Indian Ocean raid

British Ceylon (Sri Lanka)

Ceylon (now Sri Lanka) is off the south-east of India between shipping routes from Singapore and Rangoon to the Red Sea and the Persian Gulf. There are natural harbours at Colombo on the south-western coast and Trincomalee on the north-eastern coast, a naval anchorage and base.^[2] Ceylon was a geographically important part of the British Empire and its system of trade, communication and military organisation. In the 1930s more shipping tonnage was handled in Ceylon than all the ports of India. Since the beginning of the Second World War, the colonial government had engaged in mass recruitment for local defence, overseas labouring and expanded food production.^[3] Tea and rubber production was emphasised and rubber output rose from 99,500 long tons (101,100 t) in 1941 to 105,500 long tons (107,200 t) in 1943.^[4] The 3,600 workers in civil engineering converted to the repair and refitting of ships and the manufacture of dummy aircraft, guns and radar installations.^[3]

When the Pacific War began on 7 December 1941, the Allied disasters in the Pacific, Malaya and the British débâcle at the Battle of Singapore in February 1942 made Colombo Harbour the basis for eastern trade and the centre for the assembly of Indian Ocean convoys. Colombo port was large enough for 45 ships but soon had 100 to 110 ships at once, causing much overcrowding.^[5] The fall of Singapore on 15 February 1942, the Allied defeat in the Dutch East Indies campaign (11 January – 9 March 1942) broke the British eastern defensive perimeter of the Bay of Bengal and the loss of the Andaman Islands on 23 March gave Japan control of the Andaman Sea, enabling ships to supply Japanese troops in the Burma Campaign.^[6] The Malacca Strait in the Netherlands East Indies was about 1,000 nmi (1,900 km; 1,200 mi) east of Trincomalee, making it Ceylon a useful base for attacks on Japanese ships sailing to Rangoon in Burma.^[2]

Ceylon was hastily garrisoned by Australian troops returning from North Africa and HMS Indomitable was used as a high-speed aircraft ferry, shuttling fighter aircraft to Ceylon.^[7] From September to December 1941, 710 troop reinforcements arrived on the island and from January to March 1942, another 2,612 arrived; during April and June, 2,112 more troops joined the garrison and 4,993 troops moved between the Far East and Ceylon from October 1941 to March 1942.^[8] The extent of the disasters that befell the British in early 1942, led in March to Admiral Sir Geoffrey Layton being transferred from the temporary command of the Eastern Fleet and installed as the Commander-in-Chief, Ceylon, after Admiral James Somerville took over the fleet. Layton was given authority over the military forces on the island and the civilian authorities of the governor, Sir Andrew Caldecott, "Do not ask permission to do things. Do them and report afterwards what you have done".^[9] Layton found the same complacency and inertia in Ceylon as he had experienced in Malaya,

...he takes complete charge of Ceylon and stands no nonsense from anyone.... He pulls all the Ministers legs... and they work for him all the harder.

Japanese preparations

A Japanese offensive into the Indian Ocean was postponed in March 1942 because the IJN was needed in the western Pacific against the United States and the Imperial Japanese Army (IJA) refused to allocate troops to invade Ceylon. The IJN planned a lesser effort, Operation C, a raid into the Indian Ocean in early April. C aimed to destroy the Eastern Fleet and disrupt British communications in the Bay of Bengal in support of the Japanese invasion of Burma.^[11] Admiral Isoroku Yamamoto issued the order to proceed with Operation C to the Southern Force of the IJN (Admiral Nobutake Kondō) on 9 March 1942. By 16 March, the force was to depart from Staring Bay, Celebes, on 26 March for an attack on Colombo on 5 April (C day) to catch the Eastern Fleet in port.^[12]

The Japanese force, commanded by Admiral Chūichi Nagumo, had five aircraft carriers, Akagi, Shōkaku and Zuikaku in Carrier Division 5 and Sōryū and Hiryū in Carrier Division 2. The carriers were protected by the four Kongo-class battleships and both Tone-class cruisers.^[13] Japanese intelligence on the Eastern Fleet was accurate but overestimated the air strength on Ceylon. The 19 March order was vague, a "considerable" portion of British naval and air forces in the Indian Ocean were "deployed in Ceylon area". The Japanese sent submarines to Colombo and Trincomalee to keep watch but they achieved little. The Maldive Islands were reconnoitred by submarine but failed to uncover that Gan (Port T) was a fleet fuelling base.^[14]

Malay Force

Cocanada

Vizagapatam

Calcutta

Akyab

Bay of Bengal location map

Concurrent with Operation C, the IJN dispatched Malay Force (Vice Admiral Jisaburō Ozawa) consisting of the aircraft carrier Ryūjō, six cruisers, a light cruiser and four destroyers.on a raid in the northern Bay of Bengal. The force departed from Mergui (now Myeik, Myanmar) on 1 April.^[15] The Eastern Fleet was far to the south, operating against Operation C and the British were incapable of defending the merchant ships in the Bay, having only a couple of Indian sloops and the Greek destroyer Ierax; merchant ships sailed in small groups and hugged the coast.^[16] On 5 April, at 16°N, 88°E, the force divided into North, Centre and South forces to search for targets south of False Point (20°20′N, 86°44′E) and Cocanada. On 5 April aircraft from Ryūjō sank a ship and Calcutta (now Kolkata) from where ships had been ordered to disperse on 31 March, cancelled sailings on 6 April.^[17]

On 6 April, aircraft from Ryūjō bombed the coastal towns of Cocanada and Vizagapatam causing minor damage and a panic that led to an exodus from both places. In three days, Malay Force managed to sink 20 merchant ships and damage three more of over 130,000 GRT in attacks by aircraft and ships.^[17] On the eastern side off the Bay, off Akyab (now Sittwe) in Burma at 20°7′N, 92°54′E, the Burma Coast Force was attacked by land-based aircraft and lost HMIS Indus a Grimsby-class sloop with ten men wounded. During the chaos caused by Operation C and the raid by Malay Force, the Japanese were able to get a convoy of troops and equipment into Rangoon.^[18] Another 32,000 GRT of shipping was sunk by Japanese submarines off the west coast of India during the month.^[19]

British preparations

The reinforcement of the Eastern Fleet depended on transfers from Britain and the Mediterranean. In late December 1941, a reassessment of the threat posed by Japan envisioned the Navy transferring the majority of the big ships to the Eastern Fleet. Matters were made urgent by the Attack on Pearl Harbor that sank much of the United States Pacific Fleet, that exposed the weak forces in Malaya to attack. Heavy units were freed by American reinforcements in the Atlantic. The pre-war rearmament was beginning to yield more big ships. The Mediterranean Fleet transferred far less reinforcements than expected due to its losses in 1941.^[20]

Somerville assumed command of an Eastern Fleet in March 1942 that was smaller than envisioned in December 1941. Somerville divided the fleet into a fast Force A comprising the aircraft carriers HMS Formidable and Indomitable, the modernised battleship HMS Warspite (as flagship) and the modern cruisers and destroyers. Force B was formed around the old carrier HMS Hermes and four un-modernised Revenge-class battleships; a few submarines were also available. The ships had not operated together before and ship and air crews were deficient in training.^[21]

The Far East Combined Bureau (FECB) intelligence assessment of the strength of the Japanese force was mistaken, identifying only two carriers in the Japanese force. FECB also believed the Japanese would sail from Staring Bay on 21 March and that C Day was 1 April. Somerville planned to evade the Japanese during the day and close for torpedo attacks at night with radar-equipped Fairey Albacore torpedo-bombers. Somerville had orders from the Admiralty, to protect the communications in the Indian Ocean and to keep the Eastern Fleet in being by avoiding risks but sailed to attack the Japanese force, having been convinced by the FECB that its assessment was accurate.^[22]

On 7 December 1941, the Ceylon air defences consisted of four obsolescent three-inch anti-aircraft guns at Trincomalee, with no fighters or radar. By 4 April, there were 67 Hawker Hurricanes and 44 Fairey Fulmar fighters, radar stations at Colombo and Trincomalee and 144 anti-aircraft guns. There were three RAF fighter squadrons, two at Colombo and one at Trincomalee, with 37–38 operational Hurricanes around Colombo on 5 April.^[23] Two squadrons of Fleet Air Arm (FAA) Fulmars had also arrived.^[24] Other squadrons increased from eight obsolete torpedo bombers, to seven Consolidated PBY Catalina flying boats, 14 Bristol Blenheim IV bombers, and 12 Fairey Swordfish torpedo bombers. On the eve of the battle, the air defences were part of 222 Group (Air Vice-Marshal John D'Albiac).^[25]

26 March − 3 April

The Japanese sailed from Staring-baai (Staring Bay) on 26 March as planned. Somerville sailed on 30 March, expecting an attack on 1 April and took the fleet to a patrol area 100 nmi (190 km; 120 mi) south of Ceylon. Ceylon air defences and forces went on alert, with land-based aerial reconnaissance concentrating on the south-east, where the Japanese were expected to approach for attacks on Colombo and Trincomalee.^[26] Late on 2 April, the Eastern Fleet retired toward Port T 600 nmi (1,100 km; 690 mi) south-west of Ceylon to fuel. Somerville detached several ships to resume their commitments; the heavy cruisers HMS Cornwall and Dorsetshire were sent to Colombo and Hermes to Trincomalee.^[27] The air defences stood down, except for Catalina patrols.^[28]

4 April

At about 16:00 on 4 April, PBY Catalina flying boat (AJ155/QL-A) from 413 Squadron, Royal Canadian Air Force (RCAF) flown by Squadron Leader Leonard Birchall spotted the Southern Force 360 mi (580 km) south-east of Ceylon on a course that would have entered the British fleet patrol area from the south.^[29] The Catalina transmitted the sighting but not the size of the force before being shot down. Somerville was refuelling at Port T; Force A sailed eastwards toward the Japanese upon receiving the sighting; Force B could not be ready until 5 April.^[30][24] Catalina FV-R from 205 Squadron took off at 17:45 to shadow the Japanese force, making its first report at 22:37 on 4 April and a final report at 06:15 on 5 April while 110 nmi (200 km; 130 mi) from Ceylon. FV-R was shot down about 90 minutes after the final report.^[29]

D'Albiac briefed his staff on an anticipated Japanese attack after dawn, 222 Group issued a warning and units went on alert at 04:00 on 5 April. Six Swordfish from 788 Naval Air Squadron (788 NAS) flew from China Bay, near Trincomalee, to Colombo, to be ready for an attack on the Japanese force.^[31] Layton ordered ships to disperse from harbour. Cornwall and Dorsetshire, that had just reached Colombo, had been sent back towards Force A late on 4 April. Hermes sailed from Trincomalee and was ordered to hide north-east of Ceylon.^[32] The Japanese did not reconnoitre their intended course on the afternoon of 4 April and a reconnaissance of Colombo harbour by cruiser floatplanes was cancelled.^[33] The Japanese intercepted a signal from Colombo asking QL-A to repeat its report, the Japanese had lost surprise.^[34]

5 April

Japanese intelligence on the morning of 5 April 1942 indicated that British carriers were absent and the Japanese morning air search was limited accordingly.^[35] At dawn, Japanese aircraft flew off to the south-west and north-west out to200 nmi (370 km; 230 mi) over the next few hours. A Fulmar from Force A at 08:00, spotted one of the Japanese aircraft at the extreme edge of the south-west search area at 08:55 about 140 nmi (260 km; 160 mi) ahead of Force A.^[36]

Shortly after 06:00 91 Japanese bombers and 36 fighters began taking off for the attack on Colombo.^[37] British early warning failed to detect the Japanese aircraft and British pilots had to scramble when the first Japanese aircraft appeared over them at 07:45. The defence of Ratmalana airfield by British fighters left the harbour wide open. The armed merchant cruiser HMS Hector, the Norwegian tanker Soli and the old destroyer HMS Tenedos were sunk; three other ships were damaged. The port was damaged but was not put out of action.^[24]

At Ratmalana airfield RAF Hurricanes and FAA Fulmars were caught taxying and taking off by Japanese dive-bombers and fighters.^[38] Twenty of the 41 British fighters that took off were shot down. At least one fighter was damaged and crashed on take-off and the six Swordfish of 788 NAS arrived and were shot down by the Zeros. The Japanese lost seven aircraft.^[39] Nagumo changed course to west-south-west at 08:30, unknowingly causing the opposing fleets to steam toward one another and recovered the aircraft from 09:45 to 10:30. The size of the attack on Colombo was Somerville's first evidence that the Japanese force had more than the two carriers expected. Somerville continued to steam toward the Japanese force at 18 kn (33 km/h; 21 mph). Radar-based fighter direction would allow Force A to avoid surprise attack by neutralising shadowing Japanese aircraft.^[40]

Cornwall and Dorsetshire

At 10:00, an aircraft from Tone searching to the south-west, spotted the two cruisers and began shadowing; the aircraft reported that the cruisers were heading south-west at 24 kn (44 km/h; 28 mph).^[40] The cruisers reported the shadowing aircraft but had no means to drive it off.^[41] Nagumo increased speed from 24 to 28 kn (44 to 52 km/h; 28 to 32 mph) on receiving the sighting. The Carrier Division 5 reserve was ordered to rearm with torpedoes, replacing the bombs intended for a second attack on Colombo. The rearming took too long and Carrier Division 2 attacked instead.^[42]

Sōryū and Hiryū began launching dive-bombers at 11:45. Radar on the Force A ships detected the attack on the cruisers at 13:44, putting the aircraft 34 nmi (63 km; 39 mi) to the north-east. Cornwall and Dorsetshire were sunk at 14:00 with the loss of 424 men.^[43] The Japanese did not find Force A after sinking the cruisers. Had the aircraft shadowing the cruisers flown another 50 nmi (93 km; 58 mi) along the cruisers' course before returning to Tone, it would have detected Force A. The Japanese aircraft began landing at 14:45.^[42]

5 April, afternoon

Somerville launched four Albacores from Indomitable at 14:00 to search an arc to the north-east out to 200 nmi (370 km; 230 mi). The south-easterly course of the Japanese force would have taken it through the centre of the arc. At 15:00 or 15:30, Nagumo changed course to the south-west. Carrier Division 2 did not immediately follow; it performed a series of kinking manoeuvres starting at 15:00 that initially took it north-west. Carrier Division 2 was spotted by the two northerly Albacores around 16:00. Zeros from Hiryū intercepted the Albacores, damaging one at 16:04 and the other was shot down at 16:28 without reporting. The two southern-most Albacores missed the Southern Force.^[44]

Somerville received the damaged Albacore's sighting report at 16:55 giving the position of Carrier Division 2 with reasonable accuracy, 125 nautical miles (232 km; 144 mi) away but nothing else. At 17:00 he received signals intelligence from Colombo reporting the Japanese course at 14:00 to be south-westerly, at 24 kn (44 km/h; 28 mph). Somerville ordered a course change to the south-west at 17:26, not knowing that Nagumo's main body was 120 nmi (220 km; 140 mi) away and that Carrier Division 2 was only 100 nmi (190 km; 120 mi) away. The course change meant that the British lost an opportunity to attack; had Force A continued on its easterly course, Carrier Division 2 would have passed across its front at 21:00 at a range of about 20 nmi (37 km; 23 mi).^[45]

There were two revisions to the 16:05 sighting, transmitted to Somerville at 18:00 and 18:17 respectively that differed significantly from each other and the original report. The final revision identified Carrier Division 2 but they were heading north-west 25 nmi (46 km; 29 mi) of the original sighting. The course heading conflicted with the first revision, that suggested a course toward the south-east. Late on 5 April, FECB decrypted a JN 25B message of Nagumo's planned movements on 6 April but this was no help as the transmission was garbled. Somerville ordered each of his carriers to prepare a squadron of torpedo-bombers for a night attack.^[46] Somerville declined to attack based on poor information and headed north-west in pursuit. A radar-equipped aircraft was launched to search a northern arc out to 200 nmi (370 km; 230 mi). Aircraft were sent later to search the easterly arc but it was too late to re-gain contact with the Japanese.^[47]

the Japanese missed an opportunity to find the British before night fell. Nagumo did not order a search for the British carriers at the appearance of carrier aircraft. Search aircraft might require homing signals from the carriers to return, that the British could also use. The Southern Force continued south-east at 20 kn (37 km/h; 23 mph) ignorant of Force A. Carrier Division 2 caught up at 22:00 180 nmi (330 km; 210 mi) due east of Force A.^[48] The Japanese circled wide to the south and then east ready to attack Trincomalee.^[41] The Japanese suspected the presence of British carriers and on the morning of 6 April sent aircraft on a comprehensive westwards search and still found nothing.^[49] Searches en route to Trincomalee were equally unsuccessful as the British carriers were far to the west.^[41]

6–8 April

By 6 April, FECB decrypts of Japanese wireless codes indicated the force contained four carriers and three battleships, beyond the capacity of the Eastern Fleet to engage without undue risk. The declining serviceability of the fighter force reinforced his caution but Somerville did not immediately withdraw or return to port; Force B rejoined early on 6 April. In the afternoon 1,122 survivors from Cornwall and Dorsetshire were rescued, while maintaining a look-out for the Japanese force with all-around air reconnaissance.^[50] Intelligence from Ceylon put the Japanese between Port T and Ceylon. Somerville cautiously arrived at Port T from the west at 11:00 on 8 April and refuelled. The Eastern Fleet had withdrawn and the Japanese were approaching Trincomalee from the east. Thesouthern Force was detected by a RAF Catalina at 15:17 on 8 April and the harbour at Trincomalee was cleared that night. Hermes, escorted by HMAS Vampire, was sent south along the coast.^[51]

9 April

The Japanese air search on the morning of 9 April was limited as British carriers were no longer expected.^[35] The Japanese strike group of 132 aircraft was detected at 07:06 by AMES 272 91 mi (146 km) from Trincomalee. The RAF and FAA scrambled 17 Hurricanes and six Fulmars in good time and a section of Hurricanes, already airborne on dawn patrol, attacked three Zeroes and shot down two. The China Bay airfield and the port were severely bombed and the monitor HMS Erebus was damaged.^[52] SS Sagaing (7,968 GRT) a merchant ship carrying aircraft and ammunition was set on fire and abandoned, with two men killed of 138 crew; eventually the hulk drifted into Malay Cove.^[53] Eight Hurricanes and a Fulmar were shot down and several unserviceable aircraft were destroyed on the ground; the Japanese lost four aircraft. At 07:16 another Catalina from 413 Squadron RCAF spotted the Japanese force and was shot down while reporting.^[54]

Around 10:25, nine un-escorted Blenheims from 11 Squadron attacked Nagumo's force and eluded the combat air patrol (CAP).^[55] Hiryū spotted the aircraft but failed to relay a warning to the other ships and the attack achieved surprise.^[56] The bombers attacked Akagi at 11,000 ft (3,400 m) and the bombs fell close to Hiryū but none hit.^[57][56] Four Blenheims were shot down after they had bombed and turned for home by Zeros of the standing patrol and another by Japanese aircraft returning from the attack on Hermes. A Zero was shot down near the carriers and another in the formation returning from Trincomalee.^[58] This was the first time a Japanese carrier force had faced a concerted air attack.^[56]

Hermes and Vampire were 65 nautical miles (120 km; 75 mi) away when Trincomalee was attacked. At 09:00 they reversed course.^[59] Shortly after the attack on Trincomalee ended, a reconnaissance aircraft from Haruna spotted the ships. Eighty Aichi D3A Val bombers, held in reserve on the Japanese carriers, began an attack at 10:35 and the ships were sunk off Batticaloa before noon.^[60] Hermes was hit by over forty 500 lb (230 kg) bombs and sank with the loss of 307 men; eight of the crew on Vampire were killed. The nearby hospital ship HMHS Vita was not attacked as it rescued 600 survivors. Aircraft from Sōryū attacked HMS Hollyhock, a Flower-class corvette that was escorting RFA Athelstone and sank the corvette with the loss of 53 men.^[61] The tanker MV British Sergeant and the cargo ship SS Norviken were also sunk. British Fulmars arrived from Trincomalee too late to help Hermes but shot down four Vals for the loss of two of the Fulmars. Nagumo disengaged after recovering the strike on Hermes.^[55]

Analysis

In 2017, Andrew Boyd wrote that an Admiralty study, "Future British Naval Strategy" (14 December 1941) formed part of a comprehensive review of policy for the Far East, now that Japan had joined the war. The review emphasised the containment of the Japanese expansion, avoiding the loss of Singapore and other strategically valuable areas necessary for military recovery and reconquest. For six months, at least, the Indian Ocean was vital to the British and the corollary was the protection of Ceylon, whose defences were exiguous. The security of the Indian Ocean was a naval matter and a considerable effort would be necessary, with support from the United States Navy limited to the Atlantic. The review recognised that the Far East and Middle East must be seen as a whole. The Indian Ocean was perhaps, at the start of 1942, the most important theatre of operations for the British and the US after the Battle of the Atlantic and impinged on the survival of the USSR.^[62]

Somerville might have called the Eastern Fleet a rabble but it contained a large proportion of the big ships of the navy. Boyd wrote that operations around Ceylon had been historically neglected, treated more as disasters for a navy that was incapable of challenging the superiority of the Imperial Japanese Navy and a strategic sideshow. Boyd called the operations "more interesting" than that.^[62] Somerville

...underestimated the risks he was running at least up to dusk on 5 April. He drew over-optimistic conclusions from the...intelligence, he grossly underestimated IJN air strength and he hazarded the fleet against his instructions from the chiefs of staff. Ceylon was not his finest hour.^[63]

Japanese air superiority made it difficult to scout, close and attack during the day and a radar-based night attack was risky. Careful positioning, luck and Japanese errors nearly produced the conditions for an attack on the night of 5/6 April. The Southern Force was within 125 nmi (232 km; 144 mi) but information on the Japanese position was missing. Even then, it required experienced air crews to find their targets at night using new tactics and radar sets with a range of 20 nmi (37 km; 23 mi).^[64] Boyd wrote that Somerville took too many chances, especially sailing on 30 March, yet had come close to a resounding victory.^[63] Had the Japanese had approached as expected from the south-east and the British failed to find them, the two forces would be about 100 nmi (190 km; 120 mi) apart at dawn. The British could have been detected by Japanese aerial reconnaissance and attacked by carrier aircraft all day. The Eastern Fleet would have been just as vulnerable had they been present when the Japanese arrived from the south-west.^[33]

The failure of the Japanese to appear as anticipated on 1–2 April, led Somerville mistakenly to believe that all of the intelligence on Operation C was flawed. He detached Cornwall, Dorsetshire and Hermes that were sunk in areas watched by Japanese aerial reconnaissance. Re-fuelling at Port T a few days later, rather than at Ceylon on 2 April, kept the British away from the Southern Force and perhaps averted disaster.^[65] The Japanese failed to find the bulk of the Eastern Fleet and the British overestimated the danger to Ceylon, because signals intelligence had suggested that the Japanese were preparing a deliberate advance across the Indian Ocean.^[66] The raid demonstrated that the RAF was too weak to defend Ceylon and that the navy was ill-prepared to meet a Japanese carrier force.^[67] By June, Ceylon had three RAF fighter squadrons (64 aircraft, plus 50 per cent reserves) three anti-shipping squadrons (including one of Beaufort torpedo bombers) also with 50 per cent reserves and much improved radar with the anti-aircraft defences manned by two Australian infantry brigades.^[68]

The Eastern Fleet withdrew to the port of Kilindini in the East Africa Protectorate (Kenya) temporarily to abandon the eastern Indian Ocean to Japan; from there it contested control of the central Indian Ocean.^[69] On 18 April, the Eastern Fleet was accorded the highest priority for reinforcement, including the transfer of most of the carriers from the Home Fleet and the Mediterranean Fleet, intended to return to Ceylon in September, having received Warspite, HMS Valiant, HMS Nelson and HMS Rodney. Force A, with its two aircraft carriers, went to Bombay and Somerville sent the force to the central Indian Ocean several times over the next six months, operating near Ceylon for about half the time.^[1] The invasion scare was short-lived, British intelligence detecting the movement of the Japanese carrier force eastwards in mid-April and its arrival in the Pacific in mid-May.^[70] The reinforcement of the Eastern Fleet stopped and it was reduced in size in late July. In September, British intelligence predicted Japan would go over to the defensive.^[68]

Boyd called Nagumo rigid and unimaginative, contributing to the escape of the Eastern Fleet. The manoeuvring of the force was mainly to facilitate the raids on Colombo and Trincomalee; that the British might be at sea was apparently not seriously considered. He failed to appreciate that the direction that Cornwall and Dorsetshire was sailing and the later appearance of British carrier aircraft, were related. Aerial reconnaissance to provide Nagumo with information about his front and flanks was inadequate. Assuming that there was nothing to be found outside of the few searches made was an error.^[71] The lack of air reconnaissance reflected IJN practice, air searches being based on expected threats. More aircraft were devoted to the morning search on 6 April, on suspicion that British carriers might be present. Later air searches were reduced, when the British carriers had not been found and there was little expectation of encountering them.^[72] It was difficult to rearm aircraft at short notice and the lack of radar allowed the Blenheims to evade the CAP and this happened again disastrously at the Battle of Midway (4–7 June 1942).^[71]

The Japanese did not exploit their victory as the British feared, their aircraft carriers needed maintenance and replenishment after months of operations and there was already difficulty in maintaining the strength of frontline air units.^[73] Japanese commanders felt that the losses inflicted on the British did not justify the cost to Japanese aircrew.^[74] In early May, the aircraft carriers fought the Battle of the Coral Sea in the south-west Pacific, followed in June by the Battle of Midway ended the threat of serious Japanese naval operations in the Indian Ocean.^[75] Later Japanese operations, were conducted by submarines and armed merchant cruisers, with some success. The Allies invaded Madagascar (5 May – 6 November 1942) to prevent the Japanese from establishing a base to attack shipping and Japanese submarines attacked the harbour at Diego-Suarez.^[76]

Casualties

The Japanese damaged port facilities, sank one carrier and two cruisers, destroyed a third of enemy ground-based fighters and nearly all of the ground-based anti-shipping aircraft. In April,the Japanese sank 27 merchant ships, totalling 112,312 GRT including those by the Malay Force raid further north in the Bay of Bengal, concurrent with Operation C. The Japanese lost 18 aircraft, six fighters, ten dive-bomber, two bombers and about 31 more damaged.^[66]

Japanese aircraft

Ships sunk, 5 April 1942

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British warships sunk or damaged^[79]

Ship	Flag	Class	Notes
Colombo harbour
HMS Hector	Royal Navy	Armed merchant cruiser	Damaged, settled on bottom
HMS Lucia	Royal Navy	submarine depot ship	Damaged
HMS Tenedos	Royal Navy	S-class destroyer	Sunk
At sea
HMS Cornwall	Royal Navy	County-class cruiser	Sunk
HMS Dorsetshire	Royal Navy	County-class cruiser	Sunk

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Merchant ships sunk or damaged, 5 April 1942^[79]

Ship	Flag	GRT	Notes
Colombo harbour
SS Benledi	Merchant Navy	5,943	Damaged
SS Clan Murdoch	Merchant Navy	5,960	Damaged
MV Soli	Norway	5,834	Damaged

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Ships sunk, 9 April 1942

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Allied warships sunk or damaged, 9 April 1942^[80]

Ship	Flag	Class	Notes
Trincomalee harbour
HMS Erebus	Royal Navy	Monitor	Damaged, 9† 22 wounded
HNLMS Sumatra	Royal Netherlands Navy	Java-class cruiser	Damaged
At sea
HMS Hermes	Royal Navy	Aircraft carrier	Sunk, 7°35′28.39″N, 82°5′55.09″E 307†
HMS Hollyhock	Royal Navy	Flower-class corvette	Sunk, 07°30′N, 81°57′E, 53†
HMAS Vampire	Royal Navy	V-class destroyer	Sunk, 8†
HMHS Vita	Royal Navy	Hospital ship	Rescued 600 survivors, undisturbed by Japanese aircraft

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Merchant ships sunk or damaged, 9 April 1942^[81]

Ship	Year	Flag	GRT	Notes
In harbour
SS Sagaing	1925	Merchant Navy	7,968	Damaged, beached, 2† 136 surv, scuttled 1943
At sea
RFA Athelstane	1918	Merchant Navy	5,571	Tanker, bombed, sunk, 07°30′N, 81°56′E, 0†
SS British Sergeant	1922	Merchant Navy	5,868	Tanker, bombed, sunk, 08°01′N, 81°38′E, 0† 59 surv.
MV Norviken	1925	Norway	2,924	Bombed, ship abandoned, 4† 42 surv

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Malaya Unit Striking Force

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Malaya Force (1–11 April 1942)^[82]

Ship	(English)	Flag	Class	Notes
Vice-Admiral Jisaburō Ozawa
4th Carrier Squadron
Ryūjō	Prancing Dragon	Imperial Japanese Navy	Light aircraft carrier
Mikuma	Mikuma River	Imperial Japanese Navy	Mogami-class cruiser
Mogami	Mogami River	Imperial Japanese Navy	Mogami-class cruiser
Suzuya	Suzuya River	Imperial Japanese Navy	Mogami-class cruiser
7th Cruiser Squadron
Chōkai	Mount Chōkai	Imperial Japanese Navy	Takao-class cruiser
Takao	Mount Takao	Imperial Japanese Navy	Takao-class cruiser
11th Destroyer Division (to 3–4 April)
Yura	Yura River	Imperial Japanese Navy	Nagara-class cruiser
Fubuki	Blizzard	Imperial Japanese Navy	Fubuki-class destroyer
Shirayuki	White Snow	Imperial Japanese Navy	Fubuki-class destroyer
Hatsuyuki	First Snow	Imperial Japanese Navy	Fubuki-class destroyer
Murakumo	Massed Clouds	Imperial Japanese Navy	Fubuki-class destroyer
20th Destroyer Division (from 3–4 April)
Amagiri	Fogged/Clouded Sky	Imperial Japanese Navy	Fubuki-class destroyer
Asagiri	Morning Fog	Imperial Japanese Navy	Fubuki-class destroyer
Shirakumo	White Cloud	Imperial Japanese Navy	Fubuki-class destroyer
Yūgiri	Evening Mist	Imperial Japanese Navy	Fubuki-class destroyer
Submarine Unit C
I-2	1926	Imperial Japanese Navy	Type J1 submarine
I-3	1926	Imperial Japanese Navy	Type J1 submarine
I-4	1929	Imperial Japanese Navy	Type J1 submarine
I-5	1932	Imperial Japanese Navy	Junsen I Mod (I-5 class)
I-6	1935	Imperial Japanese Navy	Junsen II (I-6 class)
I-7	1937	Imperial Japanese Navy	Junsen III (I-7 class)

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Guard Unit^[82]

Ship	(English)	Flag	Class	Notes
Guard Unit
Sendai	Blizzard	Imperial Japanese Navy	Sendai-class cruiser
Fubuki	Blizzard	Imperial Japanese Navy	Fubuki-class destroyer	11th Destroyer Division
Shirayuki	White Snow	Imperial Japanese Navy	Fubuki-class destroyer	11th Destroyer Division
Hatsuyuki	First Snow	Imperial Japanese Navy	Fubuki-class destroyer	11th Destroyer Division
Murakumo	Massed Clouds	Imperial Japanese Navy	Fubuki-class destroyer	11th Destroyer Division
Uranami	Shore Wave	Imperial Japanese Navy	Fubuki-class destroyer	11th Destroyer Division
Isonami	Shore Wave	Imperial Japanese Navy	Fubuki-class destroyer	11th Destroyer Division

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Replenishment ships

More information Ship, Year ...

Supply Unit^[78]

Ship	Year	Flag	Class	Notes
Supply Unit
MV Nishiei Maru	—	Imperial Japanese Navy	Tanker
Ayanami	Twilled Waves	Imperial Japanese Navy	Fubuki-class destroyer	Det. 4th Carrier Division
Shiokaze	Sea Breeze	Imperial Japanese Navy	Minekaze-class destroyer	Det. 4th Carrier Division
1st Supply Division
MV Shunkoku Maru	1940	Imperial Japanese Navy	Kawasaki-type oiler
MV Ken'yō Maru	1939	Imperial Japanese Navy	Kawasaki-type oiler
MV Nippon Maru	1936	Imperial Japanese Navy	Kawasaki-type oiler
MV Tōei Maru	1939	Imperial Japanese Navy	Kawasaki-type oiler
2nd Supply Division
MV Nichiro Maru		Imperial Japanese Navy	oiler
MV Tōei Maru No. 2	1939	Imperial Japanese Navy	Kawasaki-type oiler
MV Hoyo Maru	1939	Imperial Japanese Navy	Kawasaki-type oiler

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Malaya Force groups

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Malaya Force (1–11 April 1942)^[83]

Ship	(English)	Flag	Class	Notes
North Unit
Kumano	Kumano River	Imperial Japanese Navy	Mogami-class cruiser	7th Cruiser Division
Suzuya	Suzuya River	Imperial Japanese Navy	Mogami-class cruiser	7th Cruiser Division
Shirakumo	White Cloud	Imperial Japanese Navy	Fubuki-class destroyer	20th Destroyer Division
Centre Unit
Ryūjō	Prancing Dragon	Imperial Japanese Navy	Light aircraft carrier	4th Carrier Division
Chōkai	Mount Chōkai	Imperial Japanese Navy	Takao-class cruiser
Yura	Yura River	Imperial Japanese Navy	Nagara-class cruiser
Asagiri	Morning Fog	Imperial Japanese Navy	Fubuki-class destroyer	20th destroyer Division
Yūgiri	Evening Mist	Imperial Japanese Navy	Fubuki-class destroyer	20th destroyer Division
South Unit
Mikuma	Mikuma River	Imperial Japanese Navy	Mogami-class cruiser	7th Cruiser Division
Mogami	Mogami River	Imperial Japanese Navy	Mogami-class cruiser	7th Cruiser Division
Amagiri	Fogged/Clouded Sky	Imperial Japanese Navy	Fubuki-class destroyer	20th Destroyer Division

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Ships sunk by Malaya Force

More information Name, Year ...

Merchant ships attacked^[84]

Name	Year	Flag	GRT	Notes
SS Harpasa	1934	Merchant Navy	5,082	5 April 1942, carrier aircraft 19°19′N, 85°46′E, 11† 33 surv, sank
SS Dardanus	1923	Merchant Navy	7,726	6 April 1942, gunfire, carrier aircraft
SS Point Clear	1920	United States	4,839
SS Bienville	1921	United States	5,491	6 April 1942, carrier aircraft, 17°48′N, 84°09′W, 24† 17 surv, sank
SS Ganges	1930	Merchant Navy	6,245	6 April 1942, carrier aircraft, sunk, 15†
SS Sinkiang	1915	Merchant Navy	2,646	6 April 1942, carrier aircraft, 17°32′N, 82°50′E, no†
MV Banjoewangi	1939	Netherlands	1,279	6 April 1942, gunfire, sunk, 13†
MV Batavia	1939	Netherlands	1,279
SS Taksang	1935	Merchant Navy	3,471	6 April 1942, gunfire, 17°52′N, 83°40′E, sunk, 15† 107 surv
SS Selma City	1921	United States	5,686	7 April 1942, carrier aircraft, sunk, 0†
MV Van der Capellen	1942	Netherlands	2,073	8 April 1942, carrier aircraft, sunk, 0†
MV Anglo Canadian	1928	Merchant Navy	5,268
SS Gandara	1919	Merchant Navy	5,281	6 April 1942, gunfire, 16°03′N, 82°20′E, sunk, 13† 69 surv
MV Dagfred	1930	Norway	4,434	6 April 1942, gunfire, 16°15′N, 82°09′E, sunk, 0† 40 surv
SS Hermod	1925	Norway	1,515	6 April 1942, gunfire, Bay of Bengal, scuttled, 0†
MV Elsa	1928	Norway	5,381	6 April 1942, gunfire, 35 nmi E. of Cuttack. sunk, 1† 29 surv
SS Malda	1922	Merchant Navy	9,066	6 April 1942, gunfire, 19°45′N, 86°27′E, sunk, 25† 154 surv
SS Autolycus	1922	Merchant Navy	7,718	6 April 1942, gunfire, 19°40′N, 86°50′E, sunk, 18† 82 surv
SS Indora	1938	Merchant Navy	6,622	6 April 1942, gunfire, Bay of Bengal, sunk, 2† 81 surv
Exmoor	1919	United States	4,986	6 March 1942, gunfire, sunk
SS Silksworth	1922	Merchant Navy	4,921	6 April 1942, gunfire off Puri, sunk, 0† 57 surv
SS Shinkuang	1920	Merchant Navy	2,410	6 April 1942, gunfire, off Puri, 3†

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Army

More information Unit, Flag ...

Ceylon garrison, March 1942^[85]

Unit	Flag	Type	Notes
Ceylon Defence Force
Ceylon Light Infantry	British Army	Infantry
Ceylon Planters Rifle Corps	British Army	Infantry
Colombo Town Guard	British Army	Infantry
Ceylon Garrison Artillery	British Army	Artillery	6-inch naval, 9.2-inch naval
65th Heavy AA Regt	British Army	Anti-Aircraft	40 × 3.7-inch AA,, 4 × 3-inch 20 cwt AA
43rd Light AA Regt	British Army	Anti-Aircraft	69 × Bofors 40 mm AA from March 1942[86]
Indian Army
34th Indian Division	British Indian Army	Infantry
21st (East Africa) Infantry Brigade	British Army	Infantry	Attached to 34th Indian Division
Australian Army
6th Australian Division
16th Australian Brigade	Australian Army	Infantry
17th Australian Brigade	Australian Army	Infanry

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Royal Air Force, Fleet Air Arm

More information Flag, Type ...

222 Group RAF^[87]

	Flag	Type	Base	Notes
RAF
Colombo
11 Squadron	Royal Air Force	Bomber	Racecourse	14 Blenheim Mk IV
30 Squadron	Royal Air Force	Fighter	RAF Ratmalana	22 Hurricane Mk IIb, 8 shot down
258 Squadron	Royal Air Force	Fighter	Racecourse	9 Hurricane Mk IIb, 5 Mk Ib, 8 shot down
Galle
202 Squadron	Royal Air Force	Flying boat	RAF Koggala	1 Catalina
205 Squadron	Royal Air Force	Flying boat	RAF Koggala	Catalina FV-R
413 Squadron	Royal Canadian Air Force	Flying boat	RAF Koggala	3 Catalina
Netherlands Naval Aviation Service
Groep Vliegtuig-2	Marineluchtvaartdienst	Flying boat	RAF Koggala	(Aircraft Group-2 [GVT-2]) Catalina Y-64
Groep Vliegtuig-16	Marineluchtvaartdienst	Flying boat	RAF Koggala	(GVT-16) Catalinas Y-55, Y-56 and Y-57
Trincomalee
261 Squadron	Royal Air Force	Fighter	RAF China Bay	1 Hurricane Mk I, 17 Mk IIb
273 Squadron	Royal Air Force	Fighter	RAF China Bay	16 Fulmar Mk I, Mk II
788 Naval Air Squadron	Fleet Air Arm	Torpedo-bomber	RAF China Bay	6 Swordfish, Albacore, 6 Swordfish shot down
803 Naval Air Squadron	Fleet Air Arm	Carrier fighter	RAF China Bay	12 Fulmar Mk II
806 Naval Air Squadron	Fleet Air Arm	Carrier fighter	RAF China Bay	12 Fulmar Mk II
814 Naval Air Squadron	Fleet Air Arm	Torpedo-bomber	RAF China Bay	10 Swordfish ashore from HMS Hermes
HMS Indomitable	Fleet Air Arm	Fighter	RAF China Bay	2 Martlet ashore from Indomitable

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Eastern Fleet

More information Ship, Flag ...

Eastern Fleet^[88]

Ship	Flag	Class	Notes
Admiral James Somerville
Force A
HMS Formidable	Royal Navy	Illustrious-class aircraft carrier
HMS Indomitable	Royal Navy	Illustrious-class aircraft carrier
HMS Warspite	Royal Navy	Queen Elizabeth-class battleship	Flag
Heavy cruisers
HMS Cornwall	Royal Navy	County-class cruiser
HMS Dorsetshire	Royal Navy	County-class cruiser
Light cruisers
HMS Emerald	Royal Navy	Emerald-class cruiser
HMS Enterprise	Royal Navy	Emerald-class cruiser
Destroyers
HMS Foxhound	Royal Navy	F-class destroyer
HMS Hotspur	Royal Navy	H-class destroyer
HMS Napier	Royal Navy	N-class destroyer
HMAS Nestor	Royal Navy	N-class destroyer
HMS Paladin	Royal Navy	P-class destroyer
HMS Panther	Royal Navy	P-class destroyer
Vice-Admiral Algernon Willis
Force B
HMS Hermes	Royal Navy	aircraft carrier	12 Fairey Swordfish, 10 ashore, 2 u/s
HMS Ramillies	Royal Navy	Revenge-class battleship
HMS Resolution	Royal Navy	Revenge-class battleship
HMS Revenge	Royal Navy	Revenge-class battleship
HMS Royal Sovereign	Royal Navy	Revenge-class battleship
Light cruisers
HMS Caledon	Royal Navy	C-class cruiser
HMS Dragon	Royal Navy	Danae-class cruiser
Jacob van Heemskerck	Royal Netherlands Navy	Tromp-class cruiser
Destroyers
HMS Arrow	Royal Navy	A-class destroyer
HMS Decoy	Royal Navy	D-class destroyer
HMS Fortune	Royal Navy	F-class destroyer
HMS Griffin	Royal Navy	G-class destroyer
HNLMS Isaac Sweers	Royal Netherlands Navy	Gerard Callenburgh-class destroyer
HMAS Norman	Royal Navy	N-class destroyer
HMS Scout	Royal Navy	S-class destroyer
HMAS Vampire	Royal Navy	V-class destroyer

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Eastern Fleet aircraft

More information Type, Notes ...

 Fleet Air Arm Carrier squadrons^[89]

	Type	Notes
HMS Formidable
888 Naval Air Squadron	12 Martlet Mk II	Fighter
818 Naval Air Squadron	9 Fairey Albacore	Torpedo-bomber
820 Naval Air Squadron	12 Fairey Albacore	Torpedo-bomber
HMS Indomitable
800 Naval Air Squadron	12 Fairey Fulmar Mk II	Fighter
880 Naval Air Squadron	9 Sea Hurricane Mk Ib	Fighter
827 Naval Air Squadron	12 Fairey Albacore	Torpedo-bomber
831 Naval Air Squadron	12 Fairey Albacore	Torpedo-bomber
HMS Hermes
814 Naval Air Squadron	12 Fairey Swordfish Mk I	10 Swordfish torpedo-bombers ashore at RAF China Bay, 2 u/s

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