Somerville's Aggressiveness at Ceylon

Discussions on WW2 in the Pacific and the Sino-Japanese War.
Tom from Cornwall
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Re: Somerville's Aggressiveness at Ceylon

Post by Tom from Cornwall » 09 Jul 2020 20:22

Rob Stuart wrote:
07 Jul 2020 14:11
Churchill relates in his memoirs that, in a 5 March message to Roosevelt, he expressed the hope that, with Ceylon-based British and Dutch submarines watching the Malacca Straits and US submarines patrolling the Sundra Straits and other exits between NEI islands, “we should not only get notice of, but be able to take a toll of, any Japanese forces breaking out into the Indian Ocean. The next fortnight will be the most critical for Ceylon, and by the end of March we ought to be solidly established there, though by no means entirely secure.”

I would say that KdB's passage toward Ceylon was missed because it passed through the Malay Barrier via the Ombai Strait, which was not being watched by any Allied sub, and that it was missed during its return to Japan through the Malacca Strait because Truant had been ordered to stay on station for only seven days and had already departed for Colombo. (Trusty arrived in the northern approaches to the Malacca Strait on 18 April.)
Rob,

I found this snip in the Patrol Report of USS Seawolf which was having a busy patrol:
Seawolf narrative - 27-28 Mar 42.GIF
So it looks like she was covering the Sunda Strait until ordered by her shore HQ to head towards Christmas Island. Interesting to see where the other US submarines were deployed at that time - I'll have a look at a few more to see if I can dig that out.

Regards

Tom
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cstunts
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Re: Somerville's Aggressiveness at Ceylon

Post by cstunts » 10 Jul 2020 02:30

There is nothing revelatory in this, however. Our submarines (formerly Asiatic Fleet, I guess, in this case) were certainly being positioned according to sigint, and that also meant--I presume--Station Cast on Corregidor. Virtually ALL of our sub patrol reports from the first months of the war in the SWP show these types of secret messages indicating new hunting grounds, in effect.

It is interesting that both SEAWOLF and TRUANT (belatedly) had been vectored out to the Bali Strait area earlier in Feb. 1942 in an attempt to counter the IJN invasion, but w/no success in obstructing those ops.
SEAWOLF got into position in time & had visible contact, but the weather and the extremely problematic currents in the straits made her efforts futile. I think TRUANT arrived too late and was closer perhaps to Lombok Strait, but had no luck either as far as stopping the Japanese went.

However, the business with SEAWOLF at Xmas I. in late March resulted in the torpedoing of the IJN light cruiser NAKA during invasion ops on that island.

Tom from Cornwall
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Re: Somerville's Aggressiveness at Ceylon

Post by Tom from Cornwall » 10 Jul 2020 09:20

cstunts wrote:
10 Jul 2020 02:30
There is nothing revelatory in this, however.
No, but I found it interesting and thought others might too.
cstunts wrote:
10 Jul 2020 02:30
Virtually ALL of our sub patrol reports from the first months of the war in the SWP show these types of secret messages indicating new hunting grounds, in effect.
Same for Allies in Europe (certainly in the Mediterranean) and U-boats too, at least while the Germans were breaking the Allied (British?) convoy codes.

It would be interesting to know what information the Japanese had about Allied submarine movements at this point and whether this contributed to their disappointing results.

Regards

Tom

Rob Stuart
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Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 12 Jul 2020 15:43

Tom from Cornwall wrote:
10 Jul 2020 09:20
It would be interesting to know what information the Japanese had about Allied submarine movements at this point and whether this contributed to their disappointing results.
The Japanese were unable to read any important Allied codes or ciphers, so they could not predict where Allied submarines might appear (apart from assuming that they would congregate at certain obvious choke points). My understanding is that after arriving in their assigned patrol areas Allied subs maintained radio silence until they made their first attack or until they had something important to report, such as the sighting of a convoy or a large warship. So I would say that Japanese foreknowledge of Allied submarine movements was negligible and that the reasons for the disappointing results realized by Allied subs from December 1941 to say the end of April 1942 included the following:

(1) Changes made to JN-25 in December 1941 meant that Japanese naval and mercantile movements could not be foreseen through Comint until near the end of the period.

(2) Priority targets for the in-theatre Allied subs were invasion convoys. Since Comint could not predict where the landings would take place, the subs had to be dispersed to cover several possible landing sites. Those sent to the wrong places had no chance to sink anything, while those which did encounter invasion forces found them strongly escorted and often accomplished little.

(3) The US had the largest sub fleet but also the worst torpedoes - and at first did not know it. The Asiatic Fleet subs were also short of torpedoes, due in part to some of their stockpile being lost in Japanese air raids.

(4) A high proportion of the US and Dutch subs were old. Trusty and Truant were modern boats but they did not arrive in the theatre until mid-January and early February, respectively, and seem to have had a comparatively low endurance.

(5) Allied sub bases were successively abandoned, which disrupted sub maintenance and operations.

(6) Several US subs had to be diverted to the task of running supplies to the Philippines and bringing out key people.

(7) US sub doctrine and the caution exhibited by some of the skippers (several of whom were relieved of their commands) contributed to the ineffectiveness of some of the attacks, e.g., firing torpedoes from below periscope depth based solely on bearings from sonar.

EwenS
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Re: Somerville's Aggressiveness at Ceylon

Post by EwenS » 13 Jul 2020 12:36

The T class boats were designed for a 42 day patrol period. Range was 8000 at 10kts (max 15.25) which was presumably their most economical speed on the surface.

Looking at Trusty (I can’t access Truant on U-boat.net at present) she was out from Colombo for only 18 days, leaving 13 April and returning 30 April. Colombo to the patrol area is approx 1200 miles or 5 days on the surface at 10 knots but probably longer as they would be diving at some point each day for trim checks etc. None of her patrols around this time exceeded about 21 days. Mind you conditions in these boats in the tropics was not pleasant. So it appears that it was standard operating procedure rather then range limitation.

It was only later in the war that their endurance was improved to 11,000 miles by putting oil in the external ballast tanks. The longest patrol in a T boat was 56 days (40 in the patrol area) by Tantalus sometime in 1944/45.

By way of comparison, USS Seawolf was designed for 11,000 miles range at 10 knots (max speed surfaced 21 knots). Her patrols at this time were 51-53 days long.

Tom from Cornwall
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Re: Somerville's Aggressiveness at Ceylon

Post by Tom from Cornwall » 13 Jul 2020 19:35

Rob Stuart wrote:
12 Jul 2020 15:43
So I would say that Japanese foreknowledge of Allied submarine movements was negligible and that the reasons for the disappointing results realized by Allied subs from December 1941 to say the end of April 1942 included the following:
Rob,

Thanks - one, at least, of the US patrol reports is brutally honest in admitting that the CO had fouled up getting into a good firing position and then fired without re-positioning. So some inexperience all round as well, no doubt.
EwenS wrote:
13 Jul 2020 12:36
The T class boats were designed for a 42 day patrol period. Range was 8000 at 10kts (max 15.25) which was presumably their most economical speed on the surface.

Looking at Trusty (I can’t access Truant on U-boat.net at present) she was out from Colombo for only 18 days, leaving 13 April and returning 30 April. Colombo to the patrol area is approx 1200 miles or 5 days on the surface at 10 knots but probably longer as they would be diving at some point each day for trim checks etc. None of her patrols around this time exceeded about 21 days. Mind you conditions in these boats in the tropics was not pleasant. So it appears that it was standard operating procedure rather then range limitation.
Thanks for that information - I wonder if there was also concern over the material state of Trusty and Truant at such range from any dockside support. Truant was specifically told only to spend 7 days on station, IIRC.

Regards

Tom

EwenS
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Re: Somerville's Aggressiveness at Ceylon

Post by EwenS » 13 Jul 2020 22:19

Trusty had only been completed in July 1941 and this was only her 5th war patrol. So not an old boat by any stretch of the imagination. British subs were generally reliable mechanically until they got a bit of age about them. Truant on the other hand had been in service for two and a half years and had led an active war in the North Sea and Mediterranean before being transferred to the Far East.

Rob Stuart
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Re: Somerville's Aggressiveness at Ceylon

Post by Rob Stuart » 15 Jul 2020 15:58

Rob Stuart wrote:
07 Jul 2020 14:11
I would say that KdB's passage toward Ceylon was missed because it passed through the Malay Barrier via the Ombai Strait, which was not being watched by any Allied sub [...]
When I wrote the above I overlooked the related movements of the USS Sculpin:

13 March: Sculpin departs from Fremantle at 1745 for a patrol off Mindanao.

17 March: Sculpin surfaces at 1923, receives CSAF 171125, directing it “to proceed direct to Staring Bay arriving prior 24th if possible.”

23 March: Sculpin receives CSAF 231023, “announcing probable presence major units enemy fleet in Staring Bay area.”

24 March: Sculpin completes SW-NE passage of Ombai Strait at 0345, heads north, submerges at 0432. It surfaces at 1844 and receives CSAF 241400, “stating that carriers may not arrive Staring Bay prior twenty-sixth.”

25 March: Sculpin arrives off southeastern approaches to Staring Bay and remains in the area until 17 April.

26 March: Sculpin submerges at 0439, patrols at periscope depth covering Eastern approaches to Staring Bay but has no contacts. It surfaces at 1850 and receives CSAF 261444, which directs it to patrol Staring Bay approaches south of Greyhound Strait until further orders.

(Sources:

Blair, Clay, Silent Victory, The U.S. Submarine War Against Japan, vol. 1, Lippincott, 1975, pp. 168-9.

Mendenhall, Corwin, Submarine Diary:The Silent Stalking of Japan, Naval Institute Press, 1991, p. 53-57

USS Sculpin Report of Third War Patrol, at http://issuu.com/hnsa/docs/ss-191_sculpin?mode=a_p

August 2010 posts by Luke G.A. Ruffato archived at http://www.j-aircraft.org/smf/index.php ... 9#msg70939. Also a 13 March 2010 by Luke accessed at http://www.j-aircraft.org/smf/index.php?topic=8980.0. which I can no longer find.)


Clearly the Allies knew that KdB was at Staring Bay and that CarDiv5 was arriving there on 24 March, although much of this intelligence may have been from traffic analysis rather than reading JN-25B.

Sculpin did not arrive off Staring Bay until 25 March, so it had no opportunity to attack Zuikaku and Shokaku when they arrived on 24 March. Sculpin's patrol report gives the position at which it submerged at first light on 26 March and by my very rough estimate this position was up to 50 nm east of KdB track when it sortied that morning. Sculpin was too far away to see or hear KdB go by.

With hindsight one might say that it would have been better if Sculpin had been ordered to patrol the Ombai Strait, as it's only some 16 nm wide at its narrowest point, but the Allies did not know in mid-March that KdB had been ordered to proceed to Ceylon. In fact, Blair says that at this time King was anticipating a possible invasion of Australia, in which case KdB was not necessarily going to use Ombai Strait.

It's unfortunate (or lucky, depending on your point of view) that Sculpin did not at least sight and report KdB's departure. When the British realized that an attack on Ceylon was imminent, they thought that it would happen on 1 April because they did not know that the planned 21 March departure from Staring Bay had been postponed. Had Sculpin reported KdB's 26 March departure the British would have worked out that it would be arriving circa 5-7 April.

Tom from Cornwall
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Re: Somerville's Aggressiveness at Ceylon

Post by Tom from Cornwall » 15 Jul 2020 19:36

Rob Stuart wrote:
15 Jul 2020 15:58
It's unfortunate (or lucky, depending on your point of view) that Sculpin did not at least sight and report KdB's departure. When the British realized that an attack on Ceylon was imminent, they thought that it would happen on 1 April because they did not know that the planned 21 March departure from Staring Bay had been postponed. Had Sculpin reported KdB's 26 March departure the British would have worked out that it would be arriving circa 5-7 April.
Rob,

Many thanks for following up and posting this interesting information.

As you say though, it is debateable whether anything that made it more likely for Somerville's force to actually gain contact with the Japanese force would have been a good thing for the Allies (and especially the RN) or not.

I take it that CSAF = Commander Submarines Asiatic Fleet?

Regards

Tom

cstunts
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Re: Somerville's Aggressiveness at Ceylon

Post by cstunts » 16 Jul 2020 03:59

Actually the Allies had good suspicions (based on sigint, and that means codebreaking not just traffic analysis {No, check that; primarily traffic analysis, I now think}) that the Japanese were going to attack in the Indian Ocean well before mid-March, 1942. In the March 3-4 timeframe the British & American understood that IJN subs would be moving into the IO for ops there, probably based at Penang.
Station HYPO (Hawaii) did warn of a possible move towards Australia/NZ, but this was limited to First Air Fleet's CarDiv 2 (Hiryu & Soryu) only.
By 7 March the British detected msgs related to what they suspected was the Andaman Islands & preparations for establishing air activity (which is precisely what followed.)
By mid-March, as Prados acknowledges, "intelligence indicators fell into place with disturbing speed." More indications followed almost daily which showed Japanese movements generally heading west.
By the 21st the FECB knew that something was definitely afoot, and this included the warning of an attack on April 1, but there was mixed speculation re the target...Possible locations were India, Ceylon or Australia.
On the 26th Nimitz msg'd Somerville directly: "Indications remain strong that ORANGE intend offensive action Indian Ocean area." At this time, Station HYPE's intercepts & decrypts more or less coincided with similar work by British codebreakers, according to Prados. They understood that Kondo was the overall commander, and that he would be receiving extra cruiser & destroyer reinforcements.

US submarine performance in the opening phase of the PacWar was not hampered by poor intell--on the contrary--but was most definitely affected in a negative sense by pre-war doctrine, lack of aggressiveness, inadequate training, and the all-too-well-known torpedo issues. But, it should be understood that our sub force was a high priority recipient of sigint information, both in the period when we had codebreakers in the Philippines (Station CAST/the Corregidor Gang) and as soon as they were re-established in Australia (at Moorabbin/Melbourne, for example.)

At ground-level (or sea level), however, the IJN seems to have been remarkably paranoid about security and worried constantly about spying or concealed surveillance.

HTH

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