What Can Japan Do To Improve The Performance Of Its WW2 Submarine Fleet?

Thank you for your reply. The reason nothing long term happened was because the IJA didn't want to provide the troops for an invasion when Ceylon was vulnerable, so the IJN settled for a raid and never came back. If the IJA provided 2 divisions, they would've taken the Island in April 1942. As for the Indian reaction not, much could happen for at least a year. They had no bases in southern India to stage an air siege of Ceylon, and there are no air forces to send there because their busy elsewhere trying to hold the line in Burma and Egypt. If they can't use the Bay of Bengal, they can't ship anything in.

As for building a sub, base on Ceylon the RN already had one and most of the port facilities would be captured before serious destruction would be possible. In real life blowing up a port is no easy task and needs a lot of time and preparation. In fact, there were several large ports on Ceylon that could be used for naval purposes. If the ATL decision is made to invade Ceylon and conduct major operation in the Indian Ocean the Midway Operation is at least on hold, but the Japanese could continue to advance in the Solomons. Nothing the Japanese could do in 1942 could hurt the Allies more than a long-term surge into the Indian Ocean.

In the event of the Japanese making such a move the British planned to move the bulk of their naval forces into the Indian Ocean. This would include all of their modern carriers, and most of their battleships. In a daytime carrier battle the RN would probably lose badly, so such an action would need to be avoided. They were fortunate that they didn't lose the modern carriers Formidable & Indomitable during the raid on Ceylon. Nagumo made a serious mistake in not putting out adequate search patrols. As it was his patrols came within 50 miles of finding Force A, and at one point both fleets were about 100 miles apart. A small strike force actually attacked the Japanese but scored no significant damage, and most of the aircraft were lost. Finding Force A would probably be its death sentence.

Once the Japanese have ships, subs, and aircraft on Ceylon the strategic danger for the Allies escalates dramatically. It would seriously change Allied global strategy for 1942 and effect major events for the rest of the war.


The ports & pens will be sabotaged when the invasion occurs

They don't need to ship planes in via the Bay of Bengal to hit Ceylon they can simply ship them to the west coast of India and fly them to the air bases in the south of India

I think the reason why the Japanese didn't do this is because they know they were never going to be able to hold an island less than 50miles off the coast of India, at least not without pinning the IJN to it and likely losing it! The IJA isn't going to drop 2 divisions on an island 50 miles off the coast and hope the IJN can keep them alive or get them off in time. The Japanese try this and the British & Co (and likely Americans) can bleed them dry all while having gin and tonics in their home base bars, and sleeping in proper beds, while the IJN tries to operate (even further) from it's big bases.

The IJN raids into the Indian ocean benefited with strategic surprise (generally) but if they try this they will lose that advantage. The big reason why teh IJN is hang around was because they know they were operating at the outer edge of their effective range, and teh the water were only going to get more dangerous for them

And don't forget while all this is happen the USN is revving up, you have the postpone midway for this? You have them not going through with their decisive battle in order to pin the IJN to an island 50 miles off the cost of India)

You are right Ceylon OTL wasn't a big priority but if this happens it will become so because Ceylon is important and because it will be a great opportunity to actually attack the IJN for as long as it's dumb enough to stick around

Why do you think there weren't any air fields in the south of India?

Also you mention Burma but that works both ways teh Japanese are also still fighting in Burma at this point!
 
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The Indian Ocean was the vulnerable area in 1942. What the Germans call the Zeitpunkt should have been pushed harder on. The German Type IX Boats were doing very well but would've done better with an operational base in the region. Adding a half a dozen Japanese subs and the pressure on the Allies becomes much greater. In 1942 the Allies are sending vital convoys to Egypt, (To stop Rommel) Iran, (For Russia) and Assam, (Which effects China).
Just because it was vulnerable doesn't automatically equate to another dozen Japanese subs having this massive effect.

and

Just because it was vulnerable OTL with OTL axis activity doesn't it mean it will stay as vulnerable in an ATL.
 
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The ports & pens will be sabotaged when the invasion occurs

They don't need to ship planes in via the Bay of Bengal to hit Ceylon they can simply ship them to the west coast of India and fly them to the air bases in the south of India

I think the reason why the Japanese didn't do this is because they know they were never going to be able to hold an island less than 50miles off the coast of India, at least not without pinning the IJN to it and likely losing it! teh IJA isn't going to drop 2 divisions on an island 50 mile off the coast and hope the IJN can keep them alive or get them off in time. The Japanese try this and the British & Co (and likely Americans) can bleed them dry all while having gin and tonics in their home base bars, and sleeping in proper beds, while the IJN tries to operate (even further) from it's big bases

The IJN raids into teh Indian ocean can with strategic surprise (generally) but if they try this they will lose that advantage.

You are right Ceylon OTL wasn't big priority but if this happens it will become so because Ceylon is important and because it will be a great opportunity to actually attack the IJN for as long as it's dumb enough to stick around

Why do you think there weren't any air fields in the south of India?

Also you mention Burma but that works both ways teh Japanese are also still fighting in Burma at this point!
So, what was the strength of the RAF in Southern India in 1942? Almost nothing because naval, air, and ground forces were being sent to Ceylon. A Japanese invasion of Ceylon in April 1942 would destroy most of those forces. In May/June 1942 Rommel destroyed 1/2 of 8th Army at the Battle of Gazala, and then raced into Egypt. At that point Egypt was the crisis point and was till November 1942. There are no large-scale forces anywhere in the world to send to India except the redeployment of the RN in a risky deployment into the Indian Ocean.
 
The Indian Ocean was the vulnerable area in 1942. What the Germans call the Zeitpunkt should have been pushed harder on. The German Type IX Boats were doing very well but would've done better with an operational base in the region.

U-boats had access to Japanese bases in Penang, Surabaya and Singapore, but IIRC not until 1943.

Adding a half a dozen Japanese subs and the pressure on the Allies becomes much greater. In 1942 the Allies are sending vital convoys to Egypt, (To stop Rommel) Iran, (For Russia) and Assam, (Which effects China).
Considering the extreme hazards of operating in the Atlantic, especially for the slower-diving type IXs, it probably would've been a good idea to transfer the bulk of IXs to bases in the Far East, though logistics was a problem.
 
So, what was the strength of the RAF in Southern India in 1942? Almost nothing because naval, air, and ground forces were being sent to Ceylon. A Japanese invasion of Ceylon in April 1942 would destroy most of those forces.
I think this is another argument for Invasion India. "Hit 'em where they ain't." Ceylon can be isolated the same way the Allies isolated Rabaul and turned into one big POW camp.
 
I think this is another argument for Invasion India. "Hit 'em where they ain't." Ceylon can be isolated the same way the Allies isolated Rabaul and turned into one big POW camp.
Respectfully how do the Japanese invade India in 1942? By the rainy season they had to stop, and their supply lines from Rangoon were too long. Only a long-term presence of the IJN in the Bay of Bengal would give the Japanese the ability to use sea supply lines and deign that to the Allies. Rabaul was isolated in 1944 because the Allies had amphibious forces to take island bases behind it. Where are the Allies going to land behind Ceylon? In 1943 the Allies weren't able to provide sea lift for even 1 division in the Indian Ocean because of their global commitments. Even if they had shipping for one division where would they base from and would they sail into waters controlled by enemy air power, and where they have no air support?
 
So, what was the strength of the RAF in Southern India in 1942? Almost nothing because naval, air, and ground forces were being sent to Ceylon.


Seriously Ceylon is less than 50 miles off the coats of southern India you post like there are remote from each other

You seem to assume that the Japanese just have to turn up and the forces in Ceylon will not only be wiped out but that they are the only UK & Co forces in all of Southern Asia & East Africa that can respond.

A Japanese invasion of Ceylon in April 1942 would destroy most of those forces.

A Japanese invasion has to be entirely brought in long distance by sea all while they are still fighting in Burma etc and consolidating the rest of the winnings and dealing with the Pacific / USN

You also seme to assume that it's just matter of the Japanese coming over the horizon and Ceylon falls forever this is unrealistic

I think you are looking at the earlier Japanese victories and assuming that's just how it goes as a base line of expectation, this is unrealistic

In May/June 1942 Rommel destroyed 1/2 of 8th Army at the Battle of Gazala, and then raced into Egypt. At that point Egypt was the crisis point and was till November 1942. There are no large-scale forces anywhere in the world to send to India except the redeployment of the RN in a risky deployment into the Indian Ocean.
They don't need large scale forces because Japan doesn't have large amounts of resources to put in this themselves. This is why they only did raids and subs from bases on the east coast of the Indian ocean

Egypt was ongoing but it doesn't drag in everything the UK & Co had

RN deployment in the Indian ocean becomes a lot less risky if the IJN in the Indian ocean is stuck supporting an invasion of Ceylon

Yes the UK & Co are gong to have to move some stuff around to meet this new issue but they will do so


I think the issues are;

1). you don't recognise how Ceylon's proximity to India makes this plan a bad one, not just for the invasion but any attempt to keep it

2). you don't realise how different raiding and invading are from each other, especially for the IJN here in the Indian Ocean

3). you are giving the Japanese the benefits of our hindsight, they don't know what the forces on Ceylon and south India are, they do however know their own forces and how far out they are operating

Anyway I found this it gives a pretty good summary of the wider context, the raids and invasion plans the movement of UK & Co troops OTL and the reality of the Japanese situation. Don't worry it also goes into the less than stellar UK performance as well, and make's your Egypt point as well!

I've highlighted two sections in bold that goes straight to the heart of all this


During the Second World War, Ceylon was an important location for the British to impose their control over the Indian Ocean, and the trading routes to India, South Africa, and Europe. A major Royal Navy base was established on the east coast at Trincomalee, and Colombo was the other important port on the island. A locally raised Militia was raised in 1881, which by 1910, had become the Ceylon Defence Force. There were no British troops stationed on the island, until the Second World War.

The Japanese attack on Malaya, the Philippines (under U.S. administration), and the Netherland East Indies on 7 December 1941, changed the balance of power in the region drastically. As the build-up to conflict occurred, Ceylon was taken under India Command with effect from 22 November 1941. With the rapid advance of the Japanese forces across South-East Asia, the threat of invasion of Ceylon, in particular, the east coast around Trincomalee, meant that British forces on the island had to be strengthened significantly. With the loss of Malaya, Ceylon became the main source of rubber for the British Empire. Vice Admiral Geoffrey LAYTON was appointed the Commander-in-Chief, Ceylon, in March 1942, and he began to reorganise the defences to face a probable attack.

The first eight Hawker Hurricane fighters arrived on 23 February 1942, having been assembled in Karachi, and flown down to Ceylon. These formed No. 258 Squadron, which in April, was based at the newly opened airfield at Colombo Racecourse. Another sixty arrived on 6 and 7 March, having been flown off H.M.S. Indomitable, to form No. 30 and No. 261 Squadrons. The former was based at R.A.F. Ratmalana, and the latter at R.A.F. China Bay at Trincomalee. The Bristol Blenheims of No. 11 Squadron were also based at Colombo Racecourse. The Fleet Air Arm provided No. 803 and No. 806 Naval Air Squadrons, equipped with forty-four Fairey Fulmers.

Two Australian infantry brigades, the 16th and 17th, were diverted from their journey back to Australia from the Middle East, to provide an initial garrison for the island, pending the arrival of other troops. The 34th Indian Infantry Division had been raised at Jhansi in October 1941, and it was still not fully trained or equipped, but it was ordered to Ceylon in January 1942. It was stationed in and around Trincomalee, being responsible for coastal and airfield defence. Ceylon Army Command was formed with effect from 7 March 1942, based at Colombo, with Lieutenant General Sir Henry POWNALL, K.B.E., C.B., D.S.O., M.C., p.s.c., as the first General Officer Commanding-in-Chief. Anti-Aircraft defences were built up rapidly, with the 1st Royal Marine Anti-Aircraft Brigade being responsible for the defence of Trincomalee, and the 23rd Anti-Aircraft Brigade responsible for Colombo and its environs, including the R.A.F. base at Ratmalana.

Commencing on 31 March 1942, the Imperial Japanese Navy launched a major operation against the British Eastern Fleet, based at Trincomalee. Singapore had fallen on 15 February 1942, and two Royal Navy warships, H.M.S. Prince of Wales and H.M.S. Repulse had been sunk off the eastern coast of Malay by Japanese aircraft, making Ceylon and Southern India vulnerable to Japanese aggression.

The Japanese occupied the Andaman Islands on 23 March 1942, adding to the concerns about an invasion of Ceylon. Fortunately for the British, the Imperial Japanese Army was unable to commit any troops to an invasion of Ceylon, so it fell to the Navy to carry out an offensive against the British in the Indian Ocean. Admiral Isoroku YAMAMOTO commanded what was known as Operation ‘C’, which commenced on 26 March 1942. The intention was to attack the British Eastern Fleet in port at Colombo on 5 April, and the Japanese were confident of being able to do so. The Japanese naval force comprised five aircraft carriers and four battleships, vastly out-numbering the small Royal Navy presence in the area. Vice-Admiral Sir James SOMERVILLE commanded three aircraft carriers, the modern H.M.S. Formidable and H.M.S. Indomitable, and the older H.M.S. Hermes. H.M.S. Warspite acted as the flagship of the Fleet, which also comprised four Revenge class battleships. SOMERVILLE’s intention was to avoid direct contact, and to preserve his fleet in being.

By 4 April 1942, the R.A.F. and F.A.A. strength on Ceylon was sixty-seven Hawker Hurricanes, and forty-four Fairey Fulmer fighters. There were also seven long-range Catalinas for reconnaissance, fourteen Bristol Blenheims, and twelve Fairey Swordfish torpedo bombers. The R.A.F. elements were part of No. 222 Group, commanded by Air Vice Marshal John D’ALBIAC.

Allied intelligence knew of the Japanese force heading towards Ceylon, but in underestimated the strength of it. At about 16.00 hours on 4 April, a Catalina from No. 413 Squadron, R.C.A.F., sighted the Japanese fleet south-east of Ceylon. A second Catalina, R/205 from No. 205 Squadron, R.A.F., was shot down on 5 April while shadowing the Japanese naval forces. Vice Admiral LAYTON ordered the ships in the harbours at Colombo and Trincomalee to put to sea, to avoid being attacked in harbour. This included the cruisers H.M.S. Cornwall and H.M.S. Dorsetshire which sailed from Colombo, and the small aircraft carrier, H.M.S. Hermes, which sailed from Trincomalee with orders to hide north-east of Ceylon.

On 5 April 1942, the Japanese launched an air strike on Colombo, and as they passed over the main R.A.F. base at Ratmalana, just south of Colombo, the British fighters were still on the ground. The Japanese attacked the remaining ships in the harbour, sinking the armed merchant cruiser, H.M.S. Hector, the destroyer H.M.S. Tenedos, and a Norwegian tanker. An air battle took place over Colombo, with the British losing twenty of the forty-one aircraft that had taken off, plus six Swordfish from No. 788 Squadron, F.A.A., which were airborne armed with torpedoes. The Japanese lost about seven aircraft.

At about 10.00 hours, a Japanese aircraft found H.M.S. Dorsetshire and H.M.S. Cornwall, and it began shadowing the two Royal Navy cruisers. The Japanese aircraft carriers rearmed their planes with torpedoes, and they started taking off at 11.45 hours. They homed in onto the two Royal Navy cruisers, which were attacked and sunk at about 14.00 hours. Four-hundred and twenty-four officers and men were lost from the two warships.

The British fleet were searching for the Japanese warships, and some elements were spotted by two Albacores, with one being shot down. The main body of the Japanese fleet was not sighted, as it had turned away from Ceylon to the south-west. The two fleets missed each other for various reasons, but on 6 April, two Japanese heavy cruisers sank five merchant ships. The Eastern Fleet then withdrew to refuel, now being aware of the size of the Japanese force in the Indian Ocean.

On 8 April, the Japanese fleet approached Trincomalee from the east, and they were detected by a Catalina aircraft at 15.17 hours. The harbour was cleared, with H.M.S. Hermes and H.M.A.S. Vampire beings sent to the south along the coast. This time, the Japanese strike group of one-hundred and thirty-two aircraft was detected prior to the attack. The defending fighters, seventeen Hurricanes and six Fulmers were airborne to meet the raid.

The Japanese attacked the harbour and the China Bay airbase, causing significant damage. The civilian population were badly alarmed, with many fleeing from the town. A merchant ship was hit and caught fire, and the monitor, H.M.S. Erebus was damaged. Eight Hurricanes and one Fulmer were shot down, for the loss of four Japanese aircraft. A Catalina from No. 413 Squadron, R.C.A.F., was also shot down while shadowing the Japanese fleet.

At about 10.25 hours, nine unescorted Bristol Blenheim aircraft from No. 11 Squadron located and attacked the Japanese carrier force. They dropped their bombs from 11,000 feet, and although some bombs fell close to one of the carriers, none were hit. Four Blenheims were shot down during the attack, with one later being shot down from aircraft returning from attacking H.M.S. Hermes. Although leaving Trincomalee, H.M.S. Hermes and her escort, H.M.A.S. Vampire, were located shortly after the attack on Trincomalee, and they were attacked by about eighty Japanese bombers, near Batticaloa. Both warships were overwhelmed, with H.M.S. Hermes being hit by about forty 500 lb bombs. Three-hundred and seven men from H.M.S. Hermes, and eight from H.M.A.S. Vampire were lost. Other ships nearby were attacked, including the corvette, H.M.S. Hollyhock, a naval auxiliary, a tanker, and a cargo ship.

The Japanese fleet withdrew after attacking Trincomalee, but the events had highlighted the British position of weakness in defending Ceylon and southern India. The Eastern Fleet withdrew its base to Kilindini in Kenya, ceding control of the eastern Indian Ocean to the Japanese. The British intelligence indicated that the Japanese were intending an invasion of Ceylon, so the defences were improved and strengthened. Three additional R.A.F. Squadrons arrived on Ceylon, including No. 222 Squadron equipped with Bristol Beaufort maritime strike aircraft.

The first Army formations sent to the island were the two Australian brigades, as detailed above, which were followed by the 34th Indian Infantry Division. The arrival of the Indian division allowed the two Australian brigades to continue their journey to Australia by late April.

In June 1942, the Imperial Japanese Army developed plans for a major offensive in the Indian Ocean, including an invasion of Ceylon. As the German and Italian forces were advancing in North Africa, thoughts were given to linking up Axis forces in the Middle East. The Imperial Japanese Navy was, even by this early date in the war, over-committed, with the main threat coming from the U.S. forces in the Pacific region. The Japanese limited themselves to submarines patrolling the Indian Ocean to attack shipping, but after the events of April 1942, no more major Japanese naval units were deployed to the Indian Ocean.

The build-up of Army forces on Ceylon continued through 1942. The 21st (East Africa) Infantry Brigade arrived on the island on 21 March 1942. The 20th Indian Infantry Division arrived in mid-1942, and in June 1943, with the threat reduced, the 34th Indian Infantry Division was disbanded, and the 20th Indian Infantry Division departed for North-West India and Burma. The other two Brigades of the 11th (East Africa) Infantry Division arrived in June 1943, consolidating the division on Ceylon, where it became the main garrison force. In respect of the anti-aircraft defences, the 1st Royal Marine Anti-Aircraft Brigade departed, and so the 24th Anti-Aircraft Brigade was formed to cover Trincomalee. In May 1944, the 11th (East Africa) Infantry Division departed for deployment in Burma, and the 23rd Anti-Aircraft Brigade also saw service in Burma. The 24th Anti-Aircraft Brigade remained on Ceylon until it was disbanded.
 
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3). you giving the Japanese the benefits of our hindsight, they doesn't what the forces on Ceylon and south India are, they do however know their own forces and how far out they are operating
My understanding is that the Japanese overestimated the strength of British forces in India during 1942, and underestimated what was present on Ceylon at the time.
 
My understanding is that the Japanese overestimated the strength of British forces in India during 1942, and underestimated what was present on Ceylon at the time.
I don't really know which way round it was, but the point was they can't use wiki like we can to know the garrison strengths of various bases.

However two points are raised by what you say:

1). if they underestimated the UK & Co forces on Ceylon and still don't go for it that tells us something

2). they probably recognised that Indian and Ceylon are not that remote from each other.
 
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1). if they underestimated the UK & Co forces on Ceylon and still don't go for it that tells us something
Refusing to go for Ceylon despite the underestimate was hardly a unanimous decision. Major figures in the IJN were positively jonesing for it but it was the who IJA scuppered the plan by refusing to contribute the manpower for an invasion force, much to the IJN's frustration.

The thoughts of Yoshitake Miwa, Combined Fleet Air Staff Air Officer, were typical: "We want to invade Ceylon; we are not allowed to! We want to invade Australia; we cannot! We want to attack Hawaii; we cannot do that either! All because the damned army will not agree to release the necessary forces. Though it is understandable that the army has to retain troops to deal with the Soviet Union, is it THAT impossible to spare us just one or two divisions out of a million men in Manchuria and 400,000 in China?"
 
Refusing to go for Ceylon despite the underestimate was hardly a unanimous decision. Major figures in the IJN were positively jonesing for it but it was the who IJA scuppered the plan by refusing to contribute the manpower for an invasion force, much to the IJN's frustration.

The thoughts of Yoshitake Miwa, Combined Fleet Air Staff Air Officer, were typical: "We want to invade Ceylon; we are not allowed to! We want to invade Australia; we cannot! We want to attack Hawaii; we cannot do that either! All because the damned army will not agree to release the necessary forces. Though it is understandable that the army has to retain troops to deal with the Soviet Union, is it THAT impossible to spare us just one or two divisions out of a million men in Manchuria and 400,000 in China?"
well ok a few points

1). it makes the point that you can't invade with just the IJN you need the IJA (literally) on board with the idea

2). The IJA was tied up in a lot of different places at this point weather or not the IJN thinks so or not. They're still fighting in Burma they've only just taken everywhere else. They are building their perimeter of bases in teh pacific to ward of the US that have to be manned.

2a). the IJA know that if the invasion of Ceylon goes badly their pals in the IJN can sail off (or be sunk), any IJA forces left on Ceylon when that happens are lost

2b). It not just any two Dvis they need, these boys ard going to do an amphibious assault and then take and hold a large island 50 miles of thd coast of India. They need to be good Divs, not only do you need good Divs but given the last 6 months this good Divs they have are probably being used or having just done a whole bunch of fighting and need Rest & Refit

2c). Do you think the IJA trust the IJNs appraisal for what ground forces are needed to subdue Ceylon, anymore than the IJN would trust the IJA's appraisal of how many battleships the IJN would need at Midway?

3). I trust the IJA to now what spare divisions it has more than I trust teh IJN to know

4).. almost no decision is unanimous ever, that in itself doesn't necessarily represent anything more than the basic fact there was some disagreement
 
The Irony is as per the link in my post

early in 1942 the IJN are ready to go but the IJA have their hands too full, and later when the IJA are more keen* now the IJN are the ones looking over their shoulders and thinking no maybe not.

what can I say, no one ever said conquering the world was easy!


*although as part of a much wider more ambitious invasion of the whole area that's functionally a pincer attack on India! (to be fair I don't think this larger plan got very far in 1942 IJN or not)
 
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Refusing to go for Ceylon despite the underestimate was hardly a unanimous decision. Major figures in the IJN were positively jonesing for it but it was the who IJA scuppered the plan by refusing to contribute the manpower for an invasion force, much to the IJN's frustration.

The thoughts of Yoshitake Miwa, Combined Fleet Air Staff Air Officer, were typical: "We want to invade Ceylon; we are not allowed to! We want to invade Australia; we cannot! We want to attack Hawaii; we cannot do that either! All because the damned army will not agree to release the necessary forces. Though it is understandable that the army has to retain troops to deal with the Soviet Union, is it THAT impossible to spare us just one or two divisions out of a million men in Manchuria and 400,000 in China?"
Keep in mind, if they do invade they need to keep the combined carrier fleet off shore for weeks to support against any defenses and keep the area supplied to conduct a sustained naval campaign. Singapore was just captured Feb 15 42-its not possible to bypass it logistically so March was the earliest time, Ceylon was reinforced with troops from North Africa in early 42 - the British IOTL also had advance warning of Operation C so I don't know where the idea of an unopposed invasion comes from. The two-three divisions needed and naval strength also need to be supplied at a 3000km distance further from Tokyo than Hawaii across the unsecured Indian Ocean-a tempting target for Allied submarines.

They had already combed the better divisions from China for the Centrifugal offensive. Where are they going to get the shipping capacity for the invasion fleet? You can't do it until June 42 due to the shoe-string budget of the Centrifugal Offensive-take a division/shipping from one place and you won't have something vital like Sumatra taken, Japan started the war 30% short of shipping capacity needed for domestic industry-it was further forced down to stockpiles and self-blockade by the devotion of the 80% of the merchant fleet to the Centrifugal Offensive leaving Japanese industry and civilians with an unsustainable 14% of its needed shipping tonnage in the first half of 42.

The Southern Sri Lankan monsoon constrains operations and air support to after June for Colombo. The only other major port and airfield is Trincomalee on the Eastern coast has the deadline of December as the start of the weaker Bengali monsoon. But if we delay Operation C to include an invasion force then we're looking at the Midway disaster happening in June and Guadalcanal in August leaving the IJN needing carrier capacity in the Pacific and wary of extending further.

I question how a dozen or so subs can be steadily supplied in Ceylon, how are they going to find targets stretched across another whole ocean? They barely had an effect on merchant traffic in the Pacific but they gain a buff while also spread out across the Indian Ocean why? How do they protect a supply line further from Tokyo than Hawaii with hostile Indian territory right beside the destination?

Sometimes this thread's casual dismissal of logistics and enemy strength feels like I'm in a historical imperial conference talking to IJA and IJN chiefs landing poorly supplied brigades on Guadalcanal against a full Marine division with air support.
 
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Keep in mind, if they do invade they need to keep the combined carrier fleet off shore for weeks to support against any defenses and keep the area supplied to conduct a sustained naval campaign. Singapore was just captured Feb 15 42-its not possible to bypass it logistically so March was the earliest time, Ceylon was reinforced with troops from North Africa in early 42 - the British IOTL also had advance warning of Operation C so I don't know where the idea of an unopposed invasion comes from. The two-three divisions needed and naval strength also need to be supplied at a 3000km distance further from Tokyo than Hawaii across the unsecured Indian Ocean-a tempting target for Allied submarines.
No, you don't need the combined carrier fleet offshore for weeks. What the fleet has to do is knockout the land-based aircraft on the Ceylon and defeat the Eastern Fleet. That would take about a week. Operation C destroyed about half the Allied Aircraft on Ceylon in 2 raids. The IJA would start flying in aircraft as soon as they could capture a landing strip. The Eastern Fleet underestimated the size of the carrier force and nearly destroyed themselves by getting too close to the Japanese. A fleet with an invasion force behind it would've searched more diligently for a hostile naval force. The Allies only had 7 submarines in the Indian Ocean and none of them did any damage to the IJN during the OTL battle.

The problem with protecting an island 250 miles long, and 100 miles wide is you can't defend the whole thing. The 34th Indian Division and the 16th & 17th Australian Brigades had most of their forces defending the 2 chief ports, and the Japanese wouldn't oblige them by making a frontal assault on a defended port. There are numerous smaller ports with accessible beaches on Ceylon where the Japanese can land and move overland to their objectives. In similar terrain in Malaya, and in the jungle fighting in Burma the Japanese completely outfought the Commonwealth Army despite being outnumbered. On Ceylon the Japanese would have air superiority and equal or greater overall numbers. The Australian and British brigades on the island just came from the desert and have no training in jungle warfare.
They had already combed the better divisions from China for the Centrifugal offensive. Where are they going to get the shipping capacity for the invasion fleet? You can't do it until June 42 due to the shoe-string budget of the Centrifugal Offensive-take a division/shipping from one place and you won't have something vital like Sumatra taken, Japan started the war 30% short of shipping capacity needed for domestic industry-it was further forced down to stockpiles and self-blockade by the devotion of the 80% of the merchant fleet to the Centrifugal Offensive leaving Japanese industry and civilians with an unsustainable 14% of its needed shipping tonnage in the first half of 42.
After the fall of Singapore and Sumatra the Japanese Southern Army shipped the 2nd Imperial Guard Division, along with the 4th & 5th Divisions back Japan, and the 16th too Manchuria. There were plenty of troops for Ceylon, and the IJN thought they did have the amphibious shipping for the operation, or they never would've suggested it. Japan spent the whole war with a merchant shipping deficit but were able to conduct major offensive operations.
The Southern Sri Lankan monsoon constrains operations and air support to after June for Colombo. The only other major port and airfield is Trincomalee on the Eastern coast has the deadline of December as the start of the weaker Bengali monsoon. But if we delay Operation C to include an invasion force then we're looking at the Midway disaster happening in June and Guadalcanal in August leaving the IJN needing carrier capacity in the Pacific and wary of extending further.
Operation C had no trouble with the weather. The weather was fine in April, and Allied Intelligence thought the Japanese would invade the Island in April. No Coral Sea or Midway would be great for the Japanese. They don't even need the carrier fleet to move into the Solomons. Midway is what made Guadalcanal possible. With the IJN carrier, and battleship superiority the Americans would never risk their carrier fleet, and a Marine Corps division in an offensive operation.
I question how a dozen or so subs can be steadily supplied in Ceylon, how are they going to find targets stretched across another whole ocean? They barely had an effect on merchant traffic in the Pacific but they gain a buff while also spread out across the Indian Ocean why? How do they protect a supply line further from Tokyo than Hawaii with hostile Indian territory right beside the destination?

Sometimes this thread's casual dismissal of logistics and enemy strength feels like I'm in a historical imperial conference talking to IJA and IJN chiefs landing poorly supplied brigades on Guadalcanal against a full Marine division with air support.
A dozen Axis subs in an area with almost no ASW forces, and where vital convoys have to pass though can-do massive damage. Look what a half dozen U-Boats were able to do off the U.S. East Coast in early 1942. With the loss of Ceylon, the Bay of Bengal would be closed, and Allied subs would have to base out of Bombay, so how far do they have to go to threaten the supply line to Ceylon?

In 1942 Allied logistics are being strained. The Japanese were starving on Guadalcanal because the Allies had air superiority, the jungle leading to the marine perimeter was nearly trackless, and the Japanese never realized they were heavily outnumbered on land. At Ceylon the Japanese would have air superiority, naval dominance, outnumber the enemy on land, have control of ports and have roads to move supplies down with native labor to support operations. The Japanese have most of the advantages in a Ceylon invasion, the Allies were on the backfoot scrambling to get ready for an attack.
 
No, you don't need the combined carrier fleet offshore for weeks. What the fleet has to do is knockout the land-based aircraft on the Ceylon and defeat the Eastern Fleet. That would take about a week.
This sounds exactly like an IJN plan, ridiculously optimistic. The naval performance here is not only flawless, it does multiple tasks at the same time by supporting an invasion while fighting the Eastern Fleet at the same time. Because the IJN had a stellar record of naval recon while doing an invasion while trying to force a naval battle like Midway. All within a week too, faster than Malaysia, Java or Brunei all of which were close to Japanese bases with careful prewar HUMIT, preparations, and stockpiles. None of that here in Ceylon but you're gonna just ignore that.
Operation C destroyed about half the Allied Aircraft on Ceylon in 2 raids. The IJA would start flying in aircraft as soon as they could capture a landing strip. The Eastern Fleet underestimated the size of the carrier force and nearly destroyed themselves by getting too close to the Japanese. A fleet with an invasion force behind it would've searched more diligently for a hostile naval force.
Just like Midway right? Given your time table of a week, they'd have to do everything at the same time: support the invasion, recon, CAP, and be ready for a mass carrier strike all on 5 decks. All at a distance 3000 km further than Pearl Harbor while also supplying two divisions for heavy fighting. Where are the oilers and supply ships coming from?

The Allies only had 7 submarines in the Indian Ocean and none of them did any damage to the IJN during the OTL battle.
And that applies to a supply line how? Did Japan build supply ships with aircraft groups, cruisers, and the ability to cruise at combat speeds?

That number won't stay low once the Japanese try to supply a permanent force. It's a poorly thought out POD where the Allies don't react at all while the Japanese make different choices.
The problem with protecting an island 250 miles long, and 100 miles wide is you can't defend the whole thing. The 34th Indian Division and the 16th & 17th Australian Brigades had most of their forces defending the 2 chief ports, and the Japanese wouldn't oblige them by making a frontal assault on a defended port.
But yet you assume the Eastern Fleet will just sail to their doom within a week, that Summerville won't change anything despite his decent strategic Intel historically. Name one opposed invasion 2600 km from the nearest major friendly port that the Japanese succeeded in historically.

There are numerous smaller ports with accessible beaches on Ceylon where the Japanese can land and move overland to their objectives. In similar terrain in Malaya, and in the jungle fighting in Burma the Japanese completely outfought the Commonwealth Army despite being outnumbered. On Ceylon the Japanese would have air superiority and equal or greater overall numbers.
Air cover for a week, your words. At a distance further from Truk or Saigon who are somehow supplied better than the starving Japanese soldiers in New Guinea, Solomons, or U-Go later, and right by British bases. Still sounds like an IJA plan with total disregard for logistics.

The Australian and British brigades on the island just came from the desert and have no training in jungle warfare.
Contradicted by the historical record of the Aussies as some of the best infantry in the Pacific, even the green troops in New Guinea.
After the fall of Singapore and Sumatra the Japanese Southern Army shipped the 2nd Imperial Guard Division, along with the 4th & 5th Divisions back Japan, and the 16th too Manchuria.
Except unlike shipping them back to Japan this is the opposite direction away from the source of supplies, logistics is how the Pacific war was fought.
There were plenty of troops for Ceylon, and the IJN thought they did have the amphibious shipping for the operation, or they never would've suggested it.
That's not a justification, they also thought they can invade Alaska through the Aleutians, actually tried it, and that Americans were cowards who'd sue for peace. Heck they gambled their nation on a racist delusion.

Japan spent the whole war with a merchant shipping deficit but were able to conduct major offensive operations.
As long as we account for starving troops and failed offensives then it's all true. They did conduct offensive operations with logistical deficits, as soon as the distance became further than a few hundred kilometers beyond their 1941 positions they stalled everywhere with starving soliders by the thousands.
Operation C had no trouble with the weather. The weather was fine in April, and Allied Intelligence thought the Japanese would invade the Island in April. no Coral Sea or Midway would be great for the Japanese. They don't even need the carrier fleet to move into the Solomons. Midway is what made Guadalcanal possible. With the IJN carrier, and battleship superiority the Americans would never risk their carrier fleet, and a Marine Corps division in an offensive operation.
And with no midway the IJN would instead do something else stupid to force a "decisive battle" while ignoring the lack of anything important to the Americans within reach or their own shoddy codes. Or they would've gone with Operation FS that was historically cancelled by Midway and overreacted at a more precarious position. Anything to 'shock the Americans to surrender ' before America mobilized and crushed them.
A dozen Axis subs in an area with almost no ASW forces, and where vital convoys have to pass though can-do massive damage. Look what a half dozen U-Boats were able to do off the U.S. East Coast in early 1942.
Yeah, they sank half a percentage point of American shipping capacity while Americans just replaced them. The East coast was planned and done by German captains trained in commerce raiding against a naive America, in contrast you have IJN subs trained for the decisive battle with a much smaller fleet. Given the general rule of 1/3s for naval readiness you'd need nearly half the IJN sub fleet to maintain a dozen subs in the Indian Ocean.

With the loss of Ceylon, the Bay of Bengal would be closed,
With what exactly? Japan's renowned deficiency in ASW? The air fleet that only stayed for a week? The supply chain of tankers bringing AVgas to Ceylon?
and Allied subs would have to base out of Bombay, so how far do they have to go to threaten the supply line to Ceylon?

In 1942 Allied logistics are being strained. The Japanese were starving on Guadalcanal because the Allies had air superiority, the jungle leading to the marine perimeter was nearly trackless, and the Japanese never realized they were heavily outnumbered on land. At Ceylon the Japanese would have air superiority, naval dominance, outnumber the enemy on land,
Because the Japanese were known for realistic intel assessments after the Centrifugal Offensive. It's 2000 km from Burma to Ceylon beyond the range of a lot of Japanese aircraft, are the Japanese going to keep escort carriers in the bay of Bengal to ferry the planes there? Or are they going to scout and dominate an ocean with only bombers that can fly there?

have control of ports and have roads to move supplies down with native labor to support operations.
Ah yeah, the empire that managed to create uprisings and resistance movements in every land it conquered is going to get the help of the natives for any substantial period of time. They probably will initially til they realize how much crueler the Imperial Japanese were.
 
Contradicted by the historical record of the Aussies as some of the best infantry in the Pacific, even the green troops in New Guinea.
Australian troops were the only Allied soldiers the Japanese openly admitted they admired in terms of skill. Yup, they didn't even afford the Americans that sort of begrudging respect.

Ah yeah, the empire that managed to create uprisings and resistance movements in every land it conquered is going to get the help of the natives for any substantial period of time. They probably will initially til they realize how much crueler the Imperial Japanese were.
I often like to say that the general population of India was so pro Japan and anti British because they never had the misfortune of actually being occupied by the Japanese.
 
I often like to say that the general population of India was so pro Japan and anti British because they never had the misfortune of actually being occupied by the Japanese.
Part of the issue was the lack of Japanese shipping and industry: they didn't have the consumer goods to trade with the locals for anything even if they wanted to, which they didn't anyways.

The British, Dutch, and French could all give the locals manufactured goods in return in contrast to Japanese bayonets.
 
This sounds exactly like an IJN plan, ridiculously optimistic. The naval performance here is not only flawless, it does multiple tasks at the same time by supporting an invasion while fighting the Eastern Fleet at the same time. Because the IJN had a stellar record of naval recon while doing an invasion while trying to force a naval battle like Midway. All within a week too, faster than Malaysia, Java or Brunei all of which were close to Japanese bases with careful prewar HUMIT, preparations, and stockpiles. None of that here in Ceylon but you're gonna just ignore that.
What is so ridiculously optimistic about destroying the Eastern Fleet in a week? In the OTL Summerville enjoyed amazing luck that Nagumo failed to put out what should've been an SOP recon search pattern. Just doing what they did at Midway would've found Force A in the late morning of April 5th. The first day of fighting would've likely ended with Indomitable & Formidable at the bottom of the sea along with the 2 CA's. On April 6th a second attack would've gone after Summerville's battleships, now with no air cover. The raid on the 9th would like in the OTL sink the Hermes.
Just like Midway right? Given your time table of a week, they'd have to do everything at the same time: support the invasion, recon, CAP, and be ready for a mass carrier strike all on 5 decks. All at a distance 3000 km further than Pearl Harbor while also supplying two divisions for heavy fighting. Where are the oilers and supply ships coming from?
That's a bit of a jumble. After the 9th in the OTL most of the strike aircraft on Ceylon were destroyed and if the IJN finds them Force A is destroyed too so the airfields can be attacked again at leisure and a landing follow right after. Yes, if the Japanese decide to invade, they will factor in supplies. The IJA will fly in aircraft from the Andaman Islands, and the IJN will send some of their land-based aircraft because they want to do something as irrational as win. With air superiority over Ceylon, it's not so easy for the Allies to sail ships east of the Island to attack supply ships.
And that applies to a supply line how? Did Japan build supply ships with aircraft groups, cruisers, and the ability to cruise at combat speeds?

That number won't stay low once the Japanese try to supply a permanent force. It's a poorly thought out POD where the Allies don't react at all while the Japanese make different choices.

But yet you assume the Eastern Fleet will just sail to their doom within a week, that Summerville won't change anything despite his decent strategic Intel historically. Name one opposed invasion 2600 km from the nearest major friendly port that the Japanese succeeded in historically.


Air cover for a week, your words. At a distance further from Truk or Saigon who are somehow supplied better than the starving Japanese soldiers in New Guinea, Solomons, or U-Go later, and right by British bases. Still sounds like an IJA plan with total disregard for logistics.
Already covered.
Contradicted by the historical record of the Aussies as some of the best infantry in the Pacific, even the green troops in New Guinea.
So, Australians have a natural affinity for living and fighting in jungles and need no training. They did so well in Malaya. The moment they landed they just laid into the Japanese and completely out fought them. Actually the 8th Australian Division fought bravely but joined the other Commonwealth forces in a fighting withdraw that ended with their capture. What would make anyone think the 16th & 17th Brigades on Ceylon would do any better?
Except unlike shipping them back to Japan this is the opposite direction away from the source of supplies, logistics is how the Pacific war was fought.
Not the point I was making. My point was troops were available to invade Ceylon.
That's not a justification, they also thought they can invade Alaska through the Aleutians, actually tried it, and that Americans were cowards who'd sue for peace. Heck they gambled their nation on a racist delusion.
Actually, they didn't invade mainland Alaska from the Aleutians. The forces engaged in the Aleutians were fairly small because it was a diversionary operation, but I agree the whole plan was a poor idea. However, it did tie up far larger American forces for over a year.
As long as we account for starving troops and failed offensives then it's all true. They did conduct offensive operations with logistical deficits, as soon as the distance became further than a few hundred kilometers beyond their 1941 positions they stalled everywhere with starving soliders by the thousands.
That does happen when the enemy has air superiority, which would not be the case in Ceylon. In both New Guinea, and the Solomons local food resources were fairly limited, so food had to be shipped in. There was local food on Ceylon.
And with no midway the IJN would instead do something else stupid to force a "decisive battle" while ignoring the lack of anything important to the Americans within reach or their own shoddy codes. Or they would've gone with Operation FS that was historically cancelled by Midway and overreacted at a more precarious position. Anything to 'shock the Americans to surrender ' before America mobilized and crushed them.
Your analysis of Japanese planning, and capabilities seems contemptuously dismissive.
Yeah, they sank half a percentage point of American shipping capacity while Americans just replaced them. The East coast was planned and done by German captains trained in commerce raiding against a naive America, in contrast you have IJN subs trained for the decisive battle with a much smaller fleet. Given the general rule of 1/3s for naval readiness you'd need nearly half the IJN sub fleet to maintain a dozen subs in the Indian Ocean.
400,000 tons of shipping wasn't 1/2 a percentage point of American capacity. The Americans never had 80,000,000 tons of shipping. It was putting a serious crimp in Allied operations. I never said the Japanese should have 12 subs on station in the Indian Ocean. I said they should base 6 boats on Ceylon, and that the Germans should send 6 Type IX U-Boats to join them. Considering the Allied weakness in ASW forces in the Indian Ocean they could do an awful lot of damage.
With what exactly? Japan's renowned deficiency in ASW? The air fleet that only stayed for a week? The supply chain of tankers bringing AVgas to Ceylon?

Because the Japanese were known for realistic intel assessments after the Centrifugal Offensive. It's 2000 km from Burma to Ceylon beyond the range of a lot of Japanese aircraft, are the Japanese going to keep escort carriers in the bay of Bengal to ferry the planes there? Or are they going to scout and dominate an ocean with only bombers that can fly there?
Japanese intel on Ceylon & the Indian Ocean in 1942 was actually pretty good. The IJA aircraft wouldn't be coming 2,000 km from Burma, but from about half that distance from the Andaman & Nicobar Islands. Yes, bombers do dominate ocean areas when there are no enemy fighters present.
Ah yeah, the empire that managed to create uprisings and resistance movements in every land it conquered is going to get the help of the natives for any substantial period of time. They probably will initially til they realize how much crueler the Imperial Japanese were.
The Japanese don't need to win a popularity contest against the British 6 months after they land. In fact, mass panic would breakout even before they landed. That panic would've impeded Commonwealth defense efforts and still leave plenty of available manpower for their needs.
 
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