39 replies to this topic

[Inhapi]

I wonder what kind of tanks were planned to be included in the invading forces in operation downfall.

 

AFAIK at that time the us had switched  production to 76 mm variants (with low 75 mm production for allies) and the M 26 was becoming more prominent.

 

What was the state of US intelligence on Japense tanks in the home islands, what did they expect the japanese could field in any numbers (if at all).

 

I wonder wether the M 26 would have been useful given the terain.

 

I also wonder given the lack of more than a handful of well armed Japanese tanks, it would not have been better to revert to 75 mm guns on the  M4 ?

 

I guess the light tank units would be re armed completely with the M24.

 

What about the  M105 mm variants ? Were they going to deployed in greater numbers ?

 

Were flamethrowers to be used in greater numbers than before ?

 

thanks for any input.

 

Inhapi

 

[JasonJ]

I got no idea about the M4 105s.

 

Even though they switched to the 76 in production, there was probably still plenty of M4s of various kinds still armed with the 75mm available. But yeah, pretty sure others would thing that the 75mm would be more useful than the 76.

 

M18 hellcats were apparently used a little late in the Pacific War, in the Battle of Okinawa and/or at Luzon. So some of them probably could be expected to to be used for later operations.

 

As for US intelligence on the tank situation in Japan, I can't say from a position of having looked into much US WW2 intelligence documents, but up to August 1945, the only tanks that were in the combat zones were Chi-Ha with the 57mm, Chi-Ha Shinhoto, and the Ho-Ni 75mm 50 mm front superstructure but open top SPG and a similar design with a short 149.1mm called the Ho-Ro. So after battle analysis would provide no information about some of the various tanks kept in Japan such as the Chi-Nu. While only about 150 were produced, they were deployed to units and ready to go, some having been deployed to Kyushu. In defensive posture, these could fight on near equal terms with M4 75mm. Encounters with them would be the few times that an M26 would prove its worth since its armor should resists Chi-Nu's 75mmL36 quite well. One other engagement threshold the M26 armor would cross is its side armor. M4 side armor was still vulnerable to Japanese 47mm anti-tank guns but M26 side should resist that better. One more case where the M26 Pershings armor probably would prove advantageous over the M4's in resisting Japanese Type 4 70mm (technically 74mm) anti-tank rocket with its 80mm penetration ability at 60-90 degree angle. 3,500 of these were made with apparently 47,600 rounds.

[Inhapi]

I got no idea about the M4 105s.

 

Even though they switched to the 76 in production, there was probably still plenty of M4s of various kinds still armed with the 75mm available. But yeah, pretty sure others would thing that the 75mm would be more useful than the 76.

 

M18 hellcats were apparently used a little late in the Pacific War, in the Battle of Okinawa and/or at Luzon. So some of them probably could be expected to to be used for later operations.

 

As for US intelligence on the tank situation in Japan, I can't say from a position of having looked into much US WW2 intelligence documents, but up to August 1945, the only tanks that were in the combat zones were Chi-Ha with the 57mm, Chi-Ha Shinhoto, and the Ho-Ni 75mm 50 mm front superstructure but open top SPG and a similar design with a short 149.1mm called the Ho-Ro. So after battle analysis would provide no information about some of the various tanks kept in Japan such as the Chi-Nu. While only about 150 were produced, they were deployed to units and ready to go, some having been deployed to Kyushu. In defensive posture, these could fight on near equal terms with M4 75mm. Encounters with them would be the few times that an M26 would prove its worth since its armor should resists Chi-Nu's 75mmL36 quite well. One other engagement threshold the M26 armor would cross is its side armor. M4 side armor was still vulnerable to Japanese 47mm anti-tank guns but M26 side should resist that better. One more case where the M26 Pershings armor probably would prove advantageous over the M4's in resisting Japanese Type 4 70mm (technically 74mm) anti-tank rocket with its 80mm penetration ability at 60-90 degree angle. 3,500 of these were made with apparently 47,600 rounds.

 

Would the M26, being so underpowered and with its fautly transmission be able to move around enough to be useful in the hilly to mountainious Kyushu ?  Maybe having some of them to use in a traditional heavy tank role (eg breaking up heavy japanese fortifications ofr resistance points) would have made sense. But i guess due to mobility reasons the M4 (either 75 mm 76 mm 705 mm) would have been much more mobile.

 

Nice reading about the Hellcat, i can barely think of an AFV less suited for conditions in the Pacific. (but maybe its light weight made it more mobile in difficult terrain ,)

 

How about the M8 ? I know these were out of production at this time, but it seems to me a good light vehicle to bring quite some firepower to really inaccessible places.

[JasonJ]

 

I got no idea about the M4 105s.

 

Even though they switched to the 76 in production, there was probably still plenty of M4s of various kinds still armed with the 75mm available. But yeah, pretty sure others would thing that the 75mm would be more useful than the 76.

 

M18 hellcats were apparently used a little late in the Pacific War, in the Battle of Okinawa and/or at Luzon. So some of them probably could be expected to to be used for later operations.

 

As for US intelligence on the tank situation in Japan, I can't say from a position of having looked into much US WW2 intelligence documents, but up to August 1945, the only tanks that were in the combat zones were Chi-Ha with the 57mm, Chi-Ha Shinhoto, and the Ho-Ni 75mm 50 mm front superstructure but open top SPG and a similar design with a short 149.1mm called the Ho-Ro. So after battle analysis would provide no information about some of the various tanks kept in Japan such as the Chi-Nu. While only about 150 were produced, they were deployed to units and ready to go, some having been deployed to Kyushu. In defensive posture, these could fight on near equal terms with M4 75mm. Encounters with them would be the few times that an M26 would prove its worth since its armor should resists Chi-Nu's 75mmL36 quite well. One other engagement threshold the M26 armor would cross is its side armor. M4 side armor was still vulnerable to Japanese 47mm anti-tank guns but M26 side should resist that better. One more case where the M26 Pershings armor probably would prove advantageous over the M4's in resisting Japanese Type 4 70mm (technically 74mm) anti-tank rocket with its 80mm penetration ability at 60-90 degree angle. 3,500 of these were made with apparently 47,600 rounds.

 

Would the M26, being so underpowered and with its fautly transmission be able to move around enough to be useful in the hilly to mountainious Kyushu ?  Maybe having some of them to use in a traditional heavy tank role (eg breaking up heavy japanese fortifications ofr resistance points) would have made sense. But i guess due to mobility reasons the M4 (either 75 mm 76 mm 705 mm) would have been much more mobile.

 

Nice reading about the Hellcat, i can barely think of an AFV less suited for conditions in the Pacific. (but maybe its light weight made it more mobile in difficult terrain ,)

 

How about the M8 ? I know these were out of production at this time, but it seems to me a good light vehicle to bring quite some firepower to really inaccessible places.

 

 

Mobility is a fair point on M26. Much like how they struggled in Korea 5-7 years later. Perhaps in places like the Kanto plain or Osaka plain, the M26 probably wouldn't have too much difficulty, so yeah like you say, like traditional heavy tank makes sense to me.

 

I don't know why they put the M18 there. For the typical clash style against dug-in Japanese, good armor going at infantry pace seemed to make most sense rather than sending some high speed penetrating unit. But there's probably a reason for its inclusion.

 

I think M8s as open top and light armor are going to rather not expose them selves doing fire support.

 

Just my thoughts on it.

[nitflegal]

 

 

I got no idea about the M4 105s.

 

Even though they switched to the 76 in production, there was probably still plenty of M4s of various kinds still armed with the 75mm available. But yeah, pretty sure others would thing that the 75mm would be more useful than the 76.

 

M18 hellcats were apparently used a little late in the Pacific War, in the Battle of Okinawa and/or at Luzon. So some of them probably could be expected to to be used for later operations.

 

As for US intelligence on the tank situation in Japan, I can't say from a position of having looked into much US WW2 intelligence documents, but up to August 1945, the only tanks that were in the combat zones were Chi-Ha with the 57mm, Chi-Ha Shinhoto, and the Ho-Ni 75mm 50 mm front superstructure but open top SPG and a similar design with a short 149.1mm called the Ho-Ro. So after battle analysis would provide no information about some of the various tanks kept in Japan such as the Chi-Nu. While only about 150 were produced, they were deployed to units and ready to go, some having been deployed to Kyushu. In defensive posture, these could fight on near equal terms with M4 75mm. Encounters with them would be the few times that an M26 would prove its worth since its armor should resists Chi-Nu's 75mmL36 quite well. One other engagement threshold the M26 armor would cross is its side armor. M4 side armor was still vulnerable to Japanese 47mm anti-tank guns but M26 side should resist that better. One more case where the M26 Pershings armor probably would prove advantageous over the M4's in resisting Japanese Type 4 70mm (technically 74mm) anti-tank rocket with its 80mm penetration ability at 60-90 degree angle. 3,500 of these were made with apparently 47,600 rounds.

 

Would the M26, being so underpowered and with its fautly transmission be able to move around enough to be useful in the hilly to mountainious Kyushu ?  Maybe having some of them to use in a traditional heavy tank role (eg breaking up heavy japanese fortifications ofr resistance points) would have made sense. But i guess due to mobility reasons the M4 (either 75 mm 76 mm 705 mm) would have been much more mobile.

 

Nice reading about the Hellcat, i can barely think of an AFV less suited for conditions in the Pacific. (but maybe its light weight made it more mobile in difficult terrain ,)

 

How about the M8 ? I know these were out of production at this time, but it seems to me a good light vehicle to bring quite some firepower to really inaccessible places.

 

 

Mobility is a fair point on M26. Much like how they struggled in Korea 5-7 years later. Perhaps in places like the Kanto plain or Osaka plain, the M26 probably wouldn't have too much difficulty, so yeah like you say, like traditional heavy tank makes sense to me.

 

I don't know why they put the M18 there. For the typical clash style against dug-in Japanese, good armor going at infantry pace seemed to make most sense rather than sending some high speed penetrating unit. But there's probably a reason for its inclusion.

 

I think M8s as open top and light armor are going to rather not expose them selves doing fire support.

 

Just my thoughts on it.

 

For what its worth, I've had the chance to talk to several Korean war tankers and at least two have mentioned that their M4's were rather frequently used to drag Pershings out of mud and such.  I would expect similar things from them in much of the Japanese country as well.

[R011]

There were more HVSS Shermans made than Pershings so most of the tanks would have been them. As fighting went on, it is likely that some of the M26 would be replaced by M4. Depending on losses and availability, we might see VVS 75 mm armed tanks. Probably most of the flamethrower tanks would be those from the beginning.

Edit: As far as I can tell, a couple of thousand M4A3 (105) HVSS Shermans were made, so that might be enough for the six per tank battalion called for by late war TO&E.

Edited by R011, 12 November 2019 - 2026 PM.

[DougRichards]

Well as three British Commonwealth infantry divisions were earmarked for Coronet, it may be assumed that they would have been supported by a RAR Brigade of Churchills each.  Or around 500 tanks in total.  Well armoured, slow but reliable, able to deal with rough terrain and with sufficient armament to deal with Japanese tanks.  Throw in a number of Crocodiles and some Churchill AVRE with petards.  Perhaps put Hobart in charge of an extemporised Churchill equipped armour division. 

 

If things stalled in Downfall due to unsuitable armour, perhaps the British could have filled the gaps.

[Stuart Galbraith]

And the Bob Semple Tank, dont forget that....

[DougRichards]

And the Bob Semple Tank, dont forget that....

 

New Zealand units were not part of the order of battle.  Canadian, British and Australian were.

 

Remember that Churchill tanks were fairly successful in Korea.

[Inhapi]

Well as three British Commonwealth infantry divisions were earmarked for Coronet, it may be assumed that they would have been supported by a RAR Brigade of Churchills each.  Or around 500 tanks in total.  Well armoured, slow but reliable, able to deal with rough terrain and with sufficient armament to deal with Japanese tanks.  Throw in a number of Crocodiles and some Churchill AVRE with petards.  Perhaps put Hobart in charge of an extemporised Churchill equipped armour division. 

 

If things stalled in Downfall due to unsuitable armour, perhaps the British could have filled the gaps.

 

Yes i guess that a mix of Churchill Gun tanks, AVRE's and Crocodiles would have been ideal in Japan given the landscape and the opposition expected.

Edited by Inhapi, 13 November 2019 - 0758 AM.

[Stuart Galbraith]

 

And the Bob Semple Tank, dont forget that....

 

New Zealand units were not part of the order of battle.  Canadian, British and Australian were.

 

Remember that Churchill tanks were fairly successful in Korea.

 

 

I was joking Doug.

 

Bear in mind, the Kiwi's were part of the Commonwealth Armoured Division postwar. They even had their own squadron of Centurions.

[Ken Estes]

The Army had already unloaded M26s on Okinawa, after the fighting had ended. Their availability for the invasion of the Home Islands can be presumed. Light tanks might have had little if any employment. Ordnance Dept was offering the T-29 heavy tank and the 240mm SP  then in prototypes and new H5 flame tanks converted from M4 mediums but retaining the 75mm gun.

 

The USMC had enough M4 series tanks with 75mm for the first invasion, but c. 600 M4(105mm) would be available for the second. There was no interest in any 76mm armed mediums. The new LVT(A)-5 armored amphibians would have been used for reinforcing artillery after the beaches were secure.

 

The main concern for the ground forces was terrain and JA fortifications, not new JA armor, which was relatively unknown as Jason has pointed out.

 

Overall, the major challenges would have remained in the logistics of keeping the assault divisions in action while the USN and Commonwealth fleets fought off the hundreds of suicide aircraft, boats divers and minisubs. There would have been no shortages of equipment, aircraft and ships, but their overall coordination and deconfliction over truly vast distances would have made Normandy look simple.

[Inhapi]

Ordnance Dept was offering the T-29 heavy tank and the 240mm SP  then in prototypes 

 

 

Ken: was it realistic to get these trough army trails (MC trails) , then be modified with the feedback and then placed in production in time ?

[Ken Estes]

MG Barnes, the quixotic manager of Army Ordnance tank programs, had already ordered 1200 T-29 and 600 T-30, of which T-29/30 were reduced to 1152/504 on 12Apr45. I suspect that the rush to production would have required just what you mentioned. The first pilot T-29 was assembled prior to the end of the war but most priorities were slackened already upon the Japanese acceptance of terms so we cannot estimate how many production tanks could have been shipped to the Far East even if the acceptance trials went well.

[Nobu]

As many flamethrower tanks as could be deployed and brought to bear would be a priority as well, I would think. Losses among them would be heavy.

[Ken Estes]

Doctrinally, flame tanks were supported by at least two gun tanks. The main losses on Okinawa for all tanks were to the 47mm AT guns, first seen in significant numbers there and a hard lesson for Kyushu landings in the future.

[R011]

Japanese AT guns were more effective than is commonly thought, but surely no worse than German 5 cm and 7.5 cm guns - not to mention German Pzjg and StuG or 8.8 cm AT weapons. Did the Japanese have a Panzerfaust or Panzerschrek equivalent?

[Nobu]

Stripping away the accompanying infantry from such flamethrower and gun tank sections would be a priority as well, to expose them to the attention of Japanese tank-killing close assault teams attacking in relays.

 

Japanese AT guns were more effective than is commonly thought, but surely no worse than German 5 cm and 7.5 cm guns - not to mention German Pzjg and StuG or 8.8 cm AT weapons. Did the Japanese have a Panzerfaust or Panzerschrek equivalent?

 

A man-portable rocket launcher was produced, but not in numbers significant to the invasion of the Home Islands as far as I can recall.

Edited by Nobu, 17 November 2019 - 0043 AM.

[Rich]

MG Barnes, the quixotic manager of Army Ordnance tank programs, had already ordered 1200 T-29 and 600 T-30, of which T-29/30 were reduced to 1152/504 on 12Apr45. I suspect that the rush to production would have required just what you mentioned. The first pilot T-29 was assembled prior to the end of the war but most priorities were slackened already upon the Japanese acceptance of terms so we cannot estimate how many production tanks could have been shipped to the Far East even if the acceptance trials went well.

 

Barnes had no authority to order tanks, that was ASF and General Somervell.

 

On 1 March 1945, OCM 26825 recommended procurement of 1,200 Heavy Tanks T29, even though Pressed Steel Car Company had barely begun production of the first two pilots. Army Service Forces approved procurement of 1,152 on 12 April, along with four additional pilots, two of which were later ordered equipped with a 120mm Gun T53 and redesignated as the Heavy Tank T34. On 23 August, OCM 28848 cancelled the contract with Pressed Steel after it completed forging and welding a single pilot and partly finished the second. The order transferred all work to the Detroit Tank Arsenal and authorized just ten pilots for developmental studies, later reduced to eight by OCM 31654 of 10 July 1947. DTA finally delivered the first complete pilot to Aberdeen in October 1947 and two more in 1948.

 

The Supply Division, Army Service Forces, directed the limited procurement of 500 Heavy Tanks T30, sufficient to equip seven battalions, on 10 March 1945. The action was based on the recommendation of the New Developments Division of the Office of the Chief of Staff, which believed the T30 should be procured along with the T29, because the interchangeability of parts and use of the same production facility would simplify manufacture.  It appears these were included in the number ordered of the T29. As for the T29, the end of the war resulted in the cancellation of all except the pilots under OCM 28848 on 23 August 1945. T30 with a 155mm Gun T7, which was an adaptation of the standard 155mm Gun M1 used by the Field Artillery. One of the two pilots was later fitted with an experimental automatic ramming, cartridge case ejection, and elevation/depression system and was designated the T30E1. Both The two Heavy Tanks T30 did not arrive at Aberdeen until April and July 1948. Originally Ordnance intended them to use the Ford GAC engine, but like the T29E1 used them as testbeds for a new engine, the Continental AV-1790-3 as later used in the M26E2/M26A2. Although outwardly similar to the T29, Ordnance armed the pilots were fitted with a powered lifting device for handling the heavy and awkward separate loading ammunition.

[Rick]

 

MG Barnes, the quixotic manager of Army Ordnance tank programs, had already ordered 1200 T-29 and 600 T-30, of which T-29/30 were reduced to 1152/504 on 12Apr45. I suspect that the rush to production would have required just what you mentioned. The first pilot T-29 was assembled prior to the end of the war but most priorities were slackened already upon the Japanese acceptance of terms so we cannot estimate how many production tanks could have been shipped to the Far East even if the acceptance trials went well.

 

Barnes had no authority to order tanks, that was ASF and General Somervell.

 

On 1 March 1945, OCM 26825 recommended procurement of 1,200 Heavy Tanks T29, even though Pressed Steel Car Company had barely begun production of the first two pilots. Army Service Forces approved procurement of 1,152 on 12 April, along with four additional pilots, two of which were later ordered equipped with a 120mm Gun T53 and redesignated as the Heavy Tank T34. On 23 August, OCM 28848 cancelled the contract with Pressed Steel after it completed forging and welding a single pilot and partly finished the second. The order transferred all work to the Detroit Tank Arsenal and authorized just ten pilots for developmental studies, later reduced to eight by OCM 31654 of 10 July 1947. DTA finally delivered the first complete pilot to Aberdeen in October 1947 and two more in 1948.

 

The Supply Division, Army Service Forces, directed the limited procurement of 500 Heavy Tanks T30, sufficient to equip seven battalions, on 10 March 1945. The action was based on the recommendation of the New Developments Division of the Office of the Chief of Staff, which believed the T30 should be procured along with the T29, because the interchangeability of parts and use of the same production facility would simplify manufacture.  It appears these were included in the number ordered of the T29. As for the T29, the end of the war resulted in the cancellation of all except the pilots under OCM 28848 on 23 August 1945. T30 with a 155mm Gun T7, which was an adaptation of the standard 155mm Gun M1 used by the Field Artillery. One of the two pilots was later fitted with an experimental automatic ramming, cartridge case ejection, and elevation/depression system and was designated the T30E1. Both The two Heavy Tanks T30 did not arrive at Aberdeen until April and July 1948. Originally Ordnance intended them to use the Ford GAC engine, but like the T29E1 used them as testbeds for a new engine, the Continental AV-1790-3 as later used in the M26E2/M26A2. Although outwardly similar to the T29, Ordnance armed the pilots were fitted with a powered lifting device for handling the heavy and awkward separate loading ammunition.

 

Rich, an off topic question from an ex-sailor. Why did the Army use radial engines for tanks vs the Liberty engine?