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I thought the IJN has fuel for only 6 more months before the start of the war. 🤔
It wasn’t quite that bad. Somewhere between 1-2 years without substantial imports from DEI.

But the OP is proposing no oil embargo until some point way beyond the historical 1 Aug 1941. California was Japan’s largest oil supplier in 1941 and worse, most of that was being moved in US tankers.

There is a study here of Japan’s oil position before and during WW2 if you are interested in some more detail.
 
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Admiral Beez

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I thought the IJN has fuel for only 6 more months before the start of the war. 🤔
That's in 1941, certainly. But in 1937 the worst of the sanctions and embargos were still years away. It was only after Japan's invasion of China in summer 1937 that the US, Britain and Dutch began to tighten the screws. If however the Japan can achieve US and European power recognition of Manchukuo, as Australian was pushing Britain to do so, Japan's government might not have returned to IJA rule and Japan might not invade China in 1937-38. That's a lot of what-ifs, but recognition of Manchukuo would be a major fork in the road. And British recognition wasn't a fanciful long shot, but a real possibility that would have implications, including for the IJN's naval aviation.
 

Shinpachi

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If Britain and the USA recognize Manchukuo in 1937 and drop the oil/trade sanctions in exchange for Japan retreating from the rest of China and averting/delaying war past 1942, what happens to the IJN's carrier fleet.
Under such a condition, Japan has no reason to make war with the Allies. IJN will concentrate on its power expantion to take balance with USN. Also looks a good chance to negotiate and purchase oil from the Dutch East Indies if they are pleased to.
 

GrauGeist

Generalfeldmarschall zur Luftschiff Abteilung
If Khalkin Gol still happens in 1939, with the same outcome, Japan again ends up with no desire to tangle with the Soviets.
But if Japan is not going to war with the U.S. in 1941, then they could turn their attention to the Soviet Union in support of Germany's invasion.

Historically, they used the non-aggression pact with the USSR to their advantage by not having to focus on defenses in their west coast and in the region between the home islands and Asia proper.
 

vikingBerserker

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I agree, this time Russian forces are being sapped by the Eastern Front which leaves the Soviet East with their raw materials wide open. For Russia the main front will be with Germany and they will trade space with Japan for time. The question for Soviet survival is if the Allied Lend-Lease program still happens. The only downside I can see for Japan is their extremely strong Navy. They will not be able to fully utilize in a landlocked war, though the Navy aircraft could participate.
 

Thumpalumpacus

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It wasn’t quite that bad. Somewhere between 1-2 years without substantial imports from DEI.

That's my recollection. I believe it was John Toland in The Rising Sun who cited the IJN having oil stocks for eighteen months of operations without securing any other supplier after the July embargo by America.
 

Admiral Beez

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With immediate war averted and Japan running on a peacetime economy, I would see the IJN rationalized, with smaller CVs disposed of and PH-era liner-conversions (Hiyō, Jun'yō, Ryūjō, etc.) never built, and instead focused on new builds.

Hōshō and Ryūjō scrapped
Kaga and Akagi converted to full deck (same as historical), but to be later deleted and replaced by two Taihō class
Sōryū/Hiryū program expanded with two additional units to replace Hōshō and Ryūjō
Shōkaku/Zuikaku program expanded, with two additional units to replace Hiyō and Jun'yō

This will give Japan ten fast fleet carriers. Further rationalization of the battlefleet will be needed. I'm not sure what to do with the first of five planned Yamato class then (by 1937) laid down. Maybe skip the lot, make the first, Yamato into an aircraft carrier or cancel the program. Focus on aviation, submarines and cruisers.

After which I'd have Japan look to reenter the naval treaties with London and Washington.
 
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