WI: Japanese retained the 9th division in Okinawa until April 1945

[trurle]

What if: Japanese retained the 9th division in Okinawa until April 1945.
https://en.wikipedia.org/wiki/9th_Division_(Imperial_Japanese_Army)

Background: Japanese on main Okinawa island had effectively 3 divisions (24th division full strength, 2 regiments of 62nd division, small elements of 28th division, 44th mixed independent brigade), reinforced by 5th artillery group (comprising ~120 field guns, 96 medium mortars, 54 ATGs, ~160 AA guns).

IOTL, in Battle of Okinawa US army had 101 thousand casualties (including psychiatric) of 183 thousands of initial invasion force.

Throw the 9th IJA division (by the way, elite one, unlike the troops defending Okinawa IOTL) in the mix, and the situation become quite contentious.
The answers to questions/plausibility comments are welcome:
1) Will the Okinawa invasion be cancelled in favour of some easier target?
2) Possible more successful Japanese counterattacks? Outright invasion failure?
3) Longer Japanese resistance extends into peak typhoon season of July-October, resulting in supply problems for US troops?
https://en.wikipedia.org/wiki/Typhoon#Frequency
4) Nuclear bomb used tactically on Okinawa (or other target?)instead of Hiroshima+Kitakyushu (rerouted to Nagasaki IOTL because of unexpected overcast) bombing?
5) Any other consequences?

 

[galveston bay]

Okinawa was vital for Operation Downfall and particularly Operation Olympic, so the operation goes ahead.

Based on how the Japanese fought the battle, I would simply expect a stronger counterattack that still fails catastrophically. The Japanese Army was hard to dig out, but when it came out where it could be targeted, American firepower was simply too overwhelming.

Very likely longer resistance, which would see Buckner sacked if he wasn't killed (as in OTL), but probably broken by July at the latest. A massive typhoon did actually hit Okinawa by the way in October.

Perhaps the battle is costly enough so that Marshal and Truman decide that their misgivings are big enough to cancel Olympic. That was seriously considered as both of them had misgivings about Macarthurs rosy intelligence outlook for Kyushu, and when the real numbers of what the Japanese had sent there became apparent in July, Marshall begin talking about possible options. It would strengthen the case of the Navy (blockade) and Lemay (keep bombing). Of course that means a Japanese famine if the atomic bombs don't bring them to the table

nuclear weapons would not have been used on Okinawa... they were being saved for their shock value (which they indeed had)

 

[trurle]

I had nearly the same forecast, although with the Japanese resistance stretching to 20th of July.
Other opinions?

 

[Carl Schwamberger]

I consider Col Yaharas account of the battle a must read. Much of what we understand of the battle is drawn indirectly from the interrogation of Yahara & reading his post war description is useful. (Note: Col Yahara was the operations officer for the Japanese 10th Army. He was captured late summer attempting to escape the island.)

...
Based on how the Japanese fought the battle, I would simply expect a stronger counterattack that still fails catastrophically. The Japanese Army was hard to dig out, but when it came out where it could be targeted, American firepower was simply too overwhelming.

There was pressure from the more fanatical or optimistic officers to make such a attack/s earlier. The strategy for trying to inflict maximum casualties by remaining on the defense was not universally accepted. They wanted to take the offensive in tandem with the air and naval counter attacks.

Very likely longer resistance, which would see Buckner sacked if he wasn't killed (as in OTL), but probably broken by July at the latest. A massive typhoon did actually hit Okinawa by the way in October.

...

Alternately Buckner might see the problem in the frontal attacks vs fortifications and take the suggestions to flank the Shuri Line. Depends on how effective his intel section was & if his deputy Geiger had pushed for a flanking manuver harder.

 

[BobTheBarbarian]

The answers to questions/plausibility comments are welcome:
1) Will the Okinawa invasion be cancelled in favour of some easier target?
2) Possible more successful Japanese counterattacks? Outright invasion failure?
3) Longer Japanese resistance extends into peak typhoon season of July-October, resulting in supply problems for US troops?
https://en.wikipedia.org/wiki/Typhoon#Frequency
4) Nuclear bomb used tactically on Okinawa (or other target?)instead of Hiroshima+Kitakyushu (rerouted to Nagasaki IOTL because of unexpected overcast) bombing?
5) Any other consequences?

1. Okinawa was vital for providing air support for Operation Olympic in November 1945. It had to be taken at all costs no matter what the defenses were.

2. The Japanese counterattacks are moderately more successful, but still fail (they were operating at a 5 to 1 disadvantage in numbers vis-a-vis the 10th Army). Even with one more division it wouldn't have made much difference.

3. In my estimation the Japanese probably could have held for about another month or so with increased US casualties incident to such a fight (~30,000 casualties). The 9th Division, unlike the other two present on Okinawa, was an elite formation from the original Kwantung Army.

Alternately Buckner might see the problem in the frontal attacks vs fortifications and take the suggestions to flank the Shuri Line. Depends on how effective his intel section was & if his deputy Geiger had pushed for a flanking manuver harder.

IOTL this was considered but rejected. Buckner believed the strength of Japanese firepower and the rugged terrain of southern Okinawa would have made any such landing like "another Anzio, but worse." Little did he know Ushijima and his staff feared that such a move might have the potential to compromise the Shuri Line.

 

[Carl Schwamberger]

...

IOTL this was considered but rejected. Buckner believed the strength of Japanese firepower and the rugged terrain of southern Okinawa would have made any such landing like "another Anzio, but worse." Little did he know Ushijima and his staff feared that such a move might have the potential to compromise the Shuri Line.

I'd like to see the actual intel reports US 10th Army staff were working from. The proposed flank manuver was not universally rejected among Buckners staff.

...
Buckner believed the strength of Japanese firepower and the rugged terrain of southern Okinawa would have made any such landing like "another Anzio, but worse." ....

Which kind of misses the problem of terrain & enemy fire power the Shuri line defense was based on. IIRC on of the counter arguments to a flank manuver was the Shuri line was about to collapse anyway & preparations for a flanking attack would delay the end of the battle.

 

[galveston bay]

I consider Col Yaharas account of the battle a must read. Much of what we understand of the battle is drawn indirectly from the interrogation of Yahara & reading his post war description is useful. (Note: Col Yahara was the operations officer for the Japanese 10th Army. He was captured late summer attempting to escape the island.) .

I have run across references to his account (it appears in the book "Hell to Pay") but I haven't read it myself yet.

 

[CalBear]

The presence of another division, especially of "elite" troop might have been WORSE for the IJA. As has been noted the presence of additional troops might well have made the prospect of a counter-offensive too powerful to resist.

The Americans were near to praying that the Japanese would attack rather than remain in some of the best designed defense of the entire war. The Japanese come out into the open and the Americans have more than enough firepower afloat to destroy an entire Army (not including the 500 aircraft on the CVE, just the gun line, with 10 old BB, 11 CA/CL and 30 DD). There was literally no place above ground on the island that was safe from naval gunfire.

The key to the above is "above ground". Inside the defenses the IJA troops were relatively secure from anything but near direct hits. If they come out, they are meat on the table.

Good solid highly motivated counter-attack might have reduced the battle by at least a month. Always better to buy wholesale than pay retail.

 

[Carl Schwamberger]

I have run across references to his account (it appears in the book "Hell to Pay") but I haven't read it myself yet.

A larger translation (complete?) of his account can be found under the title 'The Battle for Okinawa'. This is the Robert Pineau/Masatoshi Uehara translation. A short 245 pages of text & appendices/index in my paperback.

One of the overlooked points Yahara raises is the relatively large number of Japanese soldiers who surrendered. Over 5% of the regular Army survived the battle vs less than 1% in themany other island battles. Yahara suggests discipline broke down in the last few days & a the survivors took the opportunity to NOT die for the emperor since there were few NCOs & fewer officers to enforce that aspect of their loyalty.

 

[trurle]

The presence of another division, especially of "elite" troop might have been WORSE for the IJA. As has been noted the presence of additional troops might well have made the prospect of a counter-offensive too powerful to resist.

The Americans were near to praying that the Japanese would attack rather than remain in some of the best designed defense of the entire war. The Japanese come out into the open and the Americans have more than enough firepower afloat to destroy an entire Army (not including the 500 aircraft on the CVE, just the gun line, with 10 old BB, 11 CA/CL and 30 DD). There was literally no place above ground on the island that was safe from naval gunfire.

The key to the above is "above ground". Inside the defenses the IJA troops were relatively secure from anything but near direct hits. If they come out, they are meat on the table.

Good solid highly motivated counter-attack might have reduced the battle by at least a month. Always better to buy wholesale than pay retail.

Japanese have made a large counter-attack twice on Okinawa. Afterward, commanders silly enough to advice such an attack were outnumbered and/or outranked. To shorten the battle by adding troops to Japanese, CalBear must solve the challenge of mass-killing Japanese, giving a preference to killing moderate (as opposed to suicidally-behaving) commanders. The larger percentage of inadequate (or outright senile) commanders in 9th division will help in this task though.

 

[galveston bay]

A larger translation (complete?) of his account can be found under the title 'The Battle for Okinawa'. This is the Robert Pineau/Masatoshi Uehara translation. A short 245 pages of text & appendices/index in my paperback.

One of the overlooked points Yahara raises is the relatively large number of Japanese soldiers who surrendered. Over 5% of the regular Army survived the battle vs less than 1% in themany other island battles. Yahara suggests discipline broke down in the last few days & a the survivors took the opportunity to NOT die for the emperor since there were few NCOs & fewer officers to enforce that aspect of their loyalty.

that I have seen, and it was noted in "Soldiers of the Sun' as well. Particularly in the Soviet conquest of Manchuria and Korea. For that matter prisoner counts were going up in the Philippines too (obviously not on the same scale as Manchuria).

I will have to look for that book though. I haven't read a good one on Okinawa in a while.

 

[Carl Schwamberger]

In these PoW counts you have to separate the non Japanese combat units & auxilliaries from the 'real' Japanese soldiers. The Manchurian army fought more like a Chinese or western army & would surrender or retreat when the situation became difficult, vs the Japanese Kwantung army which were more stubborn. On Okinawa when the militia are counted desertion and surrender accounted for well above 25% of the total on the muster rolls.

To digress. A old friend of mine, late Earl Kerhberg, was a radar tech in the Marine air wing on Okinawa when the battle ended. A day or two after the fighting halted a pair of Japanese soldiers walked out of the brush & fell in on the end of the line for breakfast. When interrogated it was found they had been hanging out around the squadrons camp for over a day, and ... wait for it...


..they had wandered through the camp during the evening & sat in on the movie shown near the mess area.

So no. Not every Japanese soldier was a suicidal fanatic.

 

[SactoMan101]

If the IJA 9th Division was there to defend Okinawa, the battle for that island would be FAR bloodier--probably double the toll on both sides in the OTL.

That would have forced a change in tactics for Operation Downfall--including a much larger invasion for Coronet, the invasion of Kyushu. And Kyoto goes right back on the list of targets for the atomic bomb. And an intensified strategic bombing campaign, maybe including B-17's and B-24's operating out of Okinawa (bombing western Japan) and maybe even near Vladivostok (bombing northern Japan).

 

[galveston bay]

If the IJA 9th Division was there to defend Okinawa, the battle for that island would be FAR bloodier--probably double the toll on both sides in the OTL.

That would have forced a change in tactics for Operation Downfall--including a much larger invasion for Coronet, the invasion of Kyushu. And Kyoto goes right back on the list of targets for the atomic bomb. And an intensified strategic bombing campaign, maybe including B-17's and B-24's operating out of Okinawa (bombing western Japan) and maybe even near Vladivostok (bombing northern Japan).

the Japanese toll wouldn't be double because the 9th would only add around 10-20,000 men to the total, and as is the Japanese casualties were effectively total. American casualties would have been far heavier, but not double either. But certainly higher and enough to make everyone (except maybe Macarthur) seriously consider whether Operation Olympic was realistic

There would not have been US bombers operating out of Soviet territory. The 8th Air Force was already en route to the Pacific and was to start operations in September and October, so no real change there.

 

[TFSmith121]

There's also the point that the OP's US casualty figures

the Japanese toll wouldn't be double because the 9th would only add around 10-20,000 men to the total, and as is the Japanese casualties were effectively total. American casualties would have been far heavier, but not double either. But certainly higher and enough to make everyone (except maybe Macarthur) seriously consider whether Operation Olympic was realistic

There would not have been US bombers operating out of Soviet territory. The 8th Air Force was already en route to the Pacific and was to start operations in September and October, so no real change there.

There's also the point that the OP's US casualty figures include, as far as I can make out, the naval casualties along with those of the 10th Army.

So unless an extra IJA infantry division somehow leads to additional IJNAF and IJAAF aircraft being dedicated to the operations around Okinawa, it's not going to have much of an impact there.

Best,

 

[mattep74]

Are we sure that the 9th would gladly stay in a defensive formation. Was there room for them, supplies? Maybe they try to stop the Americans on the beach(and gets destroyed in the process)

 

[BobTheBarbarian]

Are we sure that the 9th would gladly stay in a defensive formation. Was there room for them, supplies? Maybe they try to stop the Americans on the beach(and gets destroyed in the process)

Yes. Ushijima's goal was to create a defense in depth that would tie down as many American assets for as long as possible in order to buy time for preparations on the mainland. He knew he had nowhere near enough men or materiel to try and cover the beaches and defend the rear areas, or even cover the entire island. Instead, his 32nd Army hunkered down in the southern part of Okinawa (where everything important was located) and waited for the Americans to come to him.

 

[CalBear]

Are we sure that the 9th would gladly stay in a defensive formation. Was there room for them, supplies? Maybe they try to stop the Americans on the beach(and gets destroyed in the process)

We can be sure that they would be ordered to stay in a defensive position. We can't be sure they would, or tat all the composite units would.

IJA field grade officers were not nearly as obedient to superiors as their counterparts in the British, German or U.S. Armies, and not even in the same state as Red Army officers (Soviet field grade officers wouldn't even question an order, much less disobey one). The problem was actually worse with the more elite and better trained formations than with "scrubs". The top guns were so dedicated to the perverted version of Bushido that emerged in the 1930s that they would assassinate superior officers who they thought were insufficiently "pure".

 

[BobTheBarbarian]

We can be sure that they would be ordered to stay in a defensive position. We can't be sure they would, or tat all the composite units would.

I don't think this would have been so much of a problem. Any time something like this happened it was a relatively local, small-scale affair, such as the few unauthorized counterattacks on Iwo Jima. Generally speaking IJA troops were disciplined enough so as to not disobey the orders of their superiors. Even the 'fire-eaters' on Okinawa (the aggressive faction led by General Cho, himself a veteran of the China front and partially responsible for the Nanking massacre) didn't try anything unless they got Ushijima's permission first.

IJA field grade officers were not nearly as obedient to superiors as their counterparts in the British, German or U.S. Armies, and not even in the same state as Red Army officers (Soviet field grade officers wouldn't even question an order, much less disobey one). The problem was actually worse with the more elite and better trained formations than with "scrubs". The top guns were so dedicated to the perverted version of Bushido that emerged in the 1930s that they would assassinate superior officers who they thought were insufficiently "pure".

That sounds wildly exaggerated. Give one instance in which Japanese soldiers in the midst of a battle mutinied against and killed a superior officer for being 'too cautious.' There were frequent ill-feelings towards protracted defensive fighting, yes, but almost never outright rebellion. Such a thing usually only happened in peacetime or in 'behind the scenes' dramas in which matters of national policy were being settled, not battlefield tactics.

 

[Carl Schwamberger]

Are we sure that the 9th would gladly stay in a defensive formation. Was there room for them, supplies? Maybe they try to stop the Americans on the beach(and gets destroyed in the process)

My guess is they would be used to add depth to the defense. perhaps some intermeadiate delaying positions north of the Shuri Line. Once behind that line they could be used to guard the flanks/rear, or in local counter attacks.