How would the Japanese have resisted a American/Soviet invasion?

The estimate for the subs means they each sink 2.5 ships. Not happening, the USA had lots of escorts, and they were quite good at ASW. At this point, even if the Japanese could fuel all those subs, they had very few experienced officers and crew left. Bigger threats were the kamikaze speedboats and the manned torpedoes launched from the beach...there were caves that had movable rails to launch them, then pull back rails to hide.
 

CalBear

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Which would be bloodier Olympic or Coronet?
Probably Olympic. The Japanese were going to throw pretty much everything in the envelope at the Kyushu landings. The U.S. casualties in the period of D-1 to D+3 would likely have exceeded 100K, especially if the Kamikaze pilots managed to follow instructions hand ignore warships and strike at the transports & LST. Japanese losses would be around 100,000 KIA, possibly more, depending on how much of the militia actually turned out and how many civilians didn't get out of the landing zones before they started getting shelled.

Coronet is something of a mystery, not in the plans, but in what, if anything, the IJA would have left in the hopper. The U.S. was going to continue to pound the hell out of Honshu with heavy bombers while Olympic was taking place. The number of super heavy squadrons was going to more than double by the time Olympic was scheduled (the 8th AF was scheduled to start B-29 operations in early September out of Okinawa, a move that would have allowed for all of Honshu and Hokkaido, which had, until then, been outside of the range of Tinian based bombers, to be targeted. Just that change would have resulted in ever increasing material losses as previously "safe" supply locations would become vulnerable. The Japanese intended to expend nearly all the 10,000+ kamikaze in inventory against Olympic, as well as everything left of the surface fleet and all the surviving ocean going submarines. There would also be the near irresistible tendency to want to reinforce the Kyushu forces if they were doing better than expected.

A couple notes regarding some of the other posts -

The Japanese were well aware of how vulnerable their tunnels were vulnerable to flame thrower equipped tanks, heavy SP guns, and aircraft rockets. A considerable effort was made, starting with Saipan, to locate defensive positions where they were sheltered from these sorts of attack by terrain or through construction of dog-leg entrances. These efforts made it necessary to dig the defenders out the old fashioned way (probably best illustrated by the trouble the Shuri Line offered on Okinawa.

The Japanese battle plan was to extract maximum casualties. A critical part of this was the expectation that the U.S. would follow the same plan and absorb massive losses. That was unlikely. The U.S. intended to use nuclear weapons in a "tactical" role (at least six were earmarked just for the opening phase of Olympic), just the heat pulse of a weapon would be enough to literally roast defenders under cover and kill those above ground with both blast and debris, providing a 500-750 yard cleared zone. Most critically, had the Japanese begun to extract the sort of casualties they hoped for it is close to a given that Truman would have allowed the use of chemical weapons. Unlike the potential for use in the ETO, or even earlier in the Pacific War, the scenario during Downfall was very positive for use, primarily because the potential for Japanese reply in kind was, by late 1945, almost non-existent. The belief of the Japanese that the stronger they resisted the better the final terms would become is simply in error. What would have happened is that the U.S. would have done whatever was necessary to reduce American losses, the impact on the Japanese be damned.
 
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CalBear

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What other "innovations" did they have in their beach plan?

...
The other primary weapons were going to be the suicide speedboats, human torpedoes, and the previously unseen Ohka Model 43 B (the manned cruise missile designed to launch from caves), along with the more conventional bottom mines and command detonated mines. The speedboats and human torpedoes would have suffered incredible losses (98% is not unreasonable) but the Japanese had 9,000 of the Shin yo speed boats available (around 400 were used off the Philippines and Okinawa, they managed to sink 8 landing support ships/large landing craft, cripple a transport and knock a Fletcher class DD out of the war. Extrapolating those figures gives you a couple hundred successful strikes (even if they are all against LCI, that is around 8,000 KIA, just from the speedboats, they get a few transports or DD/DDE and that starts to jump really quickly).

A Wiki page on the suicide swimmers: https://en.wikipedia.org/wiki/Fukuryu

How many bombers did the 8th AF have?
When it first stood up in the Pacific it would have had around 200, which would have increased over the next couple months to around 600. It would literally have come close to tripling the number of aircraft available for operations over Japan. Eventually it would have deployed around 5 Bomber Groups

It was also bringing three fighter groups with late model P-47N. The effort was quite literally going to replicate the U.S. effort in the Combined Bomber offensive in Europe on Okinawa, but with B-29s replacing the B-17s and B-24s.
 
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trurle

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The estimate for the subs means they each sink 2.5 ships. Not happening, the USA had lots of escorts, and they were quite good at ASW. At this point, even if the Japanese could fuel all those subs, they had very few experienced officers and crew left. Bigger threats were the kamikaze speedboats and the manned torpedoes launched from the beach...there were caves that had movable rails to launch them, then pull back rails to hide.
The number of 500 sunk vessels unclude all Japanese subs, not just Kairyu class. By the way, historical records shows average Japanese sub performance 1.89 ships sunk per submarine lost, so 2.5 kills/submarine is in reasonable range. About kamikaze speedboats: Japanese army was very sceptical about them. Too vulnerable too anything including machine gun fire. To the point what during battle of Okinawa majority of kamikaze speedboat formations were disbanded, and crews were transferred to infantry. Assuming the same 18 men/hit effect as with kamikaze planes, suicide speedboat kill ratio was about 0.36 US/Japan - better than light infantry without support (which scored kill ratio of 0.1) but worse than nearly everything else. About recoilless weapons: do not forget what recoilless ammunition of era was 2-3 times heavier compared to standard artillery cartridges. Wide use of recoilless guns by US will give Japanese what they wanted - a lot of vulnerable targets to kill (supply companies etc). Realistically, greatest threat to the Japanese mountain artillery was the US 155 mm Long Tom counter-battery guns, which were used to deadly effect in Italia too.
 
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I'm not disputing your data - however that number is for the entire war. It does not reflect the situation in late 1945 when Olympic would happen. At that point in time the majority of Japanese subs other than small coastal ones had been sunk. while the invasion fleets would be in a limited area, so easy to "find" they would be surrounding by experienced ASW ships dedicated to keeping them safe, and the Japanese with few exceptions would not be experienced ships and crews with combat time. Would there be successes, of course, but you'll see way less than 1 ship per sub sunk here.
 

CalBear

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The number of 500 sunk vessels unclude all Japanese subs, not just Kairyu class. By the way, historical records shows average Japanese sub performance 1.89 ships sunk per submarine lost, so 2.5 kills/submarine is in reasonable range. About kamikaze speedboats: Japanese army was very sceptical about them. Too vulnerable too anything including machine gun fire. To the point what during battle of Okinawa majority of kamikaze speedboat formations were disbanded, and crews were transferred to infantry. Assuming the same 18 men/hit effect as with kamikaze planes, suicide speedboat kill ratio was about 0.36 US/Japan - better than light infantry without support (which scored kill ratio of 0.1) but worse than nearly everything else. About recoilless weapons: do not forget what recoilless ammunition of era was 2-3 times heavier compared to standard artillery cartridges. Wide use of recoilless guns by US will give Japanese what they wanted - a lot of vulnerable targets to kill (supply companies etc). Realistically, greatest threat to the Japanese mountain artillery was the US 155 mm Long Tom counter-battery guns, which were used to deadly effect in Italia too.
Actually the biggest danger to the mountain artillery was this

m-4328.jpg


While the CA and BB could lay in heavier shells and tear the hell out of bunkers, there was nothing the U.S. had that could match the Brooklyn and Cleveland class CL. Each gun could fire 8-10 RPM (on trials the USS Savannah fired 138 rounds in one minute, that was with a green crew) with remarkable accuracy.
 

Towelie

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It would be waterline, I expect. The deep defense strategy was one that was more effective but it was an admission of defeat, not an option on home soil. The casualties would be grievous for both sides, of course. I think the US would easily see 150K casualties in taking Kyushu, where the resistance would be worst, the Japanese probably somewhere around at least 600K KIA.

The question of course comes with the idea of mass suicides. Do they happen? It is one thing to get a bunch of villagers on Saipan to jump off cliffs with guns at your back, but it is another entirely to get hundreds of thousands of Kyushans to off themselves when defeat becomes clear, as it would be.

I think surrender would come sooner than some thought. The A-Bombs were bad, but the real reason to surrender was that the loss of raw materials in Manchuria and the destruction of Japanese rule in Korea, which would happen at the end of September probably would make it clear that things were irrevocably lost.
 

trurle

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While the CA and BB could lay in heavier shells and tear the hell out of bunkers, there was nothing the U.S. had that could match the Brooklyn and Cleveland class CL. Each gun could fire 8-10 RPM (on trials the USS Savannah fired 138 rounds in one minute, that was with a green crew) with remarkable accuracy.
Did the US 6-inch/47 gun had an HE or fragmentation shells? I had the impression it used only AP and APHE as typical for the majority of the big naval guns of the period. Wait..i see the Mk 34 AA shell, and with a proximity trigger. Yes, it would make a terrible hits against soft targets.
 

trurle

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http://www.ww2pacific.com/suicide.html

Here is a good link about some of the desperate measures were taking in defense of the home islands.
Most of these measures were not expected to be really effective. On the other hand, Kairyu submarines could be extremely deadly as shown by operation record of their German equivalent - Seehund class. The main problem was the submarine small size reducing the sonar and hydrophone detection range well below the guaranteed torpedo hit range.
 
Also, there's the question what the Japanese would do with the several hundred thousand allies POWs. Would they have used them as hostages?
 
Also, there's the question what the Japanese would do with the several hundred thousand allies POWs. Would they have used them as hostages?
https://en.wikisource.org/wiki/Kill_All_Prisoners_Order
Whether they are destroyed individually or in groups, or however it is done, with mass bombing, poisonous smoke, poisons, drowning, decapitations, or what, dispose of them as the situation dictates.

In any case it is the aim not to allow the escape of a single one, to annihilate them all, and not to leave any traces.
 
Basically all the Allied prisoners, wherever they were, were to be killed as soon as the first Allied soldiers set foot on Japanese soil. It's not entirely clear, but the odds are good that the many Allied civilian detainees, including women and children would probably meet the same fate. This could not be hidden as there were recon flights over known POW camps with some regularity, needless to say learning that POWs and potentially civilians were being slaughtered would result in whatever limitations Allied governments felt or individual soldiers would have had will go by the wayside. If this happened the advance of the Allies in Japan would make Mongol conquests look like a child's tea party.

The Americans could manufacture enough poison gas of various kinds to blanket Japan, and essentially all of the civilian population and most of the military would be defenseless. Even the few military personnel who have protection will soon be in trouble, as replacement canisters for their gas masks will be in short supply.
 
It would be a huge decimation of Japanese civilians and soldiers once all those POWs are killed. The Japanese worst predictions may well come true.
 
the real reason to surrender was that the loss of raw materials in Manchuria and the destruction of Japanese rule in Korea

Which makes me wonder, if the Pacific had gone faster than Europe (for whatever reason) and the US had been ready to invade Japan before the Soviets could help with Manchuria and Korea, how things might have gone. (And would the US have attempted to invade mainland Asia before Japan?)

fasquardon
 

Towelie

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Which makes me wonder, if the Pacific had gone faster than Europe (for whatever reason) and the US had been ready to invade Japan before the Soviets could help with Manchuria and Korea, how things might have gone. (And would the US have attempted to invade mainland Asia before Japan?)

fasquardon
The Japanese High Command knew that the war was lost after Saipan. What happened afterwards was basically a coup of the ultra extremists in the Imperial General Staff and the resignation of the less hardline and more discredited officers like Tojo.

The decision to surrender came after a second failed coup of the extreme of the ultra hardliners. Basically, people who were too delusional for the delusional.

At any point in time, this could have fallen apart. An invasion of Japan might have drove home the stupidity of continued hostility or reinforced the hardliners. It is difficult to tell which would have happened. Japan could have kept up the struggle until the military conquest of Honshu or the loss of Manchuria, however.
 
Basically all the Allied prisoners, wherever they were, were to be killed as soon as the first Allied soldiers set foot on Japanese soil. It's not entirely clear, but the odds are good that the many Allied civilian detainees, including women and children would probably meet the same fate. This could not be hidden as there were recon flights over known POW camps with some regularity, needless to say learning that POWs and potentially civilians were being slaughtered would result in whatever limitations Allied governments felt or individual soldiers would have had will go by the wayside. If this happened the advance of the Allies in Japan would make Mongol conquests look like a child's tea party.

The Americans could manufacture enough poison gas of various kinds to blanket Japan, and essentially all of the civilian population and most of the military would be defenseless. Even the few military personnel who have protection will soon be in trouble, as replacement canisters for their gas masks will be in short supply.

Had Japan done so how much worse would the occupation and War trials been?
 
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