WI: Soviet Invasion of Honshu

[Curiousone]

Ahh wrote a long post & then accidentally shut the tab, frustration.

Don't think the Soviets would have been that interested in Honshu to b honest. Soviet aims in Japan seemed to be limited to ensuring control of the Sea of Okhotsk, hence Stalin's aim to occupy Hokkaido from Rumoi to Kushino (the northern third of the island) and his hope to have that area as a Soviet occupation zone even after Japan's surrender. That leads me to suspect that Stalin was only interested in the main islands of Japan as far as he could expect to benefit and that he wasn't as concerned about Japan as he was about Germany.

IF the Soviets sensed an opportunity to land in northern Honshu though, I suppose they might just be able to do it after taking Hokkaido, but if they land they face the possibilty of fighting on Honshu with no defined end until Japan surrenders as there are no natural barriers to prevent the Japanese from sending up forces from Kanto to attack the Soviet lodgement on Honshu.

Is it too big an assumption to have Stalin as unconcerned about casualties, having land-grabbing motives (for at least what he can bargain in concessions for it later)?

Upon further reading, Calbear's correct, by October the Tsushima strait would likely be heavily mined, a serious naval crossing is thus quite likely to fail even if the Soviets spend the winter sweeping the strait. Before the war the Soviets had the largest airborne forces in the world, and though most became Guards Divisions during the war, the 4th Airborne Corps had had active combat drop experience. Transporting them would likely require bring the Tupolev TB-3 out of retirement once again. Though the obsolete craft had been retired before Barbarossa began, the massacre of the Soviet Air Force in the first days of the German invasion led to it being rushed back into service, where it performed heroically against far superior enemy aircraft. Now by the summer of 1945 there were only ten left in active service as they had been gradually replaced by more modern bombers, but there were likely over a hundred left in flyable condition, giving the Soviets the ability to land 3-4000 paratroops on Honshu.

Now I'm about to go into a lecture so I can't do much just now, but do you have any idea of airfields in northern Honshu they might try to take?

I don't see the Soviets invading via the Tsushima strait for the same good reasons as they went for Rumoi, avoiding La Perouse. Coastal defense forts let alone mines. I picture them trying to do the same sort of thing, find a port on the Western coast that's not had defenses against the projected U.S invasion emplaced.

Looking at how far they planned to go from Sahkalin & it's port to Rumoi leaves anywhere as south as Yurihonjo or Tsuruoka on Honshu within a similar range of the southern tip of Hokkaido.

This map - http://www.history.army.mil/books/wwii/MacArthur%20Reports/MacArthur%20V1/Images/p_122.jpg

prepared for downfall shows the only suitable lowland within the area, the Noshiro-Akita plain (the previous chapter notes how the Soviets felt the most advantageous timing for their entry would be post any American invasion of Kyushu). A previous substantive post by Chris S on areas mined seems to rule out anything south of Funakawa, as well as the fact that Funakawa which may also be called Oga today was home to Japans fourth 'Kaiten' (Kamikaze torpedo) training base.

Which leaves.. Noshiro.
http://fsfiles.org/flightsimshotsv2/images/2013/09/23/CrEav.jpg
(Ignore the jet, it's the only aerial representation of the Town I could find).
Modern day it's about twice the size of Rumoi. Port was present but had declined in economic importance due to silting until it was expanded post war.

This Northern portion of Taiho, Honshu which Noshiro is part of is within the Eleventh Area Army's zone of responsibility. http://en.wikipedia.org/wiki/Japanese_Eleventh_Area_Army

"It consisted mostly of poorly trained reservists, conscripted students and home guard militia."

All of the forces listed were either emplaced on the East Coast or the Eastern potion of Amori (far North, also listed in the base plan of an invasion of Japan & likely the area the U.S would switch to after intelligence concerning Kyushu, http://www.history.army.mil/books/wwii/MacArthur Reports/MacArthur V1/Images/p_129.jpg). The only division worth detailing, the 142nd is on the *not West - East sorry, what am I saying, dyslexic* & is listed as a coastal defense division, so there's likely inherent shortages of transportation.

Forces from Northern/Western Honshu were listed as having already been diverted to the Nagoya & Kanto regions and that more would be diverted in the event of an invasion of those areas (Kanto - Coronet).

The sixth of October & the third of November are moonless periods which favour parachute drops.

 

[The Red]

The sixth of October & the third of November are moonless periods which favour parachute drops.

Could the Soviets prepare a naval/aerial assault in just one month though, presuming resistance in Hokkaido ends in late September? And is it particularly attractive when there are still large Japanese forces which could potentially counter attack? An assault just before Coronet is due might make more sense, still beating the Americans to Honshu but with a short enough window before the inevitable Japanese collapse to ensure a lack of significant casualties.

 

[Curiousone]

Could the Soviets prepare a naval/aerial assault in just one month though, presuming resistance in Hokkaido ends in late September? And is it particularly attractive when there are still large Japanese forces which could potentially counter attack? An assault just before Coronet is due might make more sense, still beating the Americans to Honshu but with a short enough window before the inevitable Japanese collapse to ensure a lack of significant casualties.

The planned attack on Rumoi on the 22nd of August was to be a combined Naval/Air drop. Their operations weren't that large, they seemed to be able to switch what they were doing fairly quickly, OTL going to the Kurils instead of Rumoi, doing Korea one day, something else the next. The flexibility & rapidity of the Manchurian portion of the war is a good light to hold it up to.

With about six divisions in the Eleventh Area Army there won't be a 3-1 ratio of forces against the Soviets( 3 Marine, 1 Para) even if they can move everything in one co-ordinated piece & assuming their forces will match the invaders (note the 50th 'Army' was not only poorly trained etc but totally green). Not counting Air Superiority on the Soviet side.

They probably want to wait for the American landings but can't, those are delayed by Typhoons and logistics, Soviets probably can't take heavily prepared beaches, will need to move fast. They might be bottled up, river to the south, mountains to the north, fighting inland for a while. Then the Americans will land elsewhere, the Japanese collapse will come & it's logistics that shape how fast & how far they can get.

The more I look at it the more the Japanese decision to surrender when they did looks like a good one.

 

[The Red]

They might be bottled up, river to the south, mountains to the north, fighting inland for a while.

That might suit them just fine however, land, occupy the lowlands, then hold that sliver of territory until things unravel. What matters is that they're on Honshu, and if they choose to advance even further, when things properly collapse in the Spring of 1946, it's going to be hard not to recognise that fact in a post-war settlement.

 

[zeppelinair]

hi curiousone, the red and many others who have helped embellish this thread!
curiousone: hope you soon finish that long post you wanted to post here, I'm most interested in the details of what you have to add for the Soviet invasion of Japan.
many other ppl: thanks so much for your contributions! please continue this thread going and help other ppl get ideas!
I'm writing this because the knowledge we talk of right now is beyond anything I have heard of...

 

[Curiousone]

hi curiousone and many others who have helped embellish this thread!
curiousone: hope you soon finish that long post you wanted to post here, I'm most interested in the details of what you have to add for the Soviet invasion of Japan.
many other ppl: thanks so much for your contributions! please continue this thread going and help other ppl get ideas!
I'm writing this because the knowledge we talk of right now is beyond anything I have heard of...

Mostly I'd already re-written it.

There's this - http://militera.lib.ru/research/suvorov6/03.html detailing how the para drops in Manchuria weren't even by regular airborne troops but 'special reconnaissance'/Spetznaz themselves, seizing railroad tunnels, airfields, landing with a high ranking officer & fooling large Japanese units into thinking they were surrounded, taking their surrender.

And some rambling thoughts on what kind of logistics it'll take just to supply the invasion zone..

This list detailing Soviet Merchant losses in the Pacific, http://www.shipsnostalgia.com/guide...Pacific)#PACIFIC_AND_INDIAN_OCEANS_IN_DETAILS

23 Ships, 83,000TN. Average tonnage per ship.. about 4,000.

This details the Soviet Pacific Merchant Marine under 'FESCO' - Far Eastern State Shipping Company.
http://www.kscnet.ru/ivs/bibl/paperno/for_65_engl.htm

They had 85 vessels in 1941, bought
27 in 1942,
46 in 1943,
20 in 1944
35 in 1945 (lets call it 20 since we're only part way through 1945.

So.. 85+27+46+20+20-23 = 175 ships. 175 x 4,000 tonnes = about 700,000 tonnes of shipping capacity in the Pacific. That jives well with this - http://www.globalsecurity.org/military/world/russia/morflot-sov.htm
which put total Soviet merchant capacity at 2.5 million tonnes in 1945. There were also other vessels put into service for transport (anything & everything, trawlers etc).

Of that you have to ask what they can spare/re-organize in time for Vladivostok - Noshiro runs, what the port at Noshiro is going to be able to handle while the amphibious transports land supplies over the beach. I'm guessing the limitation is going to be in just what the port at Noshiro can handle. There's six berths in the modern port, 3-4 of which handle only up to 5,000 tonne ships, are probably the limit of what was there before the expansion post-war OTL.

It's very rule of thumb but here's an example of what an infantry division is going to require in terms of supples:

http://www.mnstarfire.com/ww2/history/land/division.html

For a German Infantry Division, in heavy fighting 1,100 tonnes a day was needed.
A Soviet Division will have half the men, less equipment.

It takes about six times less time to load/unload ships with containerization as it did before it. It takes about 10-12 hours these days. So 3-4 docks, 4-5000 tonne goods tonnage; 12,000-20,000 tonnes/4 or more days = 3-5000 tonnes a day unloaded. If everything goes well. So perhaps six extra divisions can be sent beyond the 3 marine, 1 paratrooper after the port gets up and running properly. I could be way off.

 

[Chris S]

Ahh wrote a long post & then accidentally shut the tab, frustration.



Is it too big an assumption to have Stalin as unconcerned about casualties, having land-grabbing motives (for at least what he can bargain in concessions for it later)?




I don't see the Soviets invading via the Tsushima strait for the same good reasons as they went for Rumoi, avoiding La Perouse. Coastal defense forts let alone mines. I picture them trying to do the same sort of thing, find a port on the Western coast that's not had defenses against the projected U.S invasion emplaced.

Looking at how far they planned to go from Sahkalin & it's port to Rumoi leaves anywhere as south as Yurihonjo or Tsuruoka on Honshu within a similar range of the southern tip of Hokkaido.

This map - http://www.history.army.mil/books/wwii/MacArthur%20Reports/MacArthur%20V1/Images/p_122.jpg

prepared for downfall shows the only suitable lowland within the area, the Noshiro-Akita plain (the previous chapter notes how the Soviets felt the most advantageous timing for their entry would be post any American invasion of Kyushu). A previous substantive post by Chris S on areas mined seems to rule out anything south of Funakawa, as well as the fact that Funakawa which may also be called Oga today was home to Japans fourth 'Kaiten' (Kamikaze torpedo) training base.

Which leaves.. Noshiro.
http://fsfiles.org/flightsimshotsv2/images/2013/09/23/CrEav.jpg
(Ignore the jet, it's the only aerial representation of the Town I could find).
Modern day it's about twice the size of Rumoi. Port was present but had declined in economic importance due to silting until it was expanded post war.

This Northern portion of Taiho, Honshu which Noshiro is part of is within the Eleventh Area Army's zone of responsibility. http://en.wikipedia.org/wiki/Japanese_Eleventh_Area_Army

"It consisted mostly of poorly trained reservists, conscripted students and home guard militia."

All of the forces listed were either emplaced on the East Coast or the Eastern potion of Amori (far North, also listed in the base plan of an invasion of Japan & likely the area the U.S would switch to after intelligence concerning Kyushu, http://www.history.army.mil/books/wwii/MacArthur Reports/MacArthur V1/Images/p_129.jpg). The only division worth detailing, the 142nd is on the *not West - East sorry, what am I saying, dyslexic* & is listed as a coastal defense division, so there's likely inherent shortages of transportation.

Forces from Northern/Western Honshu were listed as having already been diverted to the Nagoya & Kanto regions and that more would be diverted in the event of an invasion of those areas (Kanto - Coronet).

The sixth of October & the third of November are moonless periods which favour parachute drops.

The thing is that after the Soviets land on Hokkaido, the Japanese will probably either surrender to the Allies to avoid a repeat happening in Honshu OR if some kind of military takeover has come into effect and the Emperor is effectively cut off from the military command (perhaps not with a takeover or a coup in the normal sense but with the Emperor evacuated to the redoubt in the mountains near Matsushiro and from there being cut off from communicating with the military) and the Japanese military high command decided to continue fighting then they are unlikely to leave northwestern Honshu undefended. It is quite likely that they would shuffle forces around to ensure that the Noshiro-Akito plain and other parts of northern Honshu are actually covered by some amount of defensive forces. Of course this would suit American purposes as it would mean that Japanese forces that were intended to reinforce the Kanto Plain and Kyushu end up getting diverted northwards...

 

[Curiousone]

The thing is that after the Soviets land on Hokkaido, the Japanese will probably either surrender to the Allies to avoid a repeat happening in Honshu OR if some kind of military takeover has come into effect and the Emperor is effectively cut off from the military command (perhaps not with a takeover or a coup in the normal sense but with the Emperor evacuated to the redoubt in the mountains near Matsushiro and from there being cut off from communicating with the military) and the Japanese military high command decided to continue fighting then they are unlikely to leave northwestern Honshu undefended. It is quite likely that they would shuffle forces around to ensure that the Noshiro-Akito plain and other parts of northern Honshu are actually covered by some amount of defensive forces. Of course this would suit American purposes as it would mean that Japanese forces that were intended to reinforce the Kanto Plain and Kyushu end up getting diverted northwards...

Yes.. there's only so many places the Japanese can cover. A Soviet invasion of Hokkaido can speed up American timetables as well - if they allow American airbases there, there's no need for a preliminary Kyushu landing to provide airbases for an attack on Kanto. The Soviets emphasized speed & shock in Manchuria.. it's a wonder if the Japanese were late in planning for Downfall & countering a potential invasion of Hokkaido OTL how they would have done later on ITTL.

Whether transport allows the Japanese to move substantive forces in time is really a question. The Americans were going to have smashed the railways in late August, if they shift the invasion site to Sendai or Mushu they'll no doubt be hitting the railways of N/Honshu hard on top of it. OTOH if they do go for Kanto units everywhere else are going to be sent there.

Troops they can possibly move.. but the heavy stuff, coastal guns/fortification material? The Soviets did manage to take Shumshu (http://en.wikipedia.org/wiki/Battle_of_Shumshu) against an equal number of troops plus some tanks, spattering of coastal artillery. N.b, with no Air Support until the afternoon when the weather cleared.

Might make it more of a fight at least. Key for the Soviets is not losing too many irreplaceable LCI(L) landing craft & capturing the docks in one piece.

Wish there was some kind of simulator to work with/one of those old tabletop foldout wargames with a scenario sketched out.

And yeah, continued war does seem to require the Military running the show in Japan.

 

[The Red]

A Soviet invasion of Hokkaido can speed up American timetables as well - if they allow American airbases there, there's no need for a preliminary Kyushu landing to provide airbases for an attack on Kanto.

Stalin likely wouldn't offer, and Truman likely wouldn't ask, as the price would likely be recognising the Soviet right to a occupation zone on Honshu.