Somerville's Aggressiveness at Ceylon

Discussions on WW2 in the Pacific and the Sino-Japanese War.
Dili
Member
Posts: 2085
Joined: 24 Jun 2007 22:54
Location: Lusitania

Re: Somerville's Aggressiveness at Ceylon

Post by Dili » 09 Sep 2012 16:14

There were three strikes againt the Italian fleet off Crete on 27 March 1941. The first, with four Albacores from Formidable and a few Swordfish from Crete, made no hits. A mid-afternoon strike from Formidable (I don’t know how many Albacores were involved but probably something in the order of six to eight, scored a hit on Vittorio Veneto. The third, by six Albacores and four Swordfish, scored one hit on Pola. Victorious attacked Bismarck with nine Swordfish after dark on 24 May, in weather conditions which were much worse than on 5 April ’42 off Ceylon, and scored one hit. Ark Royal attacked Bismarck after dark on 26 May, in very bad weather which forced the 15 Swordfish to make uncoordinated attacks but they scored two hits. Together these five attacks scored five hits for about 40 drops, or just over 10%.
That was the only successful attack by carrier planes against a moving Italian fleet. There were several more attacks that achieved no hits.

glenn239
Member
Posts: 4888
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Somerville's Aggressiveness at Ceylon

Post by glenn239 » 10 Sep 2012 18:29

Each of the amphibious “jumps” the Japanese made in taking the NEI was within range of land-based aircraft.
That’s not an option here, as there are no intermediary islands to hop from Andaman to Ceylon. This would, IMO, look more like the Midway-Aleutian landings, at least in the initial phase. The amphibious components will be moving on advanced bases, the fleet components will be seeking to eliminate the British carriers and wipe out land based air power.
I would also add that Port Blair was within range of Allied aircraft. The US 10th Air Force attacked it (unsuccessfully) on the night of 2-3 April and RAAF Hudsons destroyed a number of H6Ks on 14 and 18 April. I think the Wellingtons at Calcutta could attack Port Blair as well, so it was not an entirely safe anchorage.
The foward fleet base at Staring Bay was within Allied air range throughout the period of the Southern Drive. I presume that when the carriers were at anchor their fighters were ashore so that they could provide air cover.
No Maldivian island had an airfield at the time, so your seaplane bases would have no fighter defence. The northern Maldives were within range of Wellingtons and B-24/LB-30s which could be moved fairly easily to southern India and the sourthern most atoll, Addu Atoll, had a garrison and coast defence guns, so taking it would be like taking Wake. Furthmore, your H6Ks could easily have been destroyed by a couple of hours bombardment by a light cruiser arriving at dawn.
Those conditions were true of every advanced seaplane base established by the Japanese during the southern operation. The Maldives are a perfect seaplane anchorage well placed on the flank of the main action, so I would hazard a guess they’d be taken right off for that purpose. Since this was also a secret RN base, this may lead to an accidental fleet encounter.
. Eugen Pinak suggests in Reply #56 that KdB was not taken by surprise by 11 Sqn, and this is debated, perhaps without being definitely decided, duirng the next 80 or so posts.
I followed that discussion with interest. Overall, I thought the “Fuchida” version of a surprise bombing held up.

glenn239
Member
Posts: 4888
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Somerville's Aggressiveness at Ceylon

Post by glenn239 » 10 Sep 2012 18:36

But if we’re talking about an attack on Aden, having half of KdB withdraw for replenishment to Ceylon
Aden is a discussion only if Ceylon falls. The biggest reservation I have is that it assumes the westerly concentration of Japanese naval resources well into the summer of 1942. Given the fracturous nature of the high command and their easy distraction by pinprick American carrier raids, I see it as unlikely the Japanese could have the discipline to stay focused on one strategy for that length of time.
What makes you think your ground force in Aden would not be involved in heavy gound combat? Aden is not an island. Rommel’s last attempt to advance was decisvely defeated by 27 July, after which time the British could have deployed an armoured division equipped with tanks better than any the Japanese had, plus infantry, more and better artillery
Deployed from North Africa towards Aden via the Suez you mean? But if the Japanese have cut the Aden route with their naval power, and the Axis hold Libya and Sicily, what is the supply route for the Desert Force?
While there were a number of airfields in southern India within range of Ceylon, I don’t think any of them were on the coast.
The key factor is IJA amphibious assault doctrine, which called for strong points of resistance to be bypassed in the first waves if at all possible. These instead would land at poorly defended areas to take forward air bases. These air fields might be military or civilian, large or small. I would assume that the IJA would know every field on Ceylon, even the tiny ones. You’re saying that Ceylon itself was a tough nut to crack with most of the military fields concentrated (and therefore easily defended). As per IJA doctrine, then I would predict their preference would be to land in India to seize air bases that were not so heavily defended. Then, use them to isolate and establish air superiority over Ceylon, so that its beaches could be closely studied.

If this was not an option, by what you are describing a direct assault upon Ceylon looks like a dicer proposition and the Japanese may be deterred from trying simply on the basis of the risk. The Japanese were willing to make direct assaults for strategic assets, but I doubt they’d consider Ceylon sufficiently important. If they did land, it would be at a lightly defended place on Ceylon and then the force would march overland. Naval gunfire support I think we can safely dismiss – the navy often gave support during landings, but once ashore the coordination was totally lacking.
Okay, I’ll concede that portions of KdB could withdraw to Port Blair (700 NM from Trincomalee, about 900 from Colombo) in turn to replenish. Let’s assume that four CVs were committed. The 1400 NM round trip from Trincomalee would take four days, plus probably two days to replenish, so six days. The two carriers left off Ceylon could easily expend all their bombs during those six days and need to make tracks for Port Blair as soon as the first two returned, so most of the time there would be only two CVs off Ceylon. They would have to stay in range of the beachhead, so the British would have a good idea where they were and Somerville, with Indomitable, Formidable and Illustrious and their 65 torpedo bombers, might have been able to pull off the night torpedo attack he tried to do on 5 April.
Assuming similar practices to the southern drive, the main amphibious assault will not occur until the forward land bases have been captured that provide air cover. Like a spider in the web, Nagumo's strike force would lurk within than umbrella looking to pounce. If this forward air cover was not established, I doubt they would launch the main invasion.
Won’t work. The British were not going to divert anything from Ceylon to counter a landing up near Burma, because they considered Ceylon far more important.
But if there was a possibility of cutting off and annihilating the British Burma army, then this could become the focus of the whole Japanese Indian Ocean offensive. How safe were the lines of communication to Burma, assuming the Japanese were willing to land around Calcutta or some other place to cut them?

Rob Stuart
Member
Posts: 994
Joined: 18 Apr 2009 00:41
Location: Ottawa

Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 10 Sep 2012 23:46

That was the only successful attack by carrier planes against a moving Italian fleet. There were several more attacks that achieved no hits.
Dili,

I was not aware of these attacks but now I see in Harrison's Fairey Swordfish and Albacore that two strikes, of 11 and then 9 Swordfish, attacked the Italian fleet without success on 27 November 1040, so you're right.

If you're implying that my 10% hit rate is too high, that's not impossible. But there is also the fact that an attack by 30+ Albacores on 5 April would have been two to three times larger than the attacks of 1940-1941, and I think that larger forces tended to have a higher hit rate than smaller forces, especially if an early drop secured a damaging hit, as happened to Prince of Wales.

Rob

Carl Schwamberger
Host - Allied sections
Posts: 6947
Joined: 02 Sep 2006 20:31
Location: USA

Re: Somerville's Aggressiveness at Ceylon

Post by Carl Schwamberger » 11 Sep 2012 02:01

I wonder which would have been worse for the Japanese fleet: The Albacores arriving more less together & 30+ of them attacking within the same few minutes against a fleet back lit by flares? Or, attacking one or two every minute for 20-30 minutes, from different directions, and flares overhead only part of the time?

Rob Stuart
Member
Posts: 994
Joined: 18 Apr 2009 00:41
Location: Ottawa

Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 11 Sep 2012 02:05

Glenn, here we go again:
Me: Each of the amphibious “jumps” the Japanese made in taking the NEI was within range of land-based aircraft.

You: That’s not an option here, as there are no intermediary islands to hop from Andaman to Ceylon. This would, IMO, look more like the Midway-Aleutian landings, at least in the initial phase. The amphibious components will be moving on advanced bases, the fleet components will be seeking to eliminate the British carriers and wipe out land based air power.
I agree, an attack on Ceylon would be like the plan for Midway – and we all know what happened on 4 June when KdB tried to accomplish two missions: softening up Midway and destroying the US carriers. My point was that the Japanese would need to seize a Ceylonese airfield right away, so that KdB could be free to withdraw or to chase the EF.

Me: I would also add that Port Blair was within range of Allied aircraft. The US 10th Air Force attacked it (unsuccessfully) on the night of 2-3 April and RAAF Hudsons destroyed a number of H6Ks on 14 and 18 April. I think the Wellingtons at Calcutta could attack Port Blair as well, so it was not an entirely safe anchorage.

You: The foward fleet base at Staring Bay was within Allied air range throughout the period of the Southern Drive. I presume that when the carriers were at anchor their fighters were ashore so that they could provide air cover.
The difference was that the airfields at Kendari were large enough to accommodate all of KdB’s aircraft. The airstrip at Port Blair was tiny with room for only a few Zeros. As well, the attacks I refer to were night attacks.

Me: No Maldivian island had an airfield at the time, so your seaplane bases would have no fighter defence. The northern Maldives were within range of Wellingtons and B-24/LB-30s which could be moved fairly easily to southern India and the sourthern most atoll, Addu Atoll, had a garrison and coast defence guns, so taking it would be like taking Wake. Furthmore, your H6Ks could easily have been destroyed by a couple of hours bombardment by a light cruiser arriving at dawn.

You: Those conditions were true of every advanced seaplane base established by the Japanese during the southern operation. The Maldives are a perfect seaplane anchorage well placed on the flank of the main action, so I would hazard a guess they’d be taken right off for that purpose. Since this was also a secret RN base, this may lead to an accidental fleet encounter.


The difference was that these previous advanced seaplane bases were not nearly as far ahead of the advancing forces and so exposed to attack as one in the Maldives would be. Heavens, even Hermes could have taken it out.

Me: What makes you think your ground force in Aden would not be involved in heavy gound combat? Aden is not an island. Rommel’s last attempt to advance was decisvely defeated by 27 July, after which time the British could have deployed an armoured division equipped with tanks better than any the Japanese had, plus infantry, more and better artillery

You: Deployed from North Africa towards Aden via the Suez you mean? But if the Japanese have cut the Aden route with their naval power, and the Axis hold Libya and Sicily, what is the supply route for the Desert Force?
The interruption, if any, to the supply route around the cape and up the east coast of Africa would be brief. After the Allied naval and air forces decimated (or repulsed) the landing forces, the latter might be too weak to even seize Aden against a forewarned and reinforced garrison, and if they did the airfield would be out of service. The attacking detachment from 8th Army would not even have to retake Eden, it would only need to bring the airfield and harbour within range of its artillery. A few batteries of 25-pounders (range 12 km) would keep the airfield and its AA guns out of action, and then the minesweepers would be sunk. With no operational airfield and its naval force bottled up, the Japanese base at Aden would be in the same situation as Rabaul was after it was bypassed – irrelevant.

You: The key factor is IJA amphibious assault doctrine, which called for strong points of resistance to be bypassed in the first waves if at all possible. These instead would land at poorly defended areas to take forward air bases.
There were no poorly defended areas in the vicinity of forward air bases. In Malaya there were more airfields than the British could defend but this was not true in Ceylon.

You: I would assume that the IJA would know every field on Ceylon, even the tiny ones.


Nope. According to Monograph 118, the only Ceylonese airfields the Japanese knew of were Colombo, Trincomalee and Puttalam, the latter being a small strip 75 miles north of Colombo. (It could have been approached only by sailing north past Colombo, which would therefore have to have been attacked first or simultaneously.) The historical air attack of 5 April did not attack the Racecourse airfield (home of one Hurricane unit and one Blenheim unit) nor the Catalina base at Koggala, and the 9 April attack did not attack China Bay’s satellite field 35 miles to the NNW.

You: As per IJA doctrine, then I would predict their preference would be to land in India to seize air bases that were not so heavily defended. Then, use them to isolate and establish air superiority over Ceylon, so that its beaches could be closely studied.
The only southern Indian airfields mentioned in Monograph 113 are Madras (280 NM from Trincomalee, 370 from Colombo), Bangalore (150 miles inland!), “Trichinoply” (prob. Tiruchchirappalli, 65 miles inland) and Quilon (on the southwest coast but 225 miles from Colombo, 275 from Trincomalee). Quilon would really be the only candidate but it’s too far away for Kates or Vals to effectively support operations on Ceylon. Furthermore, if the Ceylon invasion was to be hard on the heels of Operation C then the landing force needed to take it would be a significant portion of the two IJA divisions available.

Me: Won’t work. The British were not going to divert anything from Ceylon to counter a landing up near Burma, because they considered Ceylon far more important.

You: But if there was a possibility of cutting off and annihilating the British Burma army, then this could become the focus of the whole Japanese Indian Ocean offensive. How safe were the lines of communication to Burma, assuming the Japanese were willing to land around Calcutta or some other place to cut them?
Make up your mind, are they going for Ceylon or Bengal? Going for Bengal would mean a lengthy delay, because the two IJA divisions available in April to invade Ceylon were the two sealifted from Singapore to Rangoon between 19 March and 7 April. If they were instead landed near Calcutta they would have been cut off, since without them the Burma army would be too weak to reach them overland.


Rob

Carl Schwamberger
Host - Allied sections
Posts: 6947
Joined: 02 Sep 2006 20:31
Location: USA

Re: Somerville's Aggressiveness at Ceylon

Post by Carl Schwamberger » 11 Sep 2012 17:51

glenn239 wrote:
Deployed from North Africa towards Aden via the Suez you mean? But if the Japanese have cut the Aden route with their naval power, and the Axis hold Libya and Sicily, what is the supply route for the Desert Force?
One possibility is a larger threat against the Indian Ocean route to the Middle East/Egypt would be actually executing Operation Gymnast, with the intent of attacking Sicilly ASAP. A gamble yes, but the perception of sufficient pressure in the IO might trigger such a move. With the Japanese fleet less active in the Pacific & the OTL sense of emergency there lessened. The resources historically unavailable for Op Gymnast may then be seen as not needed in the South Pacific. Lacking the four carrier battles of the 1942 PTO USN losses would be fewer and very likely two more carriers, surface ships, a corps of ground forces, several USAAF air groups, and a fair sized slice of cargo ships would remain situated for use in the west as originally planned in early 1942.

glenn239
Member
Posts: 4888
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Somerville's Aggressiveness at Ceylon

Post by glenn239 » 11 Sep 2012 19:27

Furthermore, if the Ceylon invasion was to be hard on the heels of Operation C....
I assume any major offensive waits until June 1942, after 1st Phase operations were complete, the divisions participating in these were replenished, and Kido Butai had refitted in Japan.
Make up your mind, are they going for Ceylon or Bengal?
We’re discussing an attack on Ceylon after May 1942, but that is with an explicit assumption the British position in the north is not so exposed that the Japanese become tempted to try for the destruction of the British army in Burma instead.
Nope. According to Monograph 118, the only Ceylonese airfields the Japanese knew of were Colombo, Trincomalee and Puttalam, the latter being a small strip 75 miles north of Colombo. (It could have been approached only by sailing north past Colombo, which would therefore have to have been attacked first or simultaneously.
So intel was poor about Ceylon, and the distance also looks too far for standard IJA recce aircraft. IJN seaplanes are too vulnerable, meaning that 1st Phase ops will have poor intel.
I agree, an attack on Ceylon would be like the plan for Midway – and we all know what happened on 4 June when KdB tried to accomplish two missions: softening up Midway and destroying the US carriers. My point was that the Japanese would need to seize a Ceylonese airfield right away, so that KdB could be free to withdraw or to chase the EF.
The invasion of Ceylon presumably happens in two phases, like the invasion of Luzon. In the first phase numerous smaller forces would seize forward airfields that were either poorly defended or not defended at all, and seaplane bases would also be set up. Kido Butai’s primary mission would be, like at Midway, divided between smashing land based airpower and the RN’s offensive forces. Like at Midway, the division of attention between tasks creates risk in the form of tactical compromise that might see an RN counterattack succeed. Assuming the 1st Phase operations are successful, then the main invasion would occur next, under the umbrella of the 1st phase positions. By that time, intel on Ceylon would be vastly improved by way of direct observation. If the 1st Phase ops are not successful, then the actual invasion is delayed or cancelled.
The difference was that the airfields at Kendari were large enough to accommodate all of KdB’s aircraft. The airstrip at Port Blair was tiny with room for only a few Zeros.
Everything about Staring Bay was better. The first thing I'd assume the IJN would do would be to survey every possible location from Padang to Rangoon and decide from there. I would not think a marginal long range air threat by the occassional bomber would be the primary fear. I would assume they’d be much more concerned about submarines.
The difference was that these previous advanced seaplane bases were not nearly as far ahead of the advancing forces and so exposed to attack as one in the Maldives would be.
I don’t see the Maldives exposed geographical position being a deterrent. If you are looking at a Japanese invasion of Ceylon, and you are using actual Japanese doctrine on how to conduct such operations, you should assume the Japanese will go there in the first wave. They assumed the island group was practially abandoned, so it is (doctrinally) a perfect target.

Rob Stuart
Member
Posts: 994
Joined: 18 Apr 2009 00:41
Location: Ottawa

Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 12 Sep 2012 00:44

Glenn,
I assume any major offensive waits until June 1942, after 1st Phase operations were complete, the divisions participating in these were replenished, and Kido Butai had refitted in Japan.
So, no Operations MO or MI/AL, right? Well then, by June Ceylon will have received more reinforcements, particularly radar, AA guns, AT guns and fighters, and will be a harder nut to crack than in April. Also, the occupation of Diego Suarez was completed in early May, so Somerville could have had three carriers. Nimitz would have five - Lexington, Saratoga (it missed Midway by only a few days), Yorktown, Enterprise and Hornet. The Japanese thought that one of their subs had sunk a Lexington-class ship, in the attack that damaged Saratoga, but knew that Wasp was available too, so they would have known that the US could have had five carriers at Pearl. Even if they stand on the defensive in the Pacific so that they can move east, in the wake of the Doolittle raid they'll have to retain several carriers in the Pacific. I doubt that they'd retain only two when the US had five, so they may only be able to detach one CarDiv from KdB plus their light carriers to the IO, which they would presumably see as not enough. To sum up, they had a window of opportunity in April but not in June, unless they first knock out a few US carriers.



The invasion of Ceylon presumably happens in two phases, like the invasion of Luzon. In the first phase numerous smaller forces would seize forward airfields that were either poorly defended or not defended at all, and seaplane bases would also be set up. Kido Butai’s primary mission would be, like at Midway, divided between smashing land based airpower and the RN’s offensive forces. Like at Midway, the division of attention between tasks creates risk in the form of tactical compromise that might see an RN counterattack succeed. Assuming the 1st Phase operations are successful, then the main invasion would occur next, under the umbrella of the 1st phase positions. By that time, intel on Ceylon would be vastly improved by way of direct observation. If the 1st Phase ops are not successful, then the actual invasion is delayed or cancelled.
My point was not so much that there were vulnerable airfields the Japanese did not know about, it was that there were none. There could therefore be no 1st and 2nd Phase landings as you've described them. Only the main landings would be strong enough to seize either of the two air bases worth taking.


Rob

glenn239
Member
Posts: 4888
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Somerville's Aggressiveness at Ceylon

Post by glenn239 » 12 Sep 2012 19:48

So, no Operations MO or MI/AL, right?
Right. The Japanese had the strength to take an offensive in one direction, not more. Any division of effort into multilple advancing fronts would lead to the high chance of failure on all of them. The premise for Ceylon pretty much has to be a fully focused effort, like the taking of Java was a focused effort. Anything less would probably putter out into a British victory.
Nimitz would have five - Lexington, Saratoga (it missed Midway by only a few days), Yorktown, Enterprise and Hornet.
To be clear – any prospect for success in the Indian Ocean by Japan is predicated by the US carriers staying well clear. If US carriers go west, all bets are off.
My point was not so much that there were vulnerable airfields the Japanese did not know about, it was that there were none. There could therefore be no 1st and 2nd Phase landings as you've described them.
Japanese aircraft were light, meaning their operational footprint was also quite light. During the southern operation it seemed the case that pretty much any major city would also have a civilian airfield or two of some description, and these civilian airports were often adequate for military use. You indicate poor IJA intel on civilian fields, but if there was a city, chances were there was also a civilian airfield of some decription. Even a road could work as a make-shift airfield, and I assume southern India had a full road net. So I did not assume there are no 1st wave targets of places suitable to operate aircraft, lightly defended. Did the British have paved roads in India? One factor not yet discussed would be the wet season, which starts around June. Monsoons would negatively effect all operations.

Rob Stuart
Member
Posts: 994
Joined: 18 Apr 2009 00:41
Location: Ottawa

Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 13 Sep 2012 02:56

To be clear – any prospect for success in the Indian Ocean by Japan is predicated by the US carriers staying well clear. If US carriers go west, all bets are off.
The US carriers will not stay clear. At a minimum they will continue to carry out raids of the sort they started in February and with five carriers available by mid-June they could get quite ambitious, maybe raiding Rabaul or somewhere else important. I think the Japanese could have decided to adopt a western strategy in 1942, for example if the Germans first broke through in the Middle East, but they would have to break the back of the US carrier force first, so as to secure their eastern flank. This would mean no Operation MO but there would have to have been an Operation MI or an operation of some other sort which would allow the US carriers to be dealt with, before heading west.

Rob

glenn239
Member
Posts: 4888
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Somerville's Aggressiveness at Ceylon

Post by glenn239 » 13 Sep 2012 20:38

The US carriers will not stay clear.
Noted, but my personal opinion is that I don’t think this will happen. The US Navy was set on Rainbow Five, and Rainbow Five was all about glorious US Navy offensives towards the Marshalls, not pulling British chestnuts from the fire in the far off Indian Ocean.

I believe the main issue may be the monsoon season. An operation before June really wasn’t in the cards (IMO), and one after June put matters in the rainy season. Civilian airfields and makeshift road airfields were all well and good, but if the ground were a soggy morass that would be seriously impeding to Japanese operations.

Rob Stuart
Member
Posts: 994
Joined: 18 Apr 2009 00:41
Location: Ottawa

Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 14 Sep 2012 17:53

Me: The US carriers will not stay clear.

Glenn: Noted, but my personal opinion is that I don’t think this will happen. The US Navy was set on Rainbow Five, and Rainbow Five was all about glorious US Navy offensives towards the Marshalls, not pulling British chestnuts from the fire in the far off Indian Ocean.
Surely it was clear that what I meant was that the US carriers are not going to sit at Pearl doing nothing. I said they might raid Rabual or somewhere else important. The Marshalls would do quite nicely! If all the Japanese carriers go to the IO, then the US carriers can raid Japanese outposts to their hearts' content. (Why would they suddenly stop raiding?) If half the Japanese carriers stay in the Pacific while the other are in the IO, the USN will go after the ones still in the Pacific. Either way, they won't see that as pulling anyone's chestnuts out of the fire, they'll see it as an opportunity.

I believe the main issue may be the monsoon season. An operation before June really wasn’t in the cards (IMO), and one after June put matters in the rainy season. Civilian airfields and makeshift road airfields were all well and good, but if the ground were a soggy morass that would be seriously impeding to Japanese operations.
It’s not at all clear why you think an invasion of Ceylon is not in the cards before June. Can you explain?

As for the monsoon, you’re referring to the southwest monsoon, which typically lasts from June to October. (The northeast monsoon is December to March.) I don’t know very much about the impact of monsoons on operations in the Bay of Bengal, but they certainly affected land operations in Burma. Naval operations off Burma were evidently also affected, based on the following comment in the East Indies Fleet war diary (http://www.naval-history.net/xDKWD-EF1945.htm) regarding the retaking of Rangoon in May 1945:

As soon as they could be spared, all major landing craft were withdrawn to Indian ports in order to be clear of the lee shore before the south west monsoon became established.

As for naval operations off Ceylon, I have found the following:

A March 1942 comment by Admiral Layton (from http://www.naval-history.net/xDKWD-EF19 ... tation.htm), with the underlining added by myself:

4. It is valueless to mine the South and West Coasts of Ceylon until after the end of the S.W. Monsoon. The following trial local operations have been considered.

a). To satisfy Army wishes by mining off possible invasion beaches on the East Coast of Ceylon and by mining Palk Strait.

[…]

b). To lay deep trap minefields to seaward of the coastal route off the East coast of Ceylon to catch enemy submarines operating against coastal traffic.


An April 1942 report from the C-in-C East Indies (see http://www.naval-history.net/xDKWD-EF1942a.htm) includes the following passage, with the underlining added by myself:

Merchant Shipping

2. The Japanese threat to Calcutta and the east coast of India made it necessary to limit shipping on that coast to essential cargoes. On the 16th April, I appreciated the situation as follows:

(a) Colliers, tankers, and important war cargoes have still to pass along the east coast of India.

(b) The submarine menace on the east coast of India cannot be discounted, especially during the south west monsoon which renders the calmer waters of the east coast favourable to the tactics of the Japanese U boat.

(c) Troop convoys on the African coast and between Bombay and Africa, Middle East, or Basra are likely to continue and absorb all the ocean escorts

(d) The recurrence of German and the appearance of Japanese raiders in the Indian Ocean must be considered a growing likelihood.

(e) Weather conditions during the south west monsoon will hamper the assembly of convoys in the open roadsteads on the west coast of India, and if the existing harbour congestion continues May even frustrate them.


I would infer from these comments that a landing on the west or south coasts of Ceylon (e.g., at Colombo) would be impractical between June and October, but possible on the east coast (e.g., at Trincomalee). I presume that there might still be problems, such as getting the invasion fleet out of Burmese ports or providing air support, which would prompt the Japanese to avoid invading the island between June and October. But to my mind this is somewhat moot. The possible invasion was debated in February. Had it been approved, instead of the plan to isolate Australia, then it would have been executed in April-May. You seem to be saying that Operation C would have been conducted as it actually was, and then for some reason there would be a pause of several weeks, then the IJN would return to the IO and take Ceylon just ahead of the southwest monsoon. I think any such pause can be ruled out. The Japanese knew the importance of keeping their enemies off balance, which meant keeping up the pressure. Either the invasion of Ceylon would be right after the historic Operation C, with landings perhaps starting as early as 12 April, or they would deal with the Americans between May and July before turning back.

Rob

glenn239
Member
Posts: 4888
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Somerville's Aggressiveness at Ceylon

Post by glenn239 » 14 Sep 2012 18:56

You seem to be saying that Operation C would have been conducted as it actually was, and then for some reason there would be a pause of several weeks, then the IJN would return to the IO and take Ceylon just ahead of the southwest monsoon.
I’m saying that all along I have assumed any Indian Ocean offensive to be a genuine 2nd Phase operation taken after the 1st Phase was completed and Kido Butai rested and 1st Phase divisions replenished, not as an afterthought tacked on to the 1st Phase. I did not realise monsoon season began in June, but knowing that now I have my doubts there would be any offensive launched during it.
If all the Japanese carriers go to the IO, then the US carriers can raid Japanese outposts to their hearts' content. (Why would they suddenly stop raiding?)
Indeed, but these raids were pretty much irrelevant in a strategic sense and dangerous to US carriers tactically. So if Japan were concentrating on another front, the Americans could safely be ignored. Using land based air power and submarines, such raids were an opportunity to inflict attrition on the US carriers at little risk.

Rob Stuart
Member
Posts: 994
Joined: 18 Apr 2009 00:41
Location: Ottawa

Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 15 Sep 2012 13:57

I’m saying that all along I have assumed any Indian Ocean offensive to be a genuine 2nd Phase operation taken after the 1st Phase was completed and Kido Butai rested and 1st Phase divisions replenished, not as an afterthought tacked on to the 1st Phase.
Yes, you’ve said all along that this pause was needed but haven’t really explained why it was so vital. Now you say it’s so that KdB can rest and so that the army’s 1st Phase divisions can be replenished. I don’t think this holds water. Akagi arrived at Staring Bay on 9 March, and Soryu and Hiryu arrived there on 11 March. They rested and trained there until 26 March. Shokaku and Zuikaku joined them on 24 March, having been in the homeland for rest and maintenance from 3 February to 7 March and 13 February to 4 March, respectively. As for the army divisions, I would see the 18th and 56th Divisions being used for the invasion. The former was in the Malayan campaign and therefore not involved in operations after 15 February. The 56th Division was newly formed. Its 56th Brigade fought in the NEI in January but possibly not after that. The Imperial Guards Division was perhaps also a possibility. It became free on 28 March when the last Dutch forces in northern Sumatra surrendered. Its 12-28 March campaign does not seem to have been very costly or exhausting. So I don’t see any great need for either the IJN or the IJA forces required for the invasion to rest or replenish until June. They were ready in April. The only obstacle I can see to going in April is a possible lack of shipping. It certainly looks like there was sufficient shipping in the area to lift one division at a time. This may have been enough, but if the Japanese decided they needed to land both divisions at the same time then finding the extra ships might have imposed a delay, but probably not as long a delay as you suggest.

I would point out that the Ceylon operation was wargamed aboard Yamato from 20 to 22 February. By about 7 March the idea was abandoned but had it been approved by the end of February it could have been mounted in April, if the Army was willing to use the 18th and 56th Divisions instead of moving them to Burma. Four to six weeks is not a lot of time to get ready, but both MO and WATCHTOWER were launched on such short notice, so should have been enough.

Me: If all the Japanese carriers go to the IO, then the US carriers can raid Japanese outposts to their hearts' content. (Why would they suddenly stop raiding?)

Glenn: Indeed, but these raids were pretty much irrelevant in a strategic sense and dangerous to US carriers tactically. So if Japan were concentrating on another front, the Americans could safely be ignored. Using land based air power and submarines, such raids were an opportunity to inflict attrition on the US carriers at little risk.
I’m surprised that you would suggest that the Japanese would ignore the US raids. After all, the 18 April Doolittle raid gave Yamamoto the argument he needed to get his MI plan approved. You’re suggesting that the Japanese would launch their IO offensive in June, monsoons permitting, without first going after the US carriers or at least retaining enough carriers in the Pacific to protect the homeland from another raid. I don’t think that’s very likely.

The frustrating thing about our little debate here is that were both just speculating. It’s a shame that no details are available, in English anyway, about the 20-22 February war game and the related planning. Surely the question of when the operation might have been mounted was discussed.


Rob

Return to “WW2 in the Pacific & Asia”