What if Japan declared war on the Soviet Union after Pearl Harbor?

[TenThousandToddlers]

I am going to suggest that if the Japanese vigorously prosecute a war with the USSR they are finished by late 1942 or early 1943.

That's a bold take. Who exactly is going to finish them? The US could hardly stage troops and ships into Guadalcanal at that point, and the Soviets hard a lot of bloody years ahead.

Therefore, they do not have the oil necessary to maintain both the army and the fleet. Instead, they have their troops in Soviet Far East while the Royal Navy comes roaring up from Singapore and the US Fleet begins from farther eastern bases (including potentially the Philippines).

More importantly, they don't have the shipping. Navweaps has an excellent article on Japanese shipping capacity at the start of the war, and John Parshall has written on it too. They were stretching their shipping right to the limit as was. This is somewhat mitigated by the proximity of the additional conflict, but the pace of early conquests may need to slow down.

I would argue, though I'm sure the IJN would disagree, that had this all been happening the Japanese should have waited on invading the Philippines. The US couldn't supply them, and had few assets on them that could harm Japan. Letting them sit would free up shipping. (And troops, but Japan's issue is never the total number of infantry divisions; it's supplying them).

...the resounding American victory at Midway is almost ASB.

John Parshall isn't here to have an aneurism, but this thinking is pretty thoroughly savaged in Shattered Sword and follow on work. The Kido Butai was walking into an ambush, blowing it's load hitting shore installations while a strong American carrier group was positioned to clobber them. Given Hornet's disastrous day, the killing was done with only 2 American carriers and their 6(iirc) squadrons of dive bombers- There was room to spare in the win, arguably.

machine tools, etc.).

OTOH, it would also divert Japanese assets from the Pacific War. It wouldn't affect the outcomes in Malaya, the Philippines, and East Indies, but it might allow the British to hold Burma. That in turn might allow more Allied assets to go to North Africa, which could lead to better results there in early-mid 1942.

Arguably, the conquest to skip is the Philippines, initially. The DEI oil assets have to be taken and the route secured, but the Philippines don't pose much of a threat initially.

of course I have difficulty with the scenario Japan declaring war on the USSR AND the US? if they did it seems taking Sakhalin and a Pacific blockade might be about it?

To be fair, historically they declared war on the US and UK as a side adventure to their morass in China. Adding in another great power may as well happen too.

But, regarding the effect, I suspect you are right, They might try to attack down the rail lines to push deeper into Soviet territory. This isn't the Russian civil war though, and it's hard to see how they can grab anything really crazy. Mongolia is probably going to have a hard time of it though.

 

[Michel Van]

in 1938/39 Imperial Japan try to go North into USSR
The Battle of Khalkhin Gol that ended in Japanese defeat on 15 September 1939
(on 17 September happen invasion of Poland by Nazi and USSR)
After two years of negotiations on 13 April 1941, the Soviet–Japanese Neutrality Pact was sign.
(on 22 June 1941 start Unternehmen Barbarossa)
Despite Hitler demands for Japanese invasion of east USSR, the Japanese respected the Neutrality Pact
Japan focus on Europa South Asia colonies and Issue of US Pacific navy fleet
What let to attack on Pearl Harbor on 7 December 1941

the Soviet–Japanese Neutrality Pact was terminated by Stalin in 1945 follow by Soviet invasion of Manchukuo territory

 

[TDM]

Hello. I've been thinking about this for a while but couldn't find any threads on that topic. As the title says, what if the Japanese declared war on Britain and the US like they did in OTL but also attacked the USSR at the same time? Will this bennefit either Japan or Germany in any way?

Japan is already bogged down in a massive land war with a huge nation (China), no way are they going to get involved in another with an even larger more powerful nation, and even worse unlike China they can't reach anything vital in the USSR without slogging through thousands of miles of Siberia

Now if Barbarossa goes really well and western USSR collapses maybe they join in later but that's it.

 

[Band in China]

Japan is already bogged down in a massive land war with a huge nation (China), no way are they going to get involved in another with an even larger more powerful nation,

Isn't that just history? They can declare war, they just can't win.

 

[TDM]

Isn't that just history?

Sorry not sure what you mean here, yes that was the situation at some point in the past ?

They can declare war, they just can't win.

Right but they won't because of the situation they were in at that time

 

[Band in China]

Sorry not sure what you mean here, yes that was the situation at some point in the past ?

They attacked The British Empire and America to solve their quagmire in China.

 

[Carl Schwamberger]

in 1938/39 Imperial Japan try to go North into USSR
The Battle of Khalkhin Gol that ended in Japanese defeat on 15 September 1939
(on 17 September happen invasion of Poland by Nazi and USSR)
After two years of negotiations on 13 April 1941, the Soviet–Japanese Neutrality Pact was sign.

This is shortly before the US begins publicly threatening specific sanctions or embargo. A number of weak symbolic sanctions had been enacted by the US government since 1937. Now that it was clear the Japanese were acting to take full control of French Into China the US diplomats had began unofficially warning of specific and economically crippling sanctions.

(on 22 June 1941 start Unternehmen Barbarossa)
Despite Hitler demands for Japanese invasion of east USSR, the Japanese respected the Neutrality Pact
Japan focus on Europa South Asia colonies and Issue of US Pacific navy fleet

When the US and Britain began the embargo in the summer of 1941 the Japanese cabinet began discussing options should negotiations fail. While the securing of the Southern Resource Area was the option under serious discussion the details were not imeadiatly settled. The question of securing Maylasia was not settled until the true attitude of the British was determined. There was also a question of if a military campaign would be necessary in the Dutch East Indies. There was a early hope the Dutch would reach a accommodation as the French had. Many of these questions were not settled until the war started. ie: Active operations against the Dutch were not imeadiatly started in December 1941 as the Philippines had to be secured and it was hoped defeat of the Brits and USN would cause the Dutch to see reason.

The decision for war by Tojos Cabinet & the emperor came in October pending collapse of negotiations. Technically they still could have called off the war preparation after that, but it was clear through November the negotiations were dead unless the US gave up radically on its position.

What let to attack on Pearl Harbor on 7 December 1941

the Soviet–Japanese Neutrality Pact was terminated by Stalin in 1945 follow by Soviet invasion of Manchukuo territory

 

[TDM]

They attacked The British Empire and America to solve their quagmire in China.

Ah Ok yes I see what you mean

Ok the points is the two different plans (south and north) are very different things

Going south involved

1). attacking a bunch o European colonies who's colonial master where either just been defeated by Germany or rather distracted by not being defeated by Germany. Either whet colonial possessions thousands of miles away were not no1 priority for them. Plus Japan know they're weren't going to be facing europes best there anyway.

2). attacking teh US, now we know this goes badly but we also know the Japanese knew they couldn't defeat the US militarily but as I said the plan was to take enough initiative and territory to make the US just say 'Ok fuck it you can have it' (a plan based on erroneous assumptions about American lethargy and decadence)

This was also done with relatively small numbers of IJA troops than compared China, Korea, Manchukuo Taiwan etc, (the IJN was going to be the key shielding force for all this) for example the invasion of the Philippines was 150k troops, Singapore 36k, Burma was about 300k, Indochina 140k, Dutch East indies 107k (some of these troop pulling double duty)


Going North will involved invading the USSR from the wrong direction, they be stuck on the wrong end of thousands of miles of Siberia before they reach anything vital to the Soviets, on top of that if they go for it before the Germans do they're going to mess with the M/R pact.

Like I said it getting involved in another larger land war with a massive Asian country, not a very good solution to their first quagmire with large Asian country!

On top of these all these cunning plans between axis powers that involved co-ordinated efforts of entire nations that get posited in threads like these involve level of trust and joined up thinking that the Axis just didn't display OTL!


Basically plan north and plan south are not very similar, even if both were long term not good for Japan

 

[AHFan]

I would need to do more research but my thoughts are that a war with the USSR would result in no war with the US. My guess is that Japan would want coordinate more with Germany and isolate the USSR by cutting off supply lines.

 

[Ambusher11]

Japan is already bogged down in a massive land war with a huge nation (China), no way are they going to get involved in another with an even larger more powerful nation, and even worse unlike China they can't reach anything vital in the USSR without slogging through thousands of miles of Siberia

Now if Barbarossa goes really well and western USSR collapses maybe they join in later but that's it.

The Japanese in Spring 1942 after conquering the Philippines, British Malaya, and the Dutch East Indies did believe that they would eventually be ready to attack the Soviet Union... in 1944 (and I think this was premised on nothing going wrong for Japan in the meantime). So a Japanese attack on the Soviet Union during the Pacific War? Highly unlikely to occur.

 

[Carl Schwamberger]

This was also done with relatively small numbers of IJA troops than compared China, Korea, Manchukuo Taiwan etc, (the IJN was going to be the key shielding force for all this) for example the invasion of the Philippines was 150k troops, Singapore 36k, Burma was about 300k, Indochina 140k, Dutch East indies 107k (some of these troop pulling double duty)


Going North will involved invading the USSR from the wrong direction, they be stuck on the wrong end of thousands of miles of Siberia before they reach anything vital to the Soviets, on top of that if they go for it before the Germans do they're going to mess with the M/R pact.

...and it was expected the southern campaigns would be swift. From previous experience in the 1920s the Japanese anticipated that even if Valadivostock & the Maritime provinces captured, the Trans Siberian railway secured east of Lake Baikal, and the Red Army defeated in the Far Eastern Provinces, that it would require much longer to pacify the Reds or Soviet Union. Even in their weak state circa 1921-22 the Reds gave no sign of giving up and continued resisting the Japanese in the Far Eastern and Siberian regions. The Europeans and Americans would of course see reason and come to a armistice quickly. Far more economical a immediate rewards in the southern strategy.

 

[TDM]

The Japanese in Spring 1942 after conquering the Philippines, British Malaya, and the Dutch East Indies did believe that they would eventually be ready to attack the Soviet Union... in 1944 (and I think this was premised on nothing going wrong for Japan in the meantime). So a Japanese attack on the Soviet Union during the Pacific War? Highly unlikely to occur.

Right bay that's well after Barbarossa so how well the German do will very much be relevent to that.

 

[LeX]

Only way a Japanese war against the USSR might have worked is if they didn't attack the US, and instead invaded the Russian Far East in tandem with the Germans' own invasion.

 

[sarahz]

Hello. I've been thinking about this for a while but couldn't find any threads on that topic. As the title says, what if the Japanese declared war on Britain and the US like they did in OTL but also attacked the USSR at the same time? Will this bennefit either Japan or Germany in any way?

Whilst Japanese War Planning is the very definition of over optimistic i think even they would not do this unless there is something very odd in their drinking water.

 

[skarosianlifeform]

On the other hand, this slams shut the most productive Lend-Lease route into Russia - no way the Soviets can ship stuff from the US to Vladivostok now.

Because of this reason, ironically it would harm the Anglo-Americans more than help them

Main LL route being cut, plus Soviets having to fight on two fronts = Soviet Union being unable to carry the 42-44 offensives (or worse, losing) = Anglo Americans facing the full might of Germany during Alt-Overlord

It would help them against Japan, but German threat was more important for the Anglos

From the PoV of Anglos, Soviets had one job : tying down and battering Germans. Anything that would harm this objective (even if it helped elsewhere) was undesirable

 

[lionhead]

I'd like to point out again that LL to Far East was not limited to Vladivostok. They unloaded a lot of the shipping on the Kamchatka peninsula before steaming on to Vladivostok(especially military equipment). They'd unload all on Kamchatka if they can't go further. The Japanese will have to reach far inland and probably threaten all the sea around Alaska to stop LL into Russia from this route. There is always the eastern Soviet arctic route they can take and the Japanese will never reach that. The Soviets will expand this route to be able to handle more shipping if the more southern routes in the far east prove to be too difficult.

and you can't tell men like Stalin or Roosevelt that it cannot be done.

 

[Ambusher11]

I'd like to point out again that LL to Far East was not limited to Vladivostok. They unloaded a lot of the shipping on the Kamchatka peninsula before steaming on to Vladivostok(especially military equipment). They'd unload all on Kamchatka if they can't go further. The Japanese will have to reach far inland and probably threaten all the sea around Alaska to stop LL into Russia from this route. There is always the eastern Soviet arctic route they can take and the Japanese will never reach that. The Soviets will expand this route to be able to handle more shipping if the more southern routes in the far east prove to be too difficult.

and you can't tell men like Stalin or Roosevelt that it cannot be done.

Indeed. One of the reasons that the Japanese invaded Attu and Kiska in June 1942 was so they would be in a better position to disrupt communications between the United States and the Soviet Union.

 

[Sekhmet_D]

Indeed. One of the reasons that the Japanese invaded Attu and Kiska in June 1942 was so they would be in a better position to disrupt communications between the United States and the Soviet Union.

As it turned out, they made absolutely zero progress in that direction after occupying Attu and Kiska. In fact I'm not even sure they made any ATTEMPTS in that direction after occupying Attu and Kiska.

 

[Brak]

According to Hoi4, (maybe not the most reliable of a geopolitical calculator) The soviets do much worse but its not enough to defeat them. Even in OTL the soviets had very large amounts of forces stay stationed in the far east for such an eventuality. The lend lease to Vladivostok will find another way in, and wasn't too essential. So I think this is pretty accurate. The most important thing and probably a very Soviet thing to do is Scorched Earth. If the Soviets blow the Trans-Siberian RR where it is needed the Japanese will never cross Lake Baikal in the worst-case scenario.

 

[Band in China]

Ah Ok yes I see what you mean

Ok the points is the two different plans (south and north) are very different things

Going south involved

1). attacking a bunch o European colonies who's colonial master where either just been defeated by Germany or rather distracted by not being defeated by Germany. Either whet colonial possessions thousands of miles away were not no1 priority for them. Plus Japan know they're weren't going to be facing europes best there anyway.

2). attacking teh US, now we know this goes badly but we also know the Japanese knew they couldn't defeat the US militarily but as I said the plan was to take enough initiative and territory to make the US just say 'Ok fuck it you can have it' (a plan based on erroneous assumptions about American lethargy and decadence)

This was also done with relatively small numbers of IJA troops than compared China, Korea, Manchukuo Taiwan etc, (the IJN was going to be the key shielding force for all this) for example the invasion of the Philippines was 150k troops, Singapore 36k, Burma was about 300k, Indochina 140k, Dutch East indies 107k (some of these troop pulling double duty)


Going North will involved invading the USSR from the wrong direction, they be stuck on the wrong end of thousands of miles of Siberia before they reach anything vital to the Soviets, on top of that if they go for it before the Germans do they're going to mess with the M/R pact.

Like I said it getting involved in another larger land war with a massive Asian country, not a very good solution to their first quagmire with large Asian country!

On top of these all these cunning plans between axis powers that involved co-ordinated efforts of entire nations that get posited in threads like these involve level of trust and joined up thinking that the Axis just didn't display OTL!


Basically plan north and plan south are not very similar, even if both were long term not good for Japan

I agree with all of that, but it's not past the point of delusion for them to think "here comes Tsar Stalin ready to give in". There was perhaps 30-40 or so people who made decisions in imperial Japan, I even mentioned before that all the go north faction was purged in the 30s but let's indulge the OP.

The more power is concentrated, the more likely dumb shit happens.

Right bay that's well after Barbarossa so how well the German do will very much be relevent to that.

That's just the thing, the Japanese observers noted the similarities with their quagmire in China and rightly concluded that the Germans were embellishing their success.