Japan First

[VirginiaHistoryTeacher]

Consider the effects of Roosevelt deciding to attack Japan first instead of Germany.

I believe this was an easier "sell" to the American public for several reasons.

1) Pearl Harbor. The biggest reason of all, to be sure, but look at the emotional impact of this. U-Boat warfare against shipping in the Atlantic doesn't carry nearly the same weight as bombs hitting American territory and slaughtering American personnel. Nazi aircraft carriers never got close enough to American shores to drop bombs on major harbors.

2) The Bataan Death March. Thousands of American soldiers literally marched, beaten, tortured, starved, etc to death at the hands of their captors. Not to mention the fact that the Philippines were in American hands, making it technically American territory as well. Nazis didn't face American soldiers in any kind of force until the landings in North Africa in May of 1942.

3) Attacks on other American possessions. Guam Island and Wake Island come to mind here.

About when do you think the Empire of Japan would be defeated in a situation where we threw more against Japan than against the Nazis? What sort of long-term effects would this create globally? Looking for more than just "Soviet troops enter Paris by Christmas of 45."

 

[jsb]

- How do you go Japan first without the new ships (Essex class etc) that are still building (and without fixing the ships at PH) ?

-Germany is economically much bigger (and linked with Italy) so is the much bigger threat.

- Why would the Germans (AH would insist on it) Not send everything east to defend Berlin ? (So it always ends up with the army's meeting in mid Germany)

 

[Emperor Norton I]

Would the US even do lend lease to the Soviets?

 

[zoomar]

Consider the effects of Roosevelt deciding to attack Japan first instead of Germany.

I believe this was an easier "sell" to the American public for several reasons

Of course it would have been an easier sell to the American public, but for the US to have adopted a "Japan first policy" it would be essential that Germany not declare war on the US. If somehow, Hitler inexplicably reacted to the Pearl Harbor attack by expressing shock and dismay at the perfidy of his Japanese friends rather than declaring war on the US, that would complicate a Germany first approach. This probably would not substantially shorten the Pacific War, however. The US was very short-handed in 1942, so it is reasonable to presume that the most engagements until early 1943 would play out pretty much as OTL.

Also, its worth noting that a "Germany First" strategy required a different mix of weaponry than "Japan first". To fight Germany initially you needed anti-submarine warfare, a large and modern army with abundant armored vehicles and logistics, and high-altitude strategic bombers. To fight Japan initially, you needed submarines, aircraft carriers and naval aircraft, tactical fighters, gobs of cruisers and other surface combatants, and marines. Also, in the ETO, Britain and the USSR was coming with their a-games. In the PTO, Britain was decidedly a secondary player and the USSR non-existent.

 

[takerma]

Hitler does not declare war on US and this is quite possible.

Japan falls in 1944, home islands invasion will be very costly without a bomb but it will get done.

No D-day. Stalin in Paris. UK will not able to pull of invasion of mainland alone.

In Asia maybe Americans can take control of China and Korea if Stalin is focused on subjugating Europe?

I remember reading a book that had premise like that I think.

 

[Carl Schwamberger]

First off I'd point out that the defeat of Japan & Germany were near simultaneous, their surenders being just four months apart. If you consider WWII as starting in September 1939 thats four of 72 months or 5.6% difference in months.

- How do you go Japan first without the new ships (Essex class etc) that are still building (and without fixing the ships at PH) ?

Aside from the 20 odd aircraft carriers & similar number of escort carriers, there were a large number of specialized amphibious ships, & fleet support ships, to build. Attacking across the Pacific required unique fleet train to be constructed, which took until the autum of 1943 to have ready for supporting a single corps size amphib operation. what should the US do in the meanwhile? Conduct secondary operations in the South Pacific? Patrol the western Atlantic? Send material to the USSR & Britain?

Aside from the extended wait defeating Japan only required 20% to 25% of the resources of the US. Adding more was not going tho accelerate the defeat of Japan by more than a few months. The necessary support fleet had to be built first. Meanwhile the balance of the resources of the US sit idle waiting for the realtively smaller portion to get to its business.

Germany is economically much bigger (and linked with Italy) so is the much bigger threat.
...

And can do more damage in the longer run.

 

[Carl Schwamberger]

Consider the effects of Roosevelt deciding to attack Japan first instead of Germany.

I believe this was an easier "sell" to the American public for several reasons.

The Germany first policy was based on extensive calculation of resource allocation, and threat. This calculation involved many senior Army and Navy officers, Executive branch staff, civilian advisors, and assorted congressmen. deciding against a course of action that had been throughly calculated and recheck at multiple levels would not be supported by very many leaders or voters.

1) Pearl Harbor. The biggest reason of all, to be sure, but look at the emotional impact of this. U-Boat warfare against shipping in the Atlantic doesn't carry nearly the same weight as bombs hitting American territory and slaughtering American personnel. Nazi aircraft carriers never got close enough to American shores to drop bombs on major harbors.

German submarines had previously sunk US cargo ships and warships. The public became increasingly outraged. After the Japanese attack the German operation Drumbeat off the US coast sank more ship, more tonnage, and killed nearly as many Americans as the Japanese did at Pearl Harbor, in just a couple months. The US public was also aware of German spy and sabatouer teams being landed on the US coast.

2) The Bataan Death March. ...

The general fact was not know to the US intellgence services or the US leaders and public for months. Not until mid 1942 did the fact of the event become known. Confirmation and details did not become understood until the 1944 capture of Luzon. When the decision for Germany first was made the Battan Death March was just one on many distorted and ot understood rumors.

3) Attacks on other American possessions. Guam Island and Wake Island come to mind here.

...and German special forces teams were being landed on the US East coast & ships were being sunk daily, most in sight of the coastal population.

About when do you think the Empire of Japan would be defeated in a situation where we threw more against Japan than against the Nazis?

My best guess is a few months earlier. Maybe. Japans decision to surrender was influenced by four factors:

1. Destruction of the Japanese Navy

2. Report of the failure of the 1945 rice harvest & certainity of mass starvation the next winter.

3. The Soviet declaration of war.

4. The second atomic bomb

Number one could have been accelerated a few months. Two could not be accelerated by conceivable US action. Three, the Soviet DoW was contingent on Germany surrendering. Any delay in German surrender delays the Soviet DoW. Four, it is difficult to see the deployment of the atomic weapons occuring more than a few weeks faster.

What sort of long-term effects would this create globally?

More dead in Europe, Not only from the contnuing combat, but less time to prepare for the winter of 1945-46. The extreme poverty of post war Europe killed a lot of malnourished & exposed civilians during the next two winters. Every week of delayed peace and reduce preparation means another ten or twenty thousand deaths. Conversely Japan surrendering a couple months earlier means more survivors on that side of the planet.

One final note. the Europe First strategy was not effectively implemented until the commitment to Operation Gymnast/Torch in mid 1942. Until then the US reources allocated to each side of the globe varied from near even to weighted to the Pacific. ie: In November 1941 175 B17 bombers were in the Phillipines & approx 400 were to be there by February. Far less had been planned for British use in those same months. ie: The best & most experienced US aircraft carriers wer eallocated to the Pacifc. The Atlantic was assigned less capable carriers like the Ranger, or new ships that were still working up.

 

[jmc247]

The Germany first policy was based on extensive calculation of resource allocation, and threat. This calculation involved many senior Army and Navy officers, Executive branch staff, civilian advisors, and assorted congressmen. deciding against a course of action that had been throughly calculated and recheck at multiple levels would not be supported by very many leaders or voters.

The U.S. public was against Germany first, even a great many Congressmen were against it hence FDR locking up the Japanese to appease public opinion that were far more angry and afraid of Japan then Germany before the election.

If war with Germany starts say mid 1942 over some LL ship sinking the politics will be all the harder for Germany first and the gears of war will already be in place for a Japan first strategy and then to ease into the European war.

The war in Europe still ends pretty much on time because if anything with Germany doing a bit better in Europe there will be more effort from the government and the scientists involved and more of a rush on the Manhattan Project so nukes possibility ready at or near the time V-E Day happened OTL.

 

[Look More Closely Later]

British political morale

Consider the effects of Roosevelt deciding to attack Japan first instead of Germany.

I believe this was an easier "sell" to the American public for several reasons.

1) Pearl Harbor. The biggest reason of all, to be sure, but look at the emotional impact of this. U-Boat warfare against shipping in the Atlantic doesn't carry nearly the same weight as bombs hitting American territory and slaughtering American personnel. Nazi aircraft carriers never got close enough to American shores to drop bombs on major harbors.

2) The Bataan Death March. Thousands of American soldiers literally marched, beaten, tortured, starved, etc to death at the hands of their captors. Not to mention the fact that the Philippines were in American hands, making it technically American territory as well. Nazis didn't face American soldiers in any kind of force until the landings in North Africa in May of 1942.

3) Attacks on other American possessions. Guam Island and Wake Island come to mind here.

About when do you think the Empire of Japan would be defeated in a situation where we threw more against Japan than against the Nazis? What sort of long-term effects would this create globally? Looking for more than just "Soviet troops enter Paris by Christmas of 45."

Does the USA want the UK to carry on fighting? If so, given the really bad start that the UK had in the original timeline to 1942, it would be tremendously helpful to Churchill if the USA announces 'Germany first', even if it has its fingers secretly crossed behind its back, and then spends 1942 messing around in the Pacific playing 'Battleship' with the Japanese. Churchill able to say to the UK parliament 'the USA are on our side, and say "Germany first"' is in a rather different position to a Churchill humiliated by an announced "Japan first" strategy. In the latter scenario, the UK parliament might decide to remove Churchill and get the best deal it can out of Hitler. (As it was, Churchill had to fend off *two* attempts to remove him from office in the first six months of 1942, prompted by various events in the Far East and North Africa.)
Churchill isn't a dictator or a head of state with an unlimited term or even a fixed term in office. He can be removed by a vote of 'no confidence' by the British parliament at any time.

 

[takerma]

Would it no help to get more aircraft, equipment etc for Guadalcanal, Midway etc?

With whole production crunching out carriers, aircraft and support vessels. Would it not be possible to win by 1944?

If Hitler does not declare war and boats are not sinking everything in sight by the coast. Selling war in Germany over Japan is going to be really hard.

 

[Lee-Sensei]

Consider the effects of Roosevelt deciding to attack Japan first instead of Germany.

I believe this was an easier "sell" to the American public for several reasons.

1) Pearl Harbor. The biggest reason of all, to be sure, but look at the emotional impact of this. U-Boat warfare against shipping in the Atlantic doesn't carry nearly the same weight as bombs hitting American territory and slaughtering American personnel. Nazi aircraft carriers never got close enough to American shores to drop bombs on major harbors.

2) The Bataan Death March. Thousands of American soldiers literally marched, beaten, tortured, starved, etc to death at the hands of their captors. Not to mention the fact that the Philippines were in American hands, making it technically American territory as well. Nazis didn't face American soldiers in any kind of force until the landings in North Africa in May of 1942.

3) Attacks on other American possessions. Guam Island and Wake Island come to mind here.

About when do you think the Empire of Japan would be defeated in a situation where we threw more against Japan than against the Nazis? What sort of long-term effects would this create globally? Looking for more than just "Soviet troops enter Paris by Christmas of 45."

IIRC, despite the Germany first policy the Americans were putting more into the war with Japan until Operation Overlord.

 

[David T]

Hitler does not declare war on US and this is quite possible.

And will make no difference to the Germany-first strategy. To quote an old post of mine at https://www.alternatehistory.com/discussion/showpost.php?p=9879227&postcount=14

***

IMO the difference is more likely to be days than weeks. As I have noted before, FDR's December 9 radio address to the nation certainly sounds like a rehearsal for a proposal to declare war on Germany [1]--and it is possible that if FDR did not yet ask for a declaration at that time, it may have been because he was convinced from intelligence sources and decrypts that Germany would soon declare war on the US.

And as I have also noted, with regard to how hard a time FDR have had in getting a declaration of war through Congress, I think a Gallup poll from December 10, 1941 should settle that: " The December 10, 1941, Gallup/AIPO (American Institute of Public Opinion) poll asked. "Should President Roosevelt have asked Congress to declare war on Germany, as well as on Japan?": yes — 90%, no — 7%." http://books.google.com/books?id=61WMf6XRVT8C&pg=PA209

The general reaction in the US press--including the former isolationist press--to the German DoW was incidentaly one of indifference. It was a mere formality, they said; the US and Germany were already really at war, Japan could not have pulled off Pearl Harbor without German inspiration, etc.

There is also incidentally no reason to think that if the US rather than Germany had declared war first it would have made any difference to the "Germany first" strategy which US planners had agreed on well before Pearl Harbor. As Louis Morton writes, by the summer of 1941,

"...the decision on the course the United States would follow in the event it was "compelled to resort to war" had, in effect, been made. The United States would make the main effort in the Atlantic and European area where the major enemy, Germany, was located, Just how the final blow would be delivered was not yet known, but the Americans expected it would require a large-scale ground offensive. In the Pacific and Far East, United States strategy would be defensive, with greatest emphasis on the area encompassed by the strategic triangle, Alaska-Hawaii-Panama. Implicit in this concept was acceptance of the loss of the Philippines, Wake, and Guam, Thus, in a period of less than three years, the Pacific orientation of U.S. strategy, developed over a period of many years, was completely reversed. By mid-1941, in response to the threat from Europe, the eyes of American strategists were focused on the Atlantic. It was there, they believed, that the war in which the United States was certain to be involved would be decided.

"These expectations were more than fulfilled. Though the war when it came opened with an attack in the Pacific, the President and his military advisers made it clear at the outset in the first of the wartime conferences with the British held at Washington in December 1941-January 1942 (ARCADIA) that they would stand by their decision to defeat Germany first. Not once during the course of the war was this decision successfully challenged." http://www.history.army.mil/books/70-7_01.htm


***
[1] The course that Japan has followed for the past 10 years in Asia has paralleled the course of Hitler and Mussolini in Europe and Africa. Today, it has become far more than a parallel. It is collaboration so well calculated that all the continents of the world, and all the oceans, are now considered by the Axis strategists as one gigantic battlefield.

In 1931, Japan invaded Manchukuo without warning.

In 1935, Italy invaded Ethiopia without warning.

In 1938, Hitler occupied Austria without warning.

In 1939, Hitler invaded Czechoslovakia without warning.

Later in 1939, Hitler invaded Poland without warning.

In 1940, Hitler invaded Norway, Denmark, Holland, Belgium, and Luxembourg without warning.

In 1940, Italy attacked France and later Greece without warning.

In 1941, the Axis Powers attacked Jugoslavia and Greece and they dominated the Balkans without warning.

In 1941, Hitler invaded Russia without warning.

And now Japan has attacked Malaya and Thailand and the United States without warning.

It is all of one pattern...

Your Government knows that for weeks Germany has been telling Japan that if Japan did not attack the United States, Japan would not share in dividing the spoils with Germany when peace came. She was promised by Germany that if she came in she would receive the complete and perpetual control of the whole of the Pacific area and that means not only the Far East, not only all of the islands in the Pacific, but also a stranglehold on the west coast of North, Central, and South America.

We also know that Germany and Japan are conducting their military and naval operations in accordance with a joint plan. That plan considers all peoples and nations which are not helping the Axis Powers as common enemies of each and every one of the Axis Powers.

That is their simple and obvious grand strategy. That is why the American people must realize that it can be matched only with similar grand strategy. We must realize, for example, that Japanese successes against the United States in the Pacific are helpful to German operations in Libya; that any German success against the Caucasus is inevitably an assistance to Japan in her operations against the Dutch East Indies; that a German attack against Algiers or Morocco opens the way to a German attack against South America.

On the other side of the picture we must learn to know that guerrilla warfare against the Germans in Serbia helps us; that a successful Russian offensive against the Germans helps us; and that British successes on land or sea in any part of the world strengthen our hands.

Remember always that Germany and Italy, regardless of any formal declaration of war, consider themselves at war with the United States at this moment just as much as they consider themselves at war with Britain and Russia. And Germany puts all the other republics of the Americas into the category of enemies. The people of the hemisphere can be honored by that.

http://avalon.law.yale.edu/wwii/dec06.asp

 

[VirginiaHistoryTeacher]

Fair enough.

Let's assume some other things. Mix this up a bit.

Let's assume that the United States decides to go rabidly isolationist in terms of European involvement after World War I. This policy sticks through the interwar period. Here are 53,000+ American boys coming home in coffins. All have died largely in vain with Hitler's rise to power. Europe is literally on its own. (My own personal opinion is that Britain can and will endure this, probably the Soviets too just with sheer numbers. Sealion is still a running joke even in a scenario like this IMO). The United States has feet colder than a witch's tit when it comes to Europe, but it still clings to Pacific possessions like Hawaii, Alaska, the Philippines, etc.

Let's assume that, for some bizarre reason, Hitler scarcely reacts at all to the attack on Pearl Harbor and decides to not declare war on the United States. Let's assume that he understands German military capabilities and knows that the Wehrmacht isn't the second coming of Jesus Christ, and decides to just focus on raping Europe. No Lend/Lease? No problem!

Yes, this is assuming Hitler has a sound and capable mind. Humor me.

Now the United States would have little cause to enter the war in Europe. Without Lend/Lease, ALL American military weight is aimed squarely at Japan. Would we see the war over with by the end of 1943, assuming OTL for everything in the PTO?

 

[TheYoungPretender]

Would the US even do lend lease to the Soviets?

They had already begun some Lend Lease to the Soviets before the war started, or at least had been laying the groundwork to do so. It's where you get the "Harry Hopkins was a Russian spy" tinfoil-hattery.

I'd always thought that one of the reasons that it was Europe first was because that had been the war the administration had been preparing for during the preceding eighteen months? Remember, the big story for the December 8, 1941 paper was supposed to be that McCormick had gotten a copy of the plans for a 100 division AEF to go to Europe. Now, this was true, and Roosevelt had been looking for a way to get involved in Europe since France had gone down. By the time it would go to press, well, no-one really cared.

Even if Hitler doesn't declare war, the UK is still a co-belligerent against Japan. Given that Roosevelt had already been attempting to get the US involved in the European Theater, I assume that extending even more Lend-Lease to the UK while convoying the ships will result in a conflict breaking out. Because FDR viewed Germany as the greater threat, this seems like a safe assumption.

 

[e of pi]

Now the United States would have little cause to enter the war in Europe. Without Lend/Lease, ALL American military weight is aimed squarely at Japan. Would we see the war over with by the end of 1943, assuming OTL for everything in the PTO?

Assuming the OTL order of battle applied on Dec 7, 1941? No. As noted, the weapons that won the war in the Pacific---twenty plus fleet carriers, the Hellcat, Helldiver, Avenger, Corsair, almost 200 submarines, a working submarine torpedo, and the fleet train to put those weapons where they needed to be--all don't exist until 1943 or so, and the resources not being sent to Europe really can't be redirected--it's the old "9 women can't have one baby in a month" problem.

Now, if the order of battle is dramatically shifted in favor of a Pacific war from the start, with heavier garrisons on Pacific islands, early production of numerous carriers and escorts, testing of submarine torpedoes, and the like, that'd change, and maybe the war ending in '43 or '44 is possible, but again that's really not a change as a result of not being involved in Europe.

 

[Look More Closely Later]

...

Fair enough.

Let's assume some other things. Mix this up a bit.

Let's assume that the United States decides to go rabidly isolationist in terms of European involvement after World War I. This policy sticks through the interwar period. Here are 53,000+ American boys coming home in coffins. All have died largely in vain with Hitler's rise to power. Europe is literally on its own. (My own personal opinion is that Britain can and will endure this, probably the Soviets too just with sheer numbers. Sealion is still a running joke even in a scenario like this IMO). The United States has feet colder than a witch's tit when it comes to Europe, but it still clings to Pacific possessions like Hawaii, Alaska, the Philippines, etc.

Let's assume that, for some bizarre reason, Hitler scarcely reacts at all to the attack on Pearl Harbor and decides to not declare war on the United States. Let's assume that he understands German military capabilities and knows that the Wehrmacht isn't the second coming of Jesus Christ, and decides to just focus on raping Europe. No Lend/Lease? No problem!

Yes, this is assuming Hitler has a sound and capable mind. Humor me.

Now the United States would have little cause to enter the war in Europe. Without Lend/Lease, ALL American military weight is aimed squarely at Japan. Would we see the war over with by the end of 1943, assuming OTL for everything in the PTO?

More isolationist than the OTL stance?
Hitler quite possibly wins.
The USA war with Japan? It doesn't happen. At least not in 1941. Maybe eventually. With the USA being isolationist and all that, if there's been no two-ocean navy act, the USA might not enjoy the end result of any eventual war with Japan, though; especially if it comes once Japan has subdued China and has extra resources (plus maybe several more years of naval building) to use elsewhere.
Germany is busy running an economy by looting other countries, and using slave labour. The UK is not. Once France goes down, with German submarines sinking merchant shipping, and no lend-lease (or for that matter, since the US is being ultra-isolationist, probably no extended 'security zone' helping take some of the burden of convoy protection in the early years), it's only a matter of time before the UK has to come to terms, or face social revolution or go bankrupt. (And either of the latter of which will likely take the UK out of the war as effectively as if they had come to terms.) At best they maybe stagger on long enough to do some serious damage to Mussolini's African empire (which once the UK is out he will presumably focus on rebuilding) before calling for a ceasefire, as important goods and materials start to run short in the UK.
The Soviets, meanwhile, are not getting any aid by convoys, or any assistance by British bombing of German industry. The Germans, with the UK out of the war, are not being blockaded, and possibly as part of any 'coming to terms' deal (if that happened) are being supplied with British equipment, in addition to the output of their own industry. At best the Soviets manage to force a very bloody peace, possibly ceding lands to get it. Hitler and his colleagues continue to dominate central and western Europe.
The USA sits in splendid isolation, untouched for now, by war. (With no lend lease the European powers with interests in Southeast Asia aren't going to care a hoot about any US embargoes on Japan, and are simply going to trade with the Japanese, supplying them whatever they want to fight in China in return for a small trickle of money with which they hope to rebuild their own economies and countries eventually. And with no effective embargo, Japan doesn't feel the need to pick a fight with the USA, because they're happy enough for now with just their nasty little business in China.)

 

[Carl Schwamberger]

Fair enough.

Let's assume some other things. Mix this up a bit.

Let's assume that the United States decides to go rabidly isolationist in terms of European involvement after World War I. This policy sticks through the interwar period. Here are 53,000+ American boys coming home in coffins. All have died largely in vain

Hard to see how much more isolationist the US could have been in the 1920s. Wilsons propsals rejected by Congress, US does not support French efforts to enforce the Versailles treaty in 1923, destructive tariff barriers to trade set up...

... with Hitler's rise to power. Europe is literally on its own.

More or less was. The politically popular Nuetrality Acts remained in force while Europe deteriorated into another war. Britain and France were cut off from US industry when they started their rearmament programs

Now the United States would have little cause to enter the war in Europe. Without Lend/Lease, ALL American military weight is aimed squarely at Japan. Would we see the war over with by the end of 1943, assuming OTL for everything in the PTO?

The US did have a large incentive to participate in a European war. Even in the depths of the Depression roughly half of US product, raw materials & finished goods were exported. The bulk of that was sold to Europe. Whatever economic recovery there was in the US in 1939 was disrupted by the start of the war, & was further disrupted as it spread. US business leaders had a powerful incentive to offset the trade disruption in the short run by selling war material to the Allies (sales to Germany were less attractive). There was also the realization that for long term growth in the US a economic system beneficial to the US would have to be establisished. Roosevelt was not the only leader who understood this. While some like Henry Ford or Irene DuPont favored Germany most business leaders saw considerable disadvantages in a German dominated statist & kleptocratic European economy.

The US has never been a economic autarky & sitting idly by while the European trade shirinks killing a quarter of the US economy is going to look like a big mistake, very quickly.

 

[jkay]

But, isolationism was OTL.

Isn't it space bat for long years of atrocity news and oldest allies and friends
falling`to have an effect?

OTL was isolationist because WW1 was tbe bellishest war and Wilson went insane in Versailles.

 

[phx1138]

Would it not be possible to win by 1944?

It's well within reach for the U.S. Sub Force to crash Japan's economy by 1944 with comparatively small changes to OTL's approach. If you can push MacArthur off a pier & get the Marines/Army amphibious forces to Saipan late in '43 or into June '44 (which is OTL, IIRC), you can bring down the Japanese government (also OTL). From there, a jump to Iwo Jima & Okinawa, without the P.I. (since Dugout Dougie is busy visiting with Al Capone's old enemies), & Japan is faced with both city-burning bomber raids & the prospect of famine (the U.S. can cut movement of rice inside Japan by blowing some dozen-odd bridges & tunnels) & freezing (movement of coal by sea is a virtual non-starter already, & cutting the tunnels & bridges makes that much worse).

VE-Day in September '44?

 

[Carl Schwamberger]

It's well within reach for the U.S. Sub Force to crash Japan's economy by 1944 with comparatively small changes to OTL's approach.

Not impossible. The USN needs to fund a useful torpedo test program in the 1930s.

If you can push MacArthur off a pier & get the Marines/Army amphibious forces to Saipan late in '43

Can only happen if the necessary massive naval construction programs start circa 1938-1939 vs 1940-19 41.

or into June '44 (which is OTL, IIRC), you can bring down the Japanese government (also OTL). From there, a jump to Iwo Jima & Okinawa, without the P.I. (since Dugout Dougie is busy visiting with Al Capone's old enemies), & Japan is faced with both city-burning bomber raids & the prospect of famine (the U.S. can cut movement of rice inside Japan by blowing some dozen-odd bridges & tunnels) & freezing (movement of coal by sea is a virtual non-starter already, & cutting the tunnels & bridges makes that much worse).

VE-Day in September '44?

Maybe, but the destruction of Japans blue water cargo fleet left a considerable number of light coaster type cargo carriers. those were as or more important for internal transport as railroads. Those had to be picked off by surface & air action.

Second, in OTL after Japans principle cities were burned to the ground, its sea transport sunk, rice harvest failed, a suprise DoW by the USSR, air defense destroyed, navy sunk, and repeated atomic attacks, the cabinet was still debating what a war winning strategy might be. I'm skeptical only sinking their navy, and a transportation attack campaign would do the trick a year early.