What are some Scenarios where the US could Declare war on Japan First?

I was thinking about this a bit, and I am curious about the US declaring war on Japan first.

I am specifically focusing on a timeline where Japan (for whatever reason) chooses to not attack the US, but instead only attack the other WAllies. This is mainly in consideration of the US showing multiple concerns over Japan being able to threaten the UK.

Would the US declare war first if it saw a serious threat to the British empire after a Japanese invasion?

Would the US declare war first in a timeline where Japan may be on the verge of defeating China?
 
If Japan went after the Western colonial powers and left the US alone, Roosevelt would be seeking a casus belli. The "balance of power" isn't an argument he could sell to the people, so I guess he'd have to put US Navy forces "at risk" to lead to a confrontation large enough to justify a declaration of war. Lacking a Pearl Harbor, a conditional peace would be the likeliest result.
 
Its hard. If Japan ignores the Americans and strikes at Britain and the Dutch, how does Roosevelt get Congress to go along?

I'm not sure really how he can. America declares war to protect British colonies but not Britain herself? How do you make the case for war?

Its a hell of a gamble but how can things turn out worse for the Japanese? What's worse than the atomic bomb falling on your head?
 
Would the US declare war first if it saw a serious threat to the British empire after a Japanese invasion?


Its not difficult to get the US into this Japa/European War. OTL the US arranged to sell large quantities of arms to Germanys enemies & restricted sales of anything to Germany by requiring cash, imposing buercratic delays, and other obstacles. The US arraigned a Neutrality or Exclusion Zone for a extended distance from its territory. That Exclusion zone was extended & eventually was expressed in a US Naval base and Marines inside the war zone on Iceland. The US provided its military personnel as trainers where the French and British purchased its weapons. Germany not wanting to provoke the US went along, but by the spring of 1941 was starting a clandestine war between agents in Latin American, in the autumn a naval war in the Atlantic.


Previous to Japans attack in December 1941 the Dutch, US, and Britain had been systematically sharing intelligence among their service in the Pacific and Asia. They had also been consulting at the highest levels for joint war plans. So its not like the US is on the other side of some sort of wall of neutrality. There is also the matter of the War Warning sent 27 November. That specified any Japanese forces sighted were to be considered "hostile". In the military parlance I was trained in that was permission to shoot.


The first thing that occurs from the first day is the US is running its usual military patrols in the region of the Philippines, Guam, Wake, ect... Those would be stepped up imeadiatly as common prudence. The US has no worthwhile assurance it will not be attacked soon. So increased patrols, and alert of the military forces is certain. The second major action would be to establish a Exclusion or Neutrality Zone around US & Philippines territory. The obvious precedent is the previous Exclusion Zone in the Atlantic. Patroling that is certain as well. Third thing is accelerate the shipment of arms and material to both the Philippines and the Allies, the Dutch and Brits. All that makes for a volatile & tense mix. Bottom line is Congress may not be consulted by naval officers on the spot, particularly Japanese naval officers making a judgment call on attacking or not on warships or a cargo ship convoy, where there is any ambiguity.
 
Very easy, Japan declares war on Britain and the Netherlands but not the US. US extends Atlantic convoy patrols it was already doing pre Pearl Harbor OTL to the Pacific. Japan sinks some ships and BOOM, war.
 
There is also the matter of the War Warning sent 27 November. That specified any Japanese forces sighted were to be considered "hostile". In the military parlance I was trained in that was permission to shoot.
In the War Warnings of 27 November, the Navy was told to "Execute an appropriate defensive deployment" and the Army was told "the United States desires that Japan commit the first overt act" (emphasis mine). I would think that this would remain the policy even with stepped up patrols in an Philippine Exclusion Zone. That way FDR can make the claim that "we were minding our own business on routine patrol when the Japanese attacked us without provocation".

Source: https://olli.gmu.edu/docstore/700docs/0901-703-PEARL HARBOR WARNINGS.pdf

And at some point, there is just going to be SO much war material in the Philippines that the IJN just will not be able to ignore it ...
 
Any such scenario ha one huge stumbling block: if the US declares war on Japan, Japan will invade the Philippines, and the US cannot defend the Philippines. Thus by declaring war, the US dooms the Philippines to Japanese conquest, and would be responsible for the ensuing hardships for the Philippine people.

Now it is quite possible that Roosevelt would simply ignore this issue, perhaps in the delusion that the US forces there would repulse Japanese attack, or simply out of indifference to Philippine interests. However, would Philippine leaders go along with this? They would lobby furiously against such a declaration. [zzzz...]
 
Any such scenario ha one huge stumbling block: if the US declares war on Japan, Japan will invade the Philippines, and the US cannot defend the Philippines. Thus by declaring war, the US dooms the Philippines to Japanese conquest, and would be responsible for the ensuing hardships for the Philippine people.

Now it is quite possible that Roosevelt would simply ignore this issue, perhaps in the delusion that the US forces there would repulse Japanese attack, or simply out of indifference to Philippine interests. However, would Philippine leaders go along with this? They would lobby furiously against such a declaration. [zzzz...]

The idea that the Philippines were indefensible had been around for three decades. It had been accepted as policy and had been a core part of War Plan ORANGE for two decades. When the Embargo Acts were passed and the decision to move the fleet to Oahu, fortify select Pacifc islands, and build up a viable military force in PI it was all done with the understanding PI would remain indefensible for near a year, possibly more. The RAINBOW plans had the same recognition That without a extended build up it was not practical to defend the place. Roosevelt, or more accurately the Warhawks decided for the risk anyway. Gambling on pressuring Japan gambled the loss of PI.

Congress voting for a DoW is a broader dynamic. Lots or reasons among the members for a vote against. Concerns about the defensibility of PI was one among many, and not the foremost among the objections.
 
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Very easy, Japan declares war on Britain and the Netherlands but not the US. US extends Atlantic convoy patrols it was already doing pre Pearl Harbor OTL to the Pacific. Japan sinks some ships and BOOM, war.
Good points.

Of course Imperial Japan never actually declared war on the US. Just broke off negotiations and started tbe fighting. So, technically, the US did make the first DOW!

(Clearly that isn't what the OP meant though.)
😀
 
In the War Warnings of 27 November, the Navy was told to "Execute an appropriate defensive deployment" and the Army was told "the United States desires that Japan commit the first overt act" (emphasis mine). I would think that this would remain the policy even with stepped up patrols in an Philippine Exclusion Zone. That way FDR can make the claim that "we were minding our own business on routine patrol when the Japanese attacked us without provocation".

Source: https://olli.gmu.edu/docstore/700docs/0901-703-PEARL HARBOR WARNINGS.pdf

And at some point, there is just going to be SO much war material in the Philippines that the IJN just will not be able to ignore it ...

The actions I described creates a political fuel air bomb. Compared to the Japanese the Germans were a model of circumspection. Gunfights between the US patrols and Japanese are inevitable and much sooner than later. As in the Atlantic US warships operating in what the enemy considers the war zone, escorting US flagged ships through technically international waters, and the Exclusion Zone, makes the odds of gunfights rather 'high'. OTL German and Japanese mistakes and considered decisions made the US Congress irrelevant. In 1941 intentional or not the fuel was on the floor.

Very easy, Japan declares war on Britain and the Netherlands but not the US. US extends Atlantic convoy patrols it was already doing pre Pearl Harbor OTL to the Pacific. Japan sinks some ships and BOOM, war.

The US had already been organizing patrols and escorted convoys to PI before 7 December. The Pensacola Convoy had been designated before hand.
 
The actions I described creates a political fuel air bomb. Compared to the Japanese the Germans were a model of circumspection. Gunfights between the US patrols and Japanese are inevitable and much sooner than later. As in the Atlantic US warships operating in what the enemy considers the war zone, escorting US flagged ships through technically international waters, and the Exclusion Zone, makes the odds of gunfights rather 'high'. OTL German and Japanese mistakes and considered decisions made the US Congress irrelevant. In 1941 intentional or not the fuel was on the floor.



The US had already been organizing patrols and escorted convoys to PI before 7 December. The Pensacola Convoy had been designated before hand.
Sending convoys to the PI after war has broken out between Japan and the Europeans is high risk. With any convoy sent, there has to be the assumption that those ships and their cargoes may be lost. I think that would be especially a problem for troop ships. How much of an escort force might be assigned to a convoy? I can imagine the Pacific Fleet providing a powerful distant cover force to some point west of Wake.

What route would convoys take between Hawaii and the PI? Would they sail through the Japanese mandates? Related to all that, would Japan even invade the Gilbert Islands while still not at war with the USA?

Does the US reinforce Guam at some point? Aircraft are needed as much as ground forces, perhaps more so. A couple of fighter and/or dive bomber squadrons, a squadron of seaplanes, and a couple of defense battalions at a minimum.
 
Good points.

Of course Imperial Japan never actually declared war on the US. Just broke off negotiations and started tbe fighting. So, technically, the US did make the first DOW!

(Clearly that isn't what the OP meant though.)
😀
Weird thing is that Hitler did declare war, whereas for other countries he just invaded them (the UK and France declared war to Germany due to their pact with Poland). So he could have just started hostilities with Operation Drumbeat.
 
Sending convoys to the PI after war has broken out between Japan and the Europeans is high risk.


Of course its high risk. At the same level as the convoys that carried the USN base personnel & Marines to Iceland in the summer of 1941. Hitler was briefly infuriated, but was wrapped up in preparations and execution of Op Barbarosa. The general result was German & US warships were shooting at each other in the autumn. That was something the Warhawks in the US were not opposed to. The whole idea of establishing the Exclusion Zone in the Atlantic, relocating its boundary eastwards, occupying Iceland, preparing to occupy Portuguese Azores, seconding US military personnel to British combat forces as "Trainers", was to wave a red cape at Germany. The Axis could either back of from US forces trailing the cape, or fight. The same applies to the Pacific. The Japanese can either back off from US flagged ships, or stop them.

With any convoy sent, there has to be the assumption that those ships and their cargoes may be lost. I think that would be especially a problem for troop ships. How much of an escort force might be assigned to a convoy?


That was implied risk for the Pennsacola Convoy that was to proceed after the November War Warning. That it would be caught enroute was considered likely were the Japanese to attack. It was hoped the Pensacola Convoy and any subsequent would deliver well before a Japanese attack.

I can imagine the Pacific Fleet providing a powerful distant cover force to some point west of Wake.

What route would convoys take between Hawaii and the PI? Would they sail through the Japanese mandates?

Cargo ships to PI pre Dec 1941 took a circle route from the US west coast, that on a flat map looks like it loops around the northern Mandate Islands. After 7 Dec Everything to S Pac too a long extended loop south east of everyones Mandates. To best understand the trans pacific route a globe is needed. Flat Mercator projections are near useless. After 7 Dec the convoys to PI were canceled. The cargo ships were sent individually & in small packets south in the easter Pacific & then west to Australia. There they were formed into convoys for deliveries to the Dutch East Indies. There was the idea of running a convoy from Java north to PI, but that was never judged practical and a few fast blockade runners sent.

Related to all that, would Japan even invade the Gilbert Islands while still not at war with the USA?

IIRC most or all of the Gilberts were British territory.

Does the US reinforce Guam at some point? Aircraft are needed as much as ground forces, perhaps more so. A couple of fighter and/or dive bomber squadrons, a squadron of seaplanes, and a couple of defense battalions at a minimum.

There were no near term plans to defend Guam. From the PoV of late 1941 it was indefensible. Wake was a gamble the USN lost.
 
IIRC most or all of the Gilberts were British territory.
They were, but so? It is still a valid question. Would the Japanese still consider a grab for the Gilberts (and Solomons, Bismarcks, New Guinea......New Caledonia?.....Fiji?] a part of a Southeast Asian grab for resources primarily focused on the DEI, Malaya, Singapore and shutting the Burma road that is deliberately bypassing US possessions? Or would their OP plan, because of its intentional avoidance of treading on US possessions, also avoid treading on *any* foreign possessions east or southeast of the Mandates to reduce chances of provocation of or contact with Americans?
 
About all I can say is there was a group in Japan that saw the Pacifica territories as a natural extension of the Japanese empire. Seizing those territories was worked into the plans of OTL. If they don't seize them outright they may plan on demanding them as part of a peace settlement.
 
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