What if Japan avoided attacking Pearl Harbour?

Still, isolationism was a major force even in 1941 America, while the American ...

It was a dead force, a dead man walking. The collapse of France created a major sea change in the core attitudes of the US population. The lack of effective opposition to the War Powers Acts of 1940, the mobilization of the US military, and the extention/expansion a year later illustrates part of that trend.
 
Once the oil embargo became complete the clock was ticking for Japan. They had roughly 18 months of petroleum to run a war and their civilian economy. Production in Japanese controlled territory before 1942 was minimal. The banking systems had cut them out of the Sterling and Dollar zones so they could only use cash (hard currency or physical gold) to make purchases anywhere outside of the Yen zone - this meant even if they could buy oil from Persia or Arabia (controlled by UK/Dutch/US companies) they did not have the tanker resources to bring much to Japan given the round trip time and the capacity of any one tanker. The point of the oil embargo and the materials embargo for minerals etc was to put Japan in a position of find an end to the war in China or see everything come to a screeching halt in a couple of years.

The US islands in the Pacific and in particular the Philippines meant that even if Japan seized SEA the sea lanes to/from Japan could be interdicted at will, negating the value of the conquests. On top of that the Japanese knew that the defenses in the PI and Wake were being built up and that the US was rearming rapidly, especially the navy. They had a binary choice, a "peace" in China that was not complete control by them or war with the USA so the war with China could continue - period. All other options had been exhausted. They chose poorly.

Isolationism was not pacifism or disarmament. It was more about NOT getting involved in another European mess and being screwed financially and ignored by a peace that solved nothing - the isolationist view of WWI. Protecting the western hemisphere, especially with a navy and air corps build up was quite OK, the army build up was a little more problematic as a larger army was not as important for protection for the US/western hemisphere as a navy and air corps. In the Pacific, racism joined with politics to keep the Japanese well away from the US west coast. Remember there had been specific oriental/Japanese exclusion laws at the behest of west coast legislators since the late 19th surgery. In any case once you have US territory occupied by the Japanese, Americans killed by the Japanese it is, to use an old phrase "war to the knife and the knife to the hilt." In addition to his prediction that Japan would run wild for up to a year no more, Yamamoto also said that the only way the Japanese would get the gains they wanted would be by dictating the peace in the White House.
 
If Americans die at Pearl Harbour = War.

If Americans die in combat with Japanese (after Congress has ratified a Declaration of War, mind) = meek surrender.

I seriously can not see a surrender. I can see the Pacific getting even less attention the in OTL while still building ships and
supplies to get back at Japan. There would be minor incidents but less then in OTL. Unless Japan is dumber then OTL, they may be, they
will leave the US alone in the Pacific. Europe may end earlier but remember Trinity was built for the Germans not Japan. Giving the Pacific war
our full attention we might start with wiping 6-8 cities off the map. Japan still can't build enough ships or planes compared to the US in 2-3
years or even if it takes 5 They atrocities they committed would be front page news and American's would be pissed. The Holocaust would rub off on Japan
even though it wasn't exactly like Germany's but they were allies. I doubt Japan would have gotten the good treatment they did in OTL but much more harsh.
 
If memory serves the oil production in DEI is not overwhelmingly impressive. Synthetic oil/fuel technology would be usable but the infrastructure needed would be significant. If that were dispersed and functional in a 2-3 year timeframe there might be a solution. Despite this the Phillippines will remain a 'location of interest' for Japan. I expect as others here do that the US would go into the war within 6-9 months but given Kimmel's thinking about a grand battle and the American torpedo situation at the time this might turn into a disastrous rout early in the war and fuel isolationist sentiment. Regardless I think it stretches out the war by 6-12 months, especially if Japan coordinates with Germany more and likely breaks deeper into the Raj. There is also a small chance that, without US involvement, China capitulates and Japan has a real shot at taking a lot of Asia south of the USSR.
 

CalBear

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But that's not realistic in itself, the Japanese knew they were going to be fighting the Americans sooner or later. They chose to do it sooner, in the hope they could knock the Americans out on their terms.
The Japanese also hit the U.S. while they had a reasonable chance of success. They had read the Two Oceans Navy Act and were able to do the math as far as the changes coming.

As an example between 1921 and the end of WW II the Japanese commissioned two battleships (granted they were BIG BB) and had a third under construction prior to converting it to a utility carrier design. The U.S. commissioned four South Dakota class BB between March 20 and August 16, 1942, having commissioned two BB in March-April 1941, and had eleven more fast BB ordered for delivery between March of 1943 and March of 1946 (six Iowa and five Montana class). That would have been a 17:3 ratio. Carriers were worse, while cruiser and destroyers building plans were simply overwhelming.

The Japanese had a very narrow window of opportunity and they chose, very poorly, to take advantage of it.

To the OP: The Japanese had no choice but to attack Pearl Harbor. The U.S., particularly the U.S. Pacific Fleet, presented an existential threat once Japan chose to attack South into the DEI. Military planning requires threat assessment. Once a threat is determined it has to be honored, i.e. taken out of the scenario either by diplomatic means or military action. The Japanese could not leave the Philippines, with its major U.S. air and naval bases, in hostile hands if the resources from the DEI and SEA were to be transported to Japan. American B-17s from the Philippines could interdict all of the South China Sea AND threaten Japanese bases on Formosa. American bases on Guam could threaten the Japanese position on Saipan (which was a LoN Mandate to Japan but one that the Japanese fully intended to retain permanently) while Wake, which was being developed into a B-17 capable base, provided a perfect location to attack Japanese positions in the Marshalls (another Lon Mandate that Japan considered to their permanent territory).
 
CalBear:

I think an attack on Pearl would be extremely likely barring major butterflies but the timing might vary substantially. Given the attitudes of the day it was thought inconcievable by many that the Japanese would be capable of planning - much less executing - a strike of that scale and catch the US so woefully ill-prepared. Yet to strike earlier means the attack is likely less effective, to strike later means the base might be better prepared. A strike with the A6M3 model 22 instead of A6M2 model 21 might also be feasible if done late enough but could be countered by early F4Fs instead of P-39s and similar.
 

CalBear

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CalBear:

I think an attack on Pearl would be extremely likely barring major butterflies but the timing might vary substantially. Given the attitudes of the day it was thought inconcievable by many that the Japanese would be capable of planning - much less executing - a strike of that scale and catch the US so woefully ill-prepared. Yet to strike earlier means the attack is likely less effective, to strike later means the base might be better prepared. A strike with the A6M3 model 22 instead of A6M2 model 21 might also be feasible if done late enough but could be countered by early F4Fs instead of P-39s and similar.
The Japanese moved, almost literally, as soon as the six fleet carriers called for in the plan were available. Zuikaku completed her shakedown cruise/builder's trials on November 5th 1941. Her air wing, which was supplemented from aircraft/aircrew being used for instruction, as well as new construction to the point that the paint was still tacky on the wings, were loaded on November 19th. The Kido Butai left for the Pearl Harbor Raid on November 26th. Three weeks after the sixth deck required for the attack was available the IJN sortied.

Every day the Japanese wait, the U.S. gets stronger. As I noted earlier the U.S. commissioned four fast BB between March and August of 1942 (IOTL one of them was in combat by October of '42). One of my favorite coincidences of the War is that Leroy Grumman scheduled a "grand opening for the new TBF factory in Long Beach at the same time that the Kido Butai's second wave was trapping after the strike (December 7, 1941 at 13:00 Pacific Time). The party was somewhat more subdued than expected. In less than six months that factory was putting Avengers into squadron service.

The Japanese had a window where they could claim a slight superiority that opened in early October of 1941 and was going to end by May of 1942.
 
Attacking Pearl Harbor appears logical to us. But Yamamoto had to move heaven and earth to get the Japanese High Command to approve it. He even to threaten to resign to get his way. Suppose the High Command told him to go ahead and resign. He resigns and the person taking over would know that attacking Pearl Harbor is off the books. Remember just because we see Pearl Harbor attack as the best choice that does not mean the people in the High Command of the Japanese Imperial Navy would look at it that way.

Eri Hotta book Japan 1941 wrote that the leadership of Japan realized that they would probably lose the war but they went ahead with the plans to attack the United States despite the reality of almost defeat. So war was inevitable but the attack on Pearl Harbor was not.
 
One of my favorite coincidences of the War is that Leroy Grumman scheduled a "grand opening for the new TBF factory in Long Beach at the same time that the Kido Butai's second wave was trapping after the strike (December 7, 1941 at 13:00 Pacific Time).
That should have been a target.

Makes me wonder, if the Pacific fleet was based at San Diego in Oct-Dec 1941, what would Japan have attacked?
 

nbcman

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That should have been a target.

Makes me wonder, if the Pacific fleet was based at San Diego in Oct-Dec 1941, what would Japan have attacked?
Maybe the KB would be used to support the Malayan and Philippine attacks or kept in reserve to attack if the USN tried to sail to through their Mandate islands.
 
Maybe the KB would be used to support the Malayan and Philippine attacks or kept in reserve to attack if the USN tried to sail to through their Mandate islands.
Without the element of preemptive surprise, the IJN will be in trouble from day one.
 

nbcman

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Without the element of preemptive surprise, the IJN will be in trouble from day one.
Agreed but the major USN and RN assets are out of their reach The IJN could hit the lighter vessels in the US Asiatic fleet but those ships were considered pretty much unsupportable and expendable IOTL. No matter what the IJN could do, they were in trouble when IJ decided to attack.
 
That should have been a target.

Makes me wonder, if the Pacific fleet was based at San Diego in Oct-Dec 1941, what would Japan have attacked?

The Kido Butai barely had the range to attack Pearl Harbor. They certainly wouldn't have the range to make it all the way to CONUS and back, especially if they were harrassed or damaged at all during that time.
 
Getting within range of Pearl Harbor required a certain amount of luck on the part of the Japanese, in spite of taking a route well out of normal trade routes. Getting to within range of San Diego would have required the intervention of Skippy the ASB due to merchant traffic, naval patrols, and air patrols. Getting away would have been very difficult, and the Japanese were not planning on making this a suicide run. On top of that, Getting enough tankers to refuel the KB there and back, making rendezvous with tankers etc would be doubtful.
 
Getting within range of Pearl Harbor required a certain amount of luck on the part of the Japanese, in spite of taking a route well out of normal trade routes. Getting to within range of San Diego would have required the intervention of Skippy the ASB due to merchant traffic, naval patrols, and air patrols. Getting away would have been very difficult, and the Japanese were not planning on making this a suicide run. On top of that, Getting enough tankers to refuel the KB there and back, making rendezvous with tankers etc would be doubtful.
That's the challenge then, if the USPACFLT isn't at PH, what do they attack?
 

CalBear

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That should have been a target.

Makes me wonder, if the Pacific fleet was based at San Diego in Oct-Dec 1941, what would Japan have attacked?

More firepower against the PI, Wake, and/or in the DEI. A couple decks would have been kept in Home Waters.
Getting within range of Pearl Harbor required a certain amount of luck on the part of the Japanese, in spite of taking a route well out of normal trade routes. Getting to within range of San Diego would have required the intervention of Skippy the ASB due to merchant traffic, naval patrols, and air patrols. Getting away would have been very difficult, and the Japanese were not planning on making this a suicide run. On top of that, Getting enough tankers to refuel the KB there and back, making rendezvous with tankers etc would be doubtful.
Closer to impossible. As I have mention here in the past, the IJN had to DECK LOAD fuel drums on most of the surface escorts (and even deck loaded fuel drums onto the Akagi) to keep their destroyers fueled. Coming all the way to the West Coast was, if not logistically impossible, close enough for government work. The range to Pearl was ~8,800 miles round trip. San Diego (and this is the direct route, no dog legs to avoid shipping lanes) is 11,000+ miles.

Not going to happen.
 
The hits against the PI may be stronger, Guam and Wake will probably go as OTL. There might be a smaller PH hit depending on how much is there. If possible, the schedule/forces for the DEI/Malaya might be beefed up and accelerated. Hitting CONUS is simply not doable - although the Japanese might decide to deploy submarines all the way to the west coast, they certainly had some with the range. Other than that I don't know, the reality is even if the ships that were sunk at PH get sunk in deep water in some Mahanian battle with the Japanese, with higher personnel losses than OTL it really won't matter - and the Japanese will take some hits in this battle as well and the US production lines are humming.
 
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