If the US finds itself at war with Germany from April 15, 1941, Japan's agenda & the US agenda

If the US finds itself at war with Germany from April 15, 1941, Japan's agenda & the US agenda

  • a) will inevitably lead to US-Japanese war

    Votes: 19 54.3%
  • b) is unlikely to lead to US-Japanese war

    Votes: 1 2.9%
  • c) makes US-Japan war more likely than peace, but US-Japan war could still be plausibly avoided

    Votes: 15 42.9%

  • Total voters
    35

raharris1973

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a) will inevitably lead to US-Japanese war
b) is unlikely to lead to US-Japanese war
c) is more likely than not to lead to US-Japanese war, but US-Japanese war could still be plausibly avoided

Here is the set-up- The Germans decide to launch unrestricted U-Boat warfare across the Atlantic into the waters of the western hemisphere in March 1941 shortly after the passage on the Lend-Lease Act on March 11. Hitler decides that with the US openly serving as quartermaster for the British, there is nothing for him to lose by launching a borderless U-Boat offensive against all US and Allied hulls, with no "off-limits" sanctuaries.

The offensive begins in April 15, 1941. The US recognizes the clearly changed pattern in the German rules of engagement and declares war on Germany by May 15, 1941.


Assume Hitler still launches Barbarossa on time (he is working off the assumption that the US cannot do much until 1942, and that he'll definitely beat the USSR before 1941 is out, and he has a hunch that Japan will enter the war at some point in 1941 to distract already limited US forces).

In this situation, what is the likelihood of Japan joining in an attack on the western allies?

Reasons why it might be inevitable:
1. Whether the WAllies want to formally embargo Japan, or not, as a form of political protest, they will conserve their oil production for their own war effort against Germany, which means a de facto oil embargo in the near future.
2. Japan knows it will eventually, sooner or later, run out of liquid funds to purchase such oil as may remain on the global market.
3. The U.S. had already demonstrated partial hostility to Japan by embargoing scrap and high-octane fuel in 1940 and making loans to China and re-basing the Pacific Fleet in Pearl Harbor instead of San Diego.
4. With the Germans fulling engaging the Americans and British in the Atlantic and in control of Europe, and a freshly signed Japanese neutrality pact with the USSR, the geopolitics of striking to secure an East Asian resource zone will never get better.

Reasons why it might be unlikely:
1. The United States has not embargoed all fuel or frozen Japanese financial assets by May 1941.
2. Japan has only occupied northern Indochina, not central and southern Indochina
3. The U.S. has not yet set up USAFFE under MacArthur in the PI yet, nor sent B-17s, nor the Flying Tiger volunteers to China under Chennault.
4. The U.S. might be perceived as waging war against Germany with a determination that undermines any Japanese assumption that America would be inclined to cut its losses and peace out.
5. The U.S. may be harder to surprise strategically and tactically.

Small variables - Lend-Lease was formally extended to China at some point in April 1941. Maybe this happens as scheduled in OTL. Or maybe it does not, because the US is too preoccupied with the Atlantic situation for the moment.

Your thoughts?
 
Although it is possible that Japan might join the war at some point, I find it unlikely that it would do so at this particular moment. It should be noted that at this point a war against the US was not seen preferable option among Japanese leaders or even likely. Japan's alliance with Germany and Italy was seen more as a strengthening its diplomatic position than actually forming a unified block. For me it seems that Japanese did not fully grasp how this alliance was actually seen in the US, as it became one of the main issues during US-Japanese negotiation during 1941. Japan not joining Germany's war against the US, just after it hadn't done so with Barbarossa, would certainly affect American perception of Japan's aims. Also, although the military would have probably some sort of plans prepared, it would be very unprepared to act so suddenly. For example, the operation at Pearl Harbor, which was seen very crucial for Japanese success, would not be feasible, as torpedoes designed for shallow waters in the base would not be ready, and same goes for pilot training, which hadn't even begun yet.
 

raharris1973

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Although it is possible that Japan might join the war at some point, I find it unlikely that it would do so at this particular moment. It should be noted that at this point a war against the US was not seen preferable option among Japanese leaders or even likely. Japan's alliance with Germany and Italy was seen more as a strengthening its diplomatic position than actually forming a unified block. For me it seems that Japanese did not fully grasp how this alliance was actually seen in the US, as it became one of the main issues during US-Japanese negotiation during 1941. Japan not joining Germany's war against the US, just after it hadn't done so with Barbarossa, would certainly affect American perception of Japan's aims. Also, although the military would have probably some sort of plans prepared, it would be very unprepared to act so suddenly. For example, the operation at Pearl Harbor, which was seen very crucial for Japanese success, would not be feasible, as torpedoes designed for shallow waters in the base would not be ready, and same goes for pilot training, which hadn't even begun yet.

Is this a fair summary of what you are saying:

Japan would not join the war in the couple months after the outbreak of German-American war. But it is likely to at some point. Which means within a year or two?

If so would this tend to increase the Europe First tilt of US strategy more, as forces and operational plans would have been set in motion more focused on Germany? The Japanese are seen as backstabbers but still as even more the Germans’ annoying junior sidekick?
 
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In this situation, what is the likelihood of Japan joining in an attack on the western allies?

Reasons why it might be inevitable:
1. Whether the WAllies want to formally embargo Japan, or not, as a form of political protest, they will conserve their oil production for their own war effort against Germany, which means a de facto oil embargo in the near future.
2. Japan knows it will eventually, sooner or later, run out of liquid funds to purchase such oil as may remain on the global market.
3. The U.S. had already demonstrated partial hostility to Japan by embargoing scrap and high-octane fuel in 1940 and making loans to China and re-basing the Pacific Fleet in Pearl Harbor instead of San Diego.
4. With the Germans fulling engaging the Americans and British in the Atlantic and in control of Europe, and a freshly signed Japanese neutrality pact with the USSR, the geopolitics of striking to secure an East Asian resource zone will never get better.

Reasons why it might be unlikely:
1. The United States has not embargoed all fuel or frozen Japanese financial assets by May 1941.
2. Japan has only occupied northern Indochina, not central and southern Indochina
3. The U.S. has not yet set up USAFFE under MacArthur in the PI yet, nor sent B-17s, nor the Flying Tiger volunteers to China under Chennault.
4. The U.S. might be perceived as waging war against Germany with a determination that undermines any Japanese assumption that America would be inclined to cut its losses and peace out.
5. The U.S. may be harder to surprise strategically and tactically.

Small variables - Lend-Lease was formally extended to China at some point in April 1941. Maybe this happens as scheduled in OTL. Or maybe it does not, because the US is too preoccupied with the Atlantic situation for the moment.

Your thoughts?

So many of the actions against Japan were not yet executed in April, but were planned and preparation in motion. As far as US war prep and mobilization went Its not going to be trivial to reverse course on a number of these items. I expect what matters is if Japan negotiates its way to something acceptable to the US. If the negotiations are as successful as OTL then approximately the same weight in resources will go to the PTO as OTL. The expectation or hope was these reinforcements & related actions in the Pacific would show Japan that the US was serious and persuade them to negotiate a sincere settlement, at least for the near future. The instinct was to double down when diplomacy failed to show progress. With a war in the west it would make sense to continue reinforcing the Pacific to intimidate Japan and thus avoid war there.

Note that some forces were transferred from the PTO to the Atlantic in 1941. The Marine Brigade that occupied Iceland in the summer of 41 had been withdrawn from the west coast that spring for specifically this purpose. The Joint Chiefs were reluctant to draw from the recently formed Amphibious Forces Atlantic Fleet for this task. The Pacific fleet had a lower ratio of destroyers to capitol ships due to the desire for ASW assets in the Atlantic.
 
Is this a fair summary of what you are saying:

Japan would not join the war in the couple months after the outbreak of German-American war. But it is likely to at some point. Which means within a year or two?

Possibly but not necessarily. Japan's actions would depend mostly on two variables, diplomatic negotiations with the US and the war in Europe. (And these two factors obviously also influence each other.) If Germany's war seems to be going badly or negotiations with the US go well, or at least that the Japanese perceive that a diplomatic breakthrough is possible, the the war becomes more unlikely. Personally I believe that the war is less likely in this scenario compared to OTL.

It should be noted also that the US did not want a war with Japan, even though you hear claims like that from time to time from some people. The US was mostly worried about the situation in Europe and wanted to keep the situation in the Pacific peaceful. There being a war in Europe would influence American strategy in their negotiations with the Japanese, as they would want even less distractions in the region than IOTL.
 
Thinking this over, it is likely to screw Japan worse. The reasons connect to US mobilization. The initial mobilization after the French collapse in 1940 was limited by peace time law, and isolationist & America First lobbyists. The DoWs OTL were accompanied by legislation that opened the way to full mobilization.

The longer things drag out between Japan & the US, after a DoW with Germany. The farther preparations accelerate beyond those of OTL. So A attack on PI or Oahu in December may run up again more complete preparations than OTL
 
Attacking Pearl Harbor is probably a nonstarter if the US declares war on Germany since the opportunity to achieve surprise is diminished with mobilization and the operation becomes much riskier for the Japanese.

A fringe benefit is American anger remains focused entirely on Germany for being the proximate cause of the war and Japan becomes an afterthought to most Americans. The smart play is to wind down the war in China and wait out the war in Europe but that's probably unacceptable given the Japanese mentality at the time and the tempting vulnerability of European colonial possessions in SE Asia.
 
Japan's quite doomed due to this war, because now the USN has a reason to downsize the amount of CV's built*, and get more experience in using radar fire control in naval gunnery and deficiencies in submarine torpedoes depending on if the USN deploys subs in a meaningful way to interdict German/Italian Troop Ships or other cargo.

If Japan does join the war, they will start at even more of an disadvantage because not only will the US/UK be more mobilized, you would expect the Pacific to be on alert, and perhaps the Pacific Fleet on maneuvers.


*the USN might not build huge amounts of the Essex design.You'll have 10 ordered, but the 14 extra that congress funded might be forgone in favor of BB's/CA's. The Midway will probably be designed (Under a different name), we won't see the Alaska as designed (or we might see the Montana's) but battleships and more Atlantic designed CV's might be desired.
 
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The USA now gets an eight month jump on mobilization. While there is no war in the Pacific per se, now all US installations go on a wartime basis. While there may not be a full embargo on Japan, by April, 1941 there had been a large number of economic actions cutting Japan off from the dollar zone and so forth. The USA is now going to be very tight on exactly the materials the Japanese want; oil & refined products like aviation gasoline, scrap iron, other minerals, and so forth. Britain and the Netherlands may still sell some stuff to Japan, however given their financial situations neither will be selling on credit. Simply by the Allies needing the sort of raw materials the Japanese need, combined with the limited hard currency the Japanese have to buy what is offered for cash, the Japanese will still be in the sort of bind they were in OTL. China is a huge tar baby, and it is consuming resources they don't have.

OTL Japan had the choice of ending the war in China or attacking the USA/UK/etc to get the resources to continue the war. While their situation may not get as desperate as soon, sooner rather than later they need to make a choice. With the USA starting mobilization 8 months sooner, with all US bases being on heightened alert due to be at war, things are already going to be harder for them - the delay in attacking PH was as much due to the need for them to get the Kido Butai worked up with new ships/aircerew, so they really can't attack in spring/summer 1941.
 

raharris1973

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the delay in attacking PH was as much due to the need for them to get the Kido Butai worked up with new ships/aircerew, so they really can't attack in spring/summer 1941.

But a showstopper for the Pearl Harbor operation =/= a showstopper for a Japanese offensive in the western Pacific and Southeast Asia.

Western Pacific, including U.S. possessions like Guam and PI can still be attacked, it just force the Japanese to use their “traditional”, pre-Yamamoto anti-U.S. operational concept.
 
Sure the Japanese can take Guam, there's no way the USA can build it up enough here to be defended. Yes the Japanese can take the PI, if the USA is on even a half-assed war footing because of being at war it will make the Japanese work harder to get the PI. The problem is that absent PH the US Pacific fleet is untouched, and the US construction program (two-ocean navy) is already underway same as OTL. The whole idea of PH was to knock down the US Pacific Fleet and give the IJN a significant edge for long enough to establish a defensive perimeter the US will be too timid to try and pierce. If the US Pacific Fleet is intact, the IJN cannot devote the sort of effort it did OTL to support the seizure of the southern resource area (which is the real prize) because being too heavily committed there allows the US to bugger them from the east.

While be at war with Germany will shift some of the pacific forces to the Atlantic, the reality is the battle line and the big carriers don't have a purpose in the Atlantic early on. Some aid to the RN in the Med with larger ships, maybe a battleship or two to keep an eye on the twins, but basically most of the Pacific Fleet stays put.
 
There might not be an embargo against Japan for resources, but if the USA goes to war against Germany, some of the resources Japan wants are now going to be used for the American war machine and for allies against Germany. What is left for Japan?

If the USA pours everything against Germany and the Atlantic then Africa, then Europe, Pacific might receive sparse supplies.

So Japan may come to the same conclusion that the DEI and Borneo (the resource centers) are very vulnerable for the resources they need and all that stands in their way is the US Pac fleet. For this, there is no negotiations with the USA as the Americans are not embargo against Japan, there is just not that much to go around. So Pearl is a sneak attack same results. American Pac fleet is attacked on Sunday, still think sabotage of USAAF planes is main threat … Pearl and Philippines go down the same. USA industrial base is ramped up eight months earlier ……. WWII ends up in 1944
 
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