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

[EasternRomanEmpire]

I don't think the extra front would change something to the Soviets as Vladivostok isn't very important for Stalin. As the Japanese land army wasn't very motorized I think their offensive would fail as they would have way too many fronts to care about and the Soviets are much better equipped & are defending which is easier than attacking.
Even if the Japanese offensive was successful the Soviets could just defend the Trans-Siberian railway as Sakhalin and Outer Manchuria aren't important to the Soviets.
Some said that this would change something because supplies can't be sent to the Soviets but in reality most of the supplies passed trough Iran so it doesn't change much.
I think the main difference would be that after the war the Soviets would receive more land in Asia as they have been fighting Japan for much longer so maybe Japan is divided into occupation zones.

 

[nbcman]

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?

I recommend that you search for Kantokuen which were IJ's plans for the invasion of the USSR during 1941/1942:

Kantokuen - Wikipedia

en.wikipedia.org

As noted in the linked wiki article, the Japanese did not envision any offensive action against the Soviets after mid-October. A December invasion into Siberia was unthinkable.

 

[Nell_Lucifer]

There was for decades a lack of accurate information on what the Soviet Union had in Soberia, in the Far East, and the Eastern maritime provinces in military power, This has grown into a persistent myth the Far East was stripped of armies to save Moscow or the western USSR


From the 1970s and more particularly post 1990 research has show the Soviet Far Eastern Armies and Maritimes forces were stronger than supposed. and the fresh forces that 'saved Moscow' were largely from populated regions of Siberian much further west, nearer the Urals and the trans Ural regions. This web site has a daily clear summary of what the Red Army strength was in the Far East, what the trained reserves were, and what of the mobilized forces was actually sen west.

The ‘Siberian’ Divisions and the Battle for Moscow in 1941-42 | Operation Barbarrosa

While their numbers did not really decrease, their combat performance did. The soldiers with combat experience were replaced by recruits, after being recalled to Europe to fight against the Germans, while their combat vehicle and planes suffered a similar situation as with their equivalents in Europe. (Half of them not working or being in such a degraded state they would rather scrap them)

I'm going to disagree, in part. Kalkin Gol/Nomohan saw the IJ troops do OK in the field, generally inflicting more losses, for instance, but the Soviets were able and willing to ship so much more force to the area that even had the Japanese had successes, they'd have been defeated in the "2nd" Nomohan. This troop moving ability was central to Soviet strategy and planning, and central to all their successes. Look at Bagration. Bret Deveraux calls that the "operational" level of warfare, and it was the one piece the Soviets excelled at.

The Japanese were fighting with their arms tied behind their back while the Soviets were given the green card to do as they saw fit, as the Japanese high command did not want the border conflict to escalate to war. Even when the Japanese were handicapped they still inflicted on average twice their loses on the Soviets.

 

[Carl Schwamberger]

While their numbers did not really decrease, their combat performance did. The soldiers with combat experience were replaced by recruits, after being recalled to Europe to fight against the Germans, while their combat vehicle and planes suffered a similar situation as with their equivalents in Europe. (Half of them not working or being in such a degraded state they would rather scrap them)

The Japanese were fighting with their arms tied behind their back while the Soviets were given the green card to do as they saw fit, as the Japanese high command did not want the border conflict to escalate to war. Even when the Japanese were handicapped they still inflicted on average twice their loses on the Soviets.

Im not seeing that in the web site I linked, or other sources. One point of confusion among other people is not understanding how the Red Armies military districts were named. In what most Americans call "Siberia" there were from west to east: Urals Military District, Siberialn MD, Trans Baikal MD, and Far Eastern MD. Of these the Far Eastern District faced the Japanese Army on the Manchurian borders. This district contained the formations that fought the Japanese in earlier years.

Of the formations sent west:

11 divisions transferred in June-July. Nine were rifle divisions assigned to the Reserves of the STAVKA GK. These were the 153rd, 174th and 186th Rifle Divisions attached to the 22nd Army (moving from the Urals Military District), and the 91st, 119th, 166th, 107th, 133rd and 178th Rifle Divisions attached to the 24th Army (moving from the Siberian Military District). Both these armies were in transit or under orders to move on 22nd June 1941. The decision to move the 24th Army from Siberia had been made before 22 June when the 24th Army was already in Stavka reserve.


Of the 14 divisions transferred August-December five were from the Far Eastern District. The other nine were from the TransBaikail, Siberian, or Urals districts, far from the Far Eastern districts where the earlier combat vs the Japanese had been fought.

Six other infantry divisions, the 366th, 374th, 382nd, 372nd, 376th and 378th Rifle Divisions were formed/mobilized after June 22 1941. These were sent west after 90-120 days to the 59th Army in Volkhov Front defending south of Leningrad in November 1941. These were also formed in the Urals & Siberian military districts, the conscripts and cadre having little to do with the previous years combat in the Far Eastern Military District.

So, of the 31 divisions sent west five or 16%. were from the District or armies that had been in the same region the fighting with the Japanese occurred in. We can look up if any of those divisions were veterans of the previous years battle with the Japanese, but I suspect the answer is two.

During these years: 1940-1941, the Red Army more than doubled its number of total first echelon and second, third, fourth... reserve formations. This involved transferring a cadre from previously trained formations to the newly authorized. The German and US Army had the same practice, and as with them this redistributed any veterans among new formations. In the case of the Red Army the 'veterans' of Hakalin Gol had been trickling off to other formations, or to advanced schools & then often to new formations.

Note that the information Richard Sorge sent conceding the Japanese intent not to declare war became known to the Politburo & STAVKA in late October. After the bulk of the transfers were ordered.

 

[Band in China]

So.... Where are the Japanese getting the extra divisions and ships? IOTL the Centrifugal offensive took up 80% of Japan's merchant marine which was already insufficient for peacetime use, the homeland was forced to work off of stockpiles while operations in China were curtailed. Are the Japanese using the 2nd and 3rd rate units left in China with minimal logistical nor aerial assistance or are they forgoing the "Southern Resource Area" which begs the question of why attack the USA in 1941?

Historically the "Hokushin-ron" Northern Road faction favouring war with the USSR, but it was purged after the failed Feb 26 coup in 1936 and fell out of favour due to the war in China. Sadao Arak was the only person of significance who favoured Hokushin-ron and he resigned as war minister due to ill health in 1934. There simply wasn't anyone left advocating for a war with the USSR in the circles of power, that's why even upstart officers couldn't start a war. It's not their first rodeo either, the Japanese empire had occupied vast swaths of the Far East to little effect during the Russian Civil War and they know of the difficulty of occupying and extracting anything of value from the region.

The Japanese were fighting with their arms tied behind their back while the Soviets were given the green card to do as they saw fit, as the Japanese high command did not want the border conflict to escalate to war. Even when the Japanese were handicapped they still inflicted on average twice their loses on the Soviets.

I mean yeah, they were handicapped by the war in China they started but could not finish-that fact won't change and will actively get worse once arms start flowing to China via Burma and Qinghai. The Japanese will be hard pressed to take Burma as IOTL with the added strain of fighting a USSR that's doesn't have any political issues supply China.

 

[Nell_Lucifer]

Snip

I am not talking about the movement of divisions, but of individual soldiers. Like in all armies, some divisions are strengthened, dissolved or restructured. The same Soviet divisions that remained on the Manchurian border were restructured in some part, they were not moved. From what I've seen, the overall quality of the troops decreased from 1941 to 1942 while the overall strength remained relatively the same.

So.... Where are the Japanese getting the extra divisions and ships? IOTL the Centrifugal offensive took up 80% of Japan's merchant marine which was already insufficient for peacetime use, the homeland was forced to work off of stockpiles while operations in China were curtailed. Are the Japanese using the 2nd and 3rd rate units left in China with minimal logistical nor aerial assistance or are they forgoing the "Southern Resource Area" which begs the question of why attack the USA in 1941?

Historically the "Hokushin-ron" Northern Road faction favouring war with the USSR, but it was purged after the failed Feb 26 coup in 1936 and fell out of favour due to the war in China. Sadao Arak was the only person of significance who favoured Hokushin-ron and he resigned as war minister due to ill health in 1934. There simply wasn't anyone left advocating for a war with the USSR in the circles of power, that's why even upstart officers couldn't start a war. It's not their first rodeo either, the Japanese empire had occupied vast swaths of the Far East to little effect during the Russian Civil War and they know of the difficulty of occupying and extracting anything of value from the region.

I assume they use their original 24 or so divisions stationed on the Manchurian border in 1942. That's around 1 million manpower. In theory it should not affect the southern operations as the Manchurian and Korean infrastructure would supply the troops for the Soviet invasion.

I mean yeah, they were handicapped by the war in China they started but could not finish-that fact won't change and will actively get worse once arms start flowing to China via Burma and Qinghai. The Japanese will be hard pressed to take Burma as IOTL with the added strain of fighting a USSR that's doesn't have any political issues supply China.

No, I mean they were not given reinforcements that were available, be it reserve units or air support. Most of the fighting was at the regimental level, with no coordination from up-high. The Japanese did not want to escalate to a war with the Soviet Union, so as to not provoke them further, they kept the intensity and supply at the level of a border skirmish, while the Soviets did not care and well full 100% at it.

 

[Nivek]

If Japan goes north,them pearl harbor doesn't happen

 

[sdgottsch]

The Japanese were fighting with their arms tied behind their back while the Soviets were given the green card to do as they saw fit, as the Japanese high command did not want the border conflict to escalate to war. Even when the Japanese were handicapped they still inflicted on average twice their loses on the Soviets.

From Wikipedia: On 27 June the Japanese Army Air Force's 2nd Air Brigade struck the Soviet airbase at Tamsak-Bulak in Mongolia. The Japanese won this engagement, but the strike had been ordered by the Kwantung Army without obtaining permission from Imperial Japanese Army (IJA) headquarters in Tokyo. Tokyo promptly ordered the JAAF not to conduct any more air-strikes against Soviet airbases.

If Tokyo had not stopped the JAAF from strikes against the Soviet airbases (which they were very successful from 22-27 June) then my opinion is the Soviets wouldn't have had localized air superiority to bomb the Kwantung Army in mid-to late July and therefore it would have been a ground style battle.

 

[Alex1guy]

A more interesting scenario would be if Japan did not go to war with anyone but China and the USSR. If they had limited themselves to these and declared their fight one of anti-communism there's a good chance, they would have secured Manchuria and the Russian east.

They can't not go south. They needed oil to keep assualting China after America cut them off for invading French Indo China. They needed to invade Indochina to stop supplies getting to China from the West.Indonesia had oil, the Soviets did not (at least not yet). Pearl Harbour wasn't some crusade against democracy or imperialism, it was a (poorly) calculated risk to keep the war effort in China going. All japanese actions were predicated on subduing China. The western democracies were seen as weak, not without some precedent mind you as France had fallen and the UK appeared on the ropes. The US was viewed as not having the stomach for a protracted war so Japan went south, literally and eventually metaphorically.

 

[CaptainCalvert]

In 1940, the Japanese estimated that the Soviet forces stationed from Vladivostok to Mongolia consisted of thirty rifle divisions, two cavalry divisions, nine tank brigades and one mechanised brigade.

Their estimate was somewhat off, especially where it came to the extent of mechanisation - the Red Army in Asia actually boasted nineteen rifle divisions, six tank divisions, four mechanised divisions, two motorized rifle divisions, one cavalry division, and ten rifle brigades.

A proportion of these forces were hurriedly moved westward when Barbarossa hit (these were the reinforcements that surprised the Germans with their appearance as you say); the best chance the Japanese would have in a 'strike north' move would therefore be to coordinate the timing of their offensive with that of the Germans.

I agree their best chance would be a coordinated strike, but if German intel was either so bad they thought the ussr would quickly collapse (and that all the armies had been destroyed - yet again) or their commanders wilfully disregarded the intel in favour of their imaginations, then any coordination beyond: "Attack USSR on or shortly after 22nd June" is effectively impossible.

An interesting twist is that if a Japanese attack is to be tied in with Barbarossa, won't Sorge pass on the warning of an attack on the USSR to be coordinated with a German attack? Stalin then has a warning about Barbarossa from a trusted source that can't be dismissed as capitalist scheming.

Barbarossa will still be destructive, but a bit less so and is likely to be a bit slower and more costly probably with fewer or smaller mass captures.
Meanwhile, the Japanese run into a strong, mobile and armoured force in the east and get mired.

 

[dfl_90]

On the less military focused side of things, this could possibly lead to Japan exiting the war sooner. I'm not certain exactly when the line of thinking developed among Japan's leadership, but by late 1944 they were looking at the Soviet Union as a potential neutral party to open peace negotiations with the US. That desperate and ultimately incorrect belief that the Soviets would break with their capitalist allies and support a conditional surrender contributed in some part to Japan hanging on for the final few months of the war. In addition to whatever military pressure they feel from the Soviets in the proposed scenario, they are now absent a major neutral power to pin their hopes on. That might make an unconditional surrender seem more inevitable as the noose tighten.

 

[TenThousandToddlers]

The Japanese were fighting with their arms tied behind their back while the Soviets were given the green card to do as they saw fit, as the Japanese high command did not want the border conflict to escalate to war. Even when the Japanese were handicapped they still inflicted on average twice their loses on the Soviets.

I'm not disagreeing with you. The Japanese seemed to generally outperform their counterparts man to man. The Soviets, however, had amassed such a pile of men and armor, and in a fairly short time, that the short and medium term fighting was essentially hopeless for Japan. They could of course shift more forces to the area, but a longer term, full born war with the USSR -and their 300 some standing divisions- was a losing proposition. The Japanese tactical performance, though laudable in some ways* didn't stack up to the terrible operational and strategic situation.

The Soviet attack, utilizing their rail and road assets, came as a complete shock. The Japanese didn't really view it as possible for the Soviets to build up so fast and so quietly. The Japanese were unable to match the build up speed, meaning that the massive force and firepower ratios in favor of the Soviets would continue barring the war moving onto Japanese territory. If the war did that, the Japanese were losing anyway.

*sorta... The 23rd division performed well when shooting at the enemy. However, they failed to communicate that they were under attack from 3 sides by a conglomeration that might be termed a combined arms army. They failed to attempt withdrawal until far too late. They failed to attempt any sort of breakout, at least regarding most of the sub units. To their credit, though, they stopped the Soviet cold in the frontal and Northern attacks. Some of this is probably due to the Soviets been somewhat inept, particularly in the Northern attack (If I remember correctly; it's been a while since I really dug into it, but I did have a class that focused on it rather heavily as a case in point for supply/operational warfare), but a lot of it has to be credited to the Japanese. They would go on to show similarly tough characteristics, also to little avail, in the Pacific war.

-------- (General thread reply, not specific to you, Mr. Lucifer)

Of course, that doesn't apply as much in the OP's situation. A 1941 attack would see the Soviets be unable to match the total force from Japan, particularly as Japan shuffled in more forces and the Soviets took losses. The IJN's complete naval domination of the area would grant some degree of mobility advantage to the Japanese for any coastal operations, though inland the Soviets still probably move around better.

The bigger issue there seems to be that it doesn't offer a fix for Japans current issues. Not oil, not steel, not good relations with the Americans, not reduced aid to Chinese opponents. What it does do is open up a massive meatgrinder that will pull in men and material faster then the fighting in China. All for what? Vladivostok? Occupying the rest of Sakhalin, a bunch of mostly useless islands, maybe grabbing bits of Kamchatka?

Worse, Japan is still going to war with the UK, US, French holdings, the Dutch and Australia. Suddenly there's a humongous shipping crisis, as all those beans and shells and boys going to Siberia need ships to get them to there from Japan.

Maybe, to play devils advocate, they could force a negotiated peace with Stalin in Asia. Hell, maybe even it shocks Ioseph so badly that his government fails or something.

I don't know if the success would actually help Japan, as they'd still need to keep the Kwantung army supplied and large. Meanwhile, their doom approaches from the Pacific.

 

[CaptainCalvert]

I'm not disagreeing with you. The Japanese seemed to generally outperform their counterparts man to man. The Soviets, however, had amassed such a pile of men and armor, and in a fairly short time, that the short and medium term fighting was essentially hopeless for Japan. They could of course shift more forces to the area, but a longer term, full born war with the USSR -and their 300 some standing divisions- was a losing proposition. The Japanese tactical performance, though laudable in some ways* didn't stack up to the terrible operational and strategic situation.

The Soviet attack, utilizing their rail and road assets, came as a complete shock. The Japanese didn't really view it as possible for the Soviets to build up so fast and so quietly. The Japanese were unable to match the build up speed, meaning that the massive force and firepower ratios in favor of the Soviets would continue barring the war moving onto Japanese territory. If the war did that, the Japanese were losing anyway.

*sorta... The 23rd division performed well when shooting at the enemy. However, they failed to communicate that they were under attack from 3 sides by a conglomeration that might be termed a combined arms army. They failed to attempt withdrawal until far too late. They failed to attempt any sort of breakout, at least regarding most of the sub units. To their credit, though, they stopped the Soviet cold in the frontal and Northern attacks. Some of this is probably due to the Soviets been somewhat inept, particularly in the Northern attack (If I remember correctly; it's been a while since I really dug into it, but I did have a class that focused on it rather heavily as a case in point for supply/operational warfare), but a lot of it has to be credited to the Japanese. They would go on to show similarly tough characteristics, also to little avail, in the Pacific war.

-------- (General thread reply, not specific to you, Mr. Lucifer)

Of course, that doesn't apply as much in the OP's situation. A 1941 attack would see the Soviets be unable to match the total force from Japan, particularly as Japan shuffled in more forces and the Soviets took losses. The IJN's complete naval domination of the area would grant some degree of mobility advantage to the Japanese for any coastal operations, though inland the Soviets still probably move around better.

The bigger issue there seems to be that it doesn't offer a fix for Japans current issues. Not oil, not steel, not good relations with the Americans, not reduced aid to Chinese opponents. What it does do is open up a massive meatgrinder that will pull in men and material faster then the fighting in China. All for what? Vladivostok? Occupying the rest of Sakhalin, a bunch of mostly useless islands, maybe grabbing bits of Kamchatka?

Worse, Japan is still going to war with the UK, US, French holdings, the Dutch and Australia. Suddenly there's a humongous shipping crisis, as all those beans and shells and boys going to Siberia need ships to get them to there from Japan.

Maybe, to play devils advocate, they could force a negotiated peace with Stalin in Asia. Hell, maybe even it shocks Ioseph so badly that his government fails or something.

I don't know if the success would actually help Japan, as they'd still need to keep the Kwantung army supplied and large. Meanwhile, their doom approaches from the Pacific.

Interesting points.
But there was already a nonaggression pact in place, so the objective would surely have to be better than gaining a (slightly better) settlement with the USSR.
There is the possibility that defeating the soviets would aid the Germans, but why would Japan spend scarce resources to support a bunch of people on the other side of the world who doesn't share their strategic goals?

 

[Intosh]

It will throw the Russian war effort into the chaos as they can't move their troops west out of Vladivostok. Moving factories east will be more difficult if you have to worry about a Japanese invasion from that direction. The political effect of Japan invading may result in a political implosion of the Russian government. If someone kills Stalin the government may collapse extending the war by years.

If you look at a map, you will that the USSR is very very huge.

And the Japanese can only attack Vladivostok region and not the Ourals or Central Siberia that are thousands of miles in the west.

 

[mjwebb76]

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. Recall that the fundamental (albeit erroneous) premise behind Pearl Harbor was that the US would be crippled for 6 months. During that 6 months the Japanese Army could rush south and capture oil of South East Asia while the IJN would capture an impenetrable island wall such that the USA would sue for peace. IOTL it sortof/kindof worked except the US was angrier than anticipated and the fleet wasn't as crippled as intended. In this scenario, they attack Pearl Harbor and then turn to Siberia. 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).

Perhaps the OP meant that the Japanese would declare war on the USSR but not really do much, creating a sortof phony war scenario. In other words, the first six months of 1942 would play out basically as IOTL withe the Japanese Army racing south and the USSR and Japan don't really do much. I still think this ultimately puts Japan in a worse spot since there will be an incentive for the US and the USSR to collaborate more closely (e.g. permit US to use airbases in the Soviet Far East thereby having easier ability to bomb Japanese cities).

The one way a declaration of war may help the Japanese is if it butterflies away Midway. While I am normally not a big fan of disconnected events having massive butterfly effects, the resounding American victory at Midway is almost ASB. Therefore, it strikes me as plausible that small changes cause Midway to not occur as it does IOTL. In this case, the IJN may remain viable for a longer period of time.

 

[EasternRomanEmpire]

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. Recall that the fundamental (albeit erroneous) premise behind Pearl Harbor was that the US would be crippled for 6 months. During that 6 months the Japanese Army could rush south and capture oil of South East Asia while the IJN would capture an impenetrable island wall such that the USA would sue for peace. IOTL it sort of/kind of worked except the US was angrier than anticipated and the fleet wasn't as crippled as intended. In this scenario, they attack Pearl Harbor and then turn to Siberia. 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).

Perhaps the OP meant that the Japanese would declare war on the USSR but not really do much, creating a sortof phony war scenario. In other words, the first six months of 1942 would play out basically as IOTL withe the Japanese Army racing south and the USSR and Japan don't really do much. I still think this ultimately puts Japan in a worse spot since there will be an incentive for the US and the USSR to collaborate more closely (e.g. permit US to use airbases in the Soviet Far East thereby having easier ability to bomb Japanese cities).

The one way a declaration of war may help the Japanese is if it butterflies away Midway. While I am normally not a big fan of disconnected events having massive butterfly effects, the resounding American victory at Midway is almost ASB. Therefore, it strikes me as plausible that small changes cause Midway to not occur as it does IOTL. In this case, the IJN may remain viable for a longer period of time.

Stalin would NEVER allow for something from the U.S. to be on his territory, instead if Japan had declared war on the Soviets but not done anything the Soviets might attack Japan a little bit earlier OTL as Stalin still had troops in the Far East which while not as good as special troops chosen for this operation the Soviets once Germany is clearly done for might launch an offensive in Manchuria earlier who would be slightly slower than the one OTL but would manage to take most of Korea as they would have more time to make gains.

 

[Anarch King of Dipsodes]

It isn't going to happen while Colonel Tsuji is around. He was in Manchuria during Khalkin-Gol (as an observer), and he came away with that very strong belief that We Don't Want To Do This Again. When the arguably maddest dog in the whole kennel said "Don't", people listened. (And he was quite influential in the high command, despite his modest rank.)

Also, Japan was almost completely unprepared for war with the USSR at that time.

However, if Japan did stumble into war with the USSR then, it would certainly help the European Axis. It would divert Soviet assets from the European Front, of course. And it would close Vladivostok as a port for Lend-Lease deliveries. AIUI, about half of all Lend-Lease cargo went through Vladivostok. Though again AIUI, only "non-military" goods were allowed through (food, railroad equipment, trucks, metal ingots, 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.

And OYAH, it might cause the Stavka to refrain from some of the late winter 1942 counterattacks that failed badly (Izyum and Kerch).

One other point: if Japan was going to attack on the USSR, it would (IMO) be in the summer or fall of 1941, when the Germans were blitzing eastwards against apparently negligible resistance. Once the Soviets had repulsed the Germans at Moscow, that perception changed. And that happened just before Pearl Harbor.

 

[thaddeus]

Some said that this would change something because supplies can't be sent to the Soviets but in reality most of the supplies passed trough Iran so it doesn't change much.

that is true but it took a while for the route to be fully developed, the Soviets would lose the one certain route. my speculation (or attempt at a POD) was for Leningrad to fall, that would close the Arctic route at least for a time, and make it appear a Japanese blockade of the Pacific route might finish the Soviets.

Perhaps the OP meant that the Japanese would declare war on the USSR but not really do much, creating a sortof phony war scenario. In other words, the first six months of 1942 would play out basically as IOTL withe the Japanese Army racing south and the USSR and Japan don't really do much.

The one way a declaration of war may help the Japanese is if it butterflies away Midway. While I am normally not a big fan of disconnected events having massive butterfly effects, the resounding American victory at Midway is almost ASB. In this case, the IJN may remain viable for a longer period of time.

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?

 

[Alex1guy]

Its baffling in hindsight that the Japanese didnt think SU should be prioritized. Japan can never win on its own and only Germany winning offers the Japanese any prospects of success.
In such a scenario getting Spain in on the Axis side would be critical. KM and air power based their would shut the southern route and ensure Japan a free hand against the British (eg, the Germans could have offered something back). Indeed, a close Accord between the axis in 1940 is a major missed opportunity.

Japan needed oil. The USSR didn't have oil. 90 percent of its oil came from America, America had cut off the oil. Indonesia had oil. They needed to head south. Germany and Japan were more allies of opportunity with no real shared goals, just common enemies. Japan's plans were baffling because had no prospects of success, the war doomed because it had no strategic coherence or plan. They just kept doubling down and hoping for the best. Start a war in China with no plan of winning except hoping China will fall apart, they then started a war with the British and the US on the same premise. Granted an attack on the USSR would fit the pattern of decisions made with little strategic sense based on high hopes...

 

[CaptainCalvert]

Japan needed oil. The USSR didn't have oil. 90 percent of its oil came from America, America had cut off the oil. Indonesia had oil. They needed to head south. Germany and Japan were more allies of opportunity with no real shared goals, just common enemies. Japan's plans were baffling because had no prospects of success, the war doomed because it had no strategic coherence or plan. They just kept doubling down and hoping for the best. Start a war in China with no plan of winning except hoping China will fall apart, they then started a war with the British and the US on the same premise. Granted an attack on the USSR would fit the pattern of decisions made with little strategic sense based on high hopes...

Japan attacking China and Germany attacking the USSR appear to have been based on similar false premises. In that sense, they are ideal allies since Willpower, Destiny and Optimism are the top three considerations in planning for both.