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.
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.