Indian Ocean raid

The Indian Ocean raid (Operation C) the Third Mobile Operation in the Indian Ocean and the Battle of Ceylon in Japanese, was a sortie of the Imperial Japanese Navy (IJN) from 31 March to 10 April 1942. Japanese aircraft carriers (Admiral Chūichi Nagumo) struck Allied shipping, naval bases and airfields around British Ceylon but failed to find most of the Eastern Fleet. The British were forewarned by intelligence and the fleet sailed before the raid; its attempt to surprise the Japanese was frustrated by poor tactical intelligence.

Following Operation C, the British expected a Japanese offensive in the Indian Ocean. The main base of the Eastern Fleet was moved to East Africa and Ceylon was reinforced. Somerville kept his fast carrier division, Force A, "in Indian waters, to be ready to deal with any attempt by the enemy to command those waters with light forces only". The Japanese had no plans to follow up their success and within the year, operations in the Pacific made it impossible to do so.

Background

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. 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. Tea and rubber production was emphasised and rubber output rose from in 1941 to in 1943. 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.

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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. 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. The Malacca Strait in the Netherlands East Indies was about east of Trincomalee, making Ceylon a useful base for attacks on Japanese ships sailing to Rangoon in Burma.

Ceylon was hastily garrisoned by Australian troops returning from North Africa and was used as a high-speed aircraft ferry, shuttling fighter aircraft to Ceylon. 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. 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". Layton found the same complacency and inertia in Ceylon as he had experienced in Malaya,

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, also named the "Third Mobile Operation in the Indian Ocean", a raid into the Indian Ocean in early April. Operation C aimed to destroy the Eastern Fleet and disrupt British communications in the Bay of Bengal, in support of the Japanese invasion of Burma. Admiral Isoroku Yamamoto issued the order to proceed with Operation C to the 2nd Fleet and the Southern Force () of the IJN (Admiral Nobutake Kondō) on 9 March 1942. By 16 March, the plan was for the (1st Air Fleet) 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.

The Japanese force, commanded by Admiral Chūichi Nagumo, had five aircraft carriers, , and in Carrier Division 5 and and in Carrier Division 2. The carriers were protected by the four s and both s. 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.

2nd Submarine Squadron

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In Southern Force order 139, issued on 20 March, the commander of the 2nd Submarine Squadron, Rear-Admiral Hisashi Ichioka, required that two days before the raid on Ceylon, the submarine was to send its Watanabe E9W seaplane (Slim to the Allies) on reconnaissance over Colombo and Trincomalee and on the day of the carrier attack reconnaissance and weather data were to be gathered by and . and were to attack Allied ships as the fled from Ceylon after the carrier raid. was sent back to Yokosuka for repairs to its starboard diesel and was to patrol off Cape Comorin (now Kanyakumari), the southern tip of India.

British preparations

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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.

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 and Indomitable, the modernised battleship (as flagship) and the modern cruisers and destroyers. Force B was formed around the old carrier and four un-modernised s; a few submarines were also available. The ships had not operated together before and ship and air crews were deficient in training.

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.

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. Two squadrons of Fleet Air Arm (FAA) Fulmars had also arrived. 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).

Raid

26 March − 3 April

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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 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. Late on 2 April, the Eastern Fleet retired toward Port T south-west of Ceylon to fuel. Somerville detached several ships to resume their commitments; the heavy cruisers and were sent to Colombo and Hermes to Trincomalee. The air defences stood down, except for Catalina patrols.

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 south-east of Ceylon on a course that would have entered the British fleet patrol area from the south. 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. 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 from Ceylon. FV-R was shot down about 90 minutes after the final report.

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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. 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. 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. The Japanese intercepted a signal from Colombo asking QL-A to repeat its report, the Japanese had lost surprise.

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. At dawn, Japanese aircraft flew off to the south-west and north-west out to 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 ahead of Force A. Shortly after 06:00 91 Japanese bombers and 36 fighters began taking off for the attack on Colombo. 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. , an armed merchant cruiser, the Norwegian tanker and the old destroyer were sunk; three other ships were damaged. The port was damaged but was not put out of action. At Ratmalana airfield, RAF Hurricanes and FAA Fulmars were caught taxiing and taking off by Japanese dive-bombers and fighters. Twenty of the 41 British fighters that took off were shot down. At least one fighter was damaged and crashed on take-off. The six Swordfish aircraft of 788 NAS arrived overhead, quickly to be shot down by the Japanese fighters. The Japanese lost seven aircraft.

Cornwall and Dorsetshire

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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 . Radar-based fighter direction would allow Force A to avoid surprise attack by neutralising shadowing Japanese aircraft. 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 . Cornwall was heading for Colombo to resume its refit and Dorsetshire to escort a troop convoy. The cruisers reported the shadowing aircraft but had no means to drive it off.

Nagumo had increased speed from 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. 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 to the north-east. Cornwall and Dorsetshire were sunk at 14:00 with the loss of 424 men. The Japanese did not find Force A after sinking the cruisers. Had the aircraft shadowing the cruisers flown another along the cruisers' course before returning to Tone, it would have detected Force A. The Japanese aircraft began landing at 14:45.

5 April, afternoon

Somerville launched four Albacores from Indomitable at 14:00 to search an arc to the north-east out to . 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.

Somerville received the damaged Albacore's sighting report at 16:55 giving the position of Carrier Division 2 with reasonable accuracy, 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 . Somerville ordered a course change to the south-west at 17:26, not knowing that Nagumo's main body was away and that Carrier Division 2 was only 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 .

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 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. 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 . Aircraft were sent later to search the easterly arc but it was too late to re-gain contact with the Japanese.

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 ignorant of Force A. Carrier Division 2 caught up at 22:00 due east of Force A. The Japanese circled wide to the south and then east ready to attack Trincomalee. 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. Searches en route to Trincomalee were equally unsuccessful as the British carriers were far to the west.

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. 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. The Southern Force was detected by a RAF Catalina at 15:17 on 8 April and Vice-Admiral Geoffrey Arbuthnot the Commander-in-Chief, East Indies Station ordered that ships be dispersed from the harbour at Trincomalee that night. Hermes, escorted by , was sent south along the coast.

9 April

Trincomalee

The danger of an attack on Trincomalee harbour like that on Colombo led to the port beingemptied of many ships. Hermes and the Australian destroyer Vampire, the corvette Hollyhock, the minelayer Teviot Bank and several auxiliaries were ordered southwards along the coast, to be a minimum of from port by dawn on 9 April. The monitor that carried Type 285 radar and six 3-inch anti-aircraft guns had been sent to Trincomalee during March for anti-aircraft protection and the Netherlands Great War-vintage cruiser remained in port. Nine merchant ships of 3,000 GRT also remained, with nine small naval vessels. At dawn the AMES 272 at Elizabeth Point, north of the harbour, received indications of aircraft out to sea, seaplanes had been sent from the Japanese fleet from 05:00 and 06:00 on reconnaissance towards the harbour and the coast on either side. A Catalina from 413 Squadron RCAF had set off from Koggala at 02:56 and between 07:08 and 07:16 the Catalina spotted the Japanese force about east of Trincomalee. The aircraft was shot down by Zeros before a sighting report could be completed; it was the third Catalina lost since 4 April.

The Japanese air search on the morning of 9 April was limited as British carriers were no longer expected. The 91 Kate torpedo-bombers, armed with bombs, escorted by 41 Zeros, was detected at 07:06 by AMES 272 out from Trincomalee. The RAF and FAA scrambled 17 Hurricanes, most being Mk IIs and six Fulmars in good time and a section of three Hurricanes, already airborne on dawn patrol, attacked Zeros about out to sea and shot down three for the loss of a Hurricane. The China Bay airfield and the port were severely bombed and the monitor Erebus was damaged. (7,968 GRT) a merchant ship carrying aircraft as deck cargo and ammunition was set on fire and abandoned, with two men killed of the 138 crew, the hulk drifting into Malay Cove. Eight Hurricanes and a Fulmar were shot down and several unserviceable aircraft were destroyed on the ground; the Japanese lost three Zeros and a Kate.

At sea

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|+Efficiency of 9 April attacks on ships at sea

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! scope="col" width="120px"|Ship

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|align="right"|45

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|align="right"|37

|align="left"|2, Akagi, 11, Hiryū, 14, Zuikaku, 18, Shōkaku

|align="right"|16

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|align="right"|16

|align="left"|12 Akagi, 4 Hiryū

|align="right"|6

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|align="right"|1

|align="left"|From Sōryū

|align="right"|6

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|align="right"|6

|align="left"|3 Akagi, 3 Hiryū

|align="right"|6

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|align="right"|5

|align="left"|From Sōryū

|align="right"|6

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|align="right"|5

|align="left"|From Sōryū

|align="right"|85

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|align="right"|70

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Around 10:25, nine un-escorted Blenheims from 11 Squadron attacked Nagumo's force and eluded the combat air patrol (CAP). Hiryū spotted the aircraft but failed to relay a warning to the other ships and the attack achieved surprise. The bombers attacked Akagi at and the bombs fell close to Hiryū but none hit. After they had bombed and turned for home, four Blenheims were shot down 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. This was the first time a Japanese carrier force had faced a concerted air attack.

Hermes and Vampire were away when Trincomalee was attacked. At 09:00 they reversed course and shortly after the attack on Trincomalee ended, a reconnaissance aircraft from 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. Hermes was hit by over forty bombs and sank with the loss of 307 men; eight of the crew on Vampire were killed when it was bombed and sank. The nearby hospital ship was not attacked as it rescued 595 survivors. Aircraft from Sōryū attacked , a that was escorting the tanker, , sank the corvette with the loss of 53 men and the tanker. The tanker and the cargo ship were also sunk. British Fulmars arrived from Trincomalee too late to help Hermes but shot down four Vals for the loss of two Fulmars.

Japanese withdrawal

By 13:25 the Japanese aircraft had landed apart from a standing patrol of Zeros over the fleet and Nagumo ordered the ships to turn east. At 19:30 the fleet changed course to the north-east for the Andaman Islands. Nagumo sent signals to the Combined Fleet reporting the sinking of Hermes and the other vessels, claiming a 77.6 per cent success rate for the dive-bombers during the day. One Japanese pilot described the sinking of the British ships as similar to bombing a target ship only easier. Later Japanese commentators thought that the success was a consequence of the Japanese naval aviators being the best in the world. During the raid, the 1st Air Fleet () suffered the loss of 17 aircraft, ten Vals, six Zeros and a Kate; 31 men were killed and two men severely wounded. On 10 April the fleet turned eastwards with standing patrols of Zeros keeping watch for submarines and reconnaissance aircraft. On the night of 11/12 April the fleet passed south of the Andaman Islands and turned for the Strait of Malacca. Soryū kept relays of four Kates and then four Vals airborne on patrol until 18:00. The ships passed Singapore on 13 April and the 5th Carrier Squadron detached for the South Pacific. On 22 April the remainder of the fleet began to enter ports in Japan.

Associated operations

Malay Force

Concurrent with Operation C, the IJN dispatched Malay Force (Vice Admiral Jisaburō Ozawa) consisting of the aircraft carrier , 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. 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 for protection; merchant ships sailed in small groups and hugged the coast.

On 5 April, at 16°N, 88°E, Malay Force divided into North, Centre and South forces to search for targets south of False Point (20°20′N, 86°44′E) and Cocanada (16°57′N, 82°15′E). 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. A day later, 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 in attacks by aircraft and ships.

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 a with ten men wounded. In the chaos caused by Operation C and the raid by Malay Force, the Japanese were able to slip a convoy of troops and equipment into Rangoon.

2nd Submarine Squadron

Of the seven ocean-going boats of the Japanese 2nd Submarine Squadron (Rear-Admiral Hisashi Ichioka) due to search for merchant ships and report on the Eastern Fleet, only five were operational when it began. had engine trouble and return to Japan for repairs. went aground in the entrance to Kendari in the Celebes (now Sulawesi) on 28 February and the other boats and it was still aground when the operation began, only joining in the operation on 25 March for a short and uneventful patrol around Ceylon. (Ichioka) was sent to reconnoitre the Ceylonese ports of Colombo and Trincomalee 48 hours before the first air raid but I-7 met difficulties. On 1 April a flying-boat attacked during the night when the submarine was to the south-east of the island. British patrols caused a seaplane reconnaissance planned for the next day to be cancelled. On 3 April, the submarine attacked the British merchant ship Glenshiel and sank it with two torpedoes and bombardment from the deck gun.

, with the commander of the 7th Submarine Division aboard, set off from Penang on 28 March for Colombo to study British ship movements and make weather forecasts. On 3 April the captain reported that there was difficulty in getting close to Colombo but by 5 April it had closed to and transmitted tow weather reports. On the morning of 7 April I-3 was to the west of Colombo, found seven freighters and fired four torpedoes at three ships and fired 39 shells from the deck gun and claimed to have damaged British Elmdale with the gun.

On 8 April, J-3 sank the British ship Fultala (5,051 GRT) with a torpedo west of Colombo. On 28 March departed Penang for Trincomalee, reaching its destination on 3 April, to report on British ship movements and the weather; during the Japanese raid of 9 April, I-2 saw several British ships being sunk. J-3 began its return journey on 10 April to Singapore having failed to find any targets. sailed from Penang to observe the Eight Degree Channel at the north end of the Maldives and on 6 April sank the US freighter Washingtonian (6,617 GRT) by torpedo.

began its patrol on 26 March against shipping off Bombay (now Mumbai) on the north-west coast of India and on 31 March, claimed a merchantman east of the Eight Degree Channel. On 2 April it sank the British Clan Ross (5,897 GRT) off Bombay with three torpedoes. On 7 April it sank British Bahadur (5,424 GRT) but took seven torpedoes and eight shells from the deck gun. After the 9 April raid on Trincomalee Ichioka gave orders for the squadron return to Singapore, the boats arriving from 15 to 17 April. The six submarines sank six merchant ships (5 certain) and four motor sailing ships. British records list five ships of 32,404 GRT, a disappointing tally given the number of ships in the region and the squadron had not spotted any ships of the Eastern Fleet. After the operation, the Japanese thought that dispersing the submarines was a mistake and that they would have been more effective if they had all operated off Colombo.

Aftermath

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.

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. Somerville

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 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 . Boyd wrote that Somerville took too many chances, especially sailing on 30 March, yet had come close to a resounding victory. Had the Japanese had approached as expected from the south-east and the British failed to find them, the two forces would be about 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.

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. 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. 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. 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.

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. 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, , and . 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. 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. 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.

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. 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. 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).

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 front line air units. Japanese commanders felt that the losses inflicted on the British did not justify the cost to Japanese aircrew. 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. 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.

Casualties

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|+Losses in Indian Ocean operations 2–9 April

! British

! Japanese

|Personnel||align="right"| 1,028 ||align="right"| 32

|Navy ships||align="right"| 7 ||align="right"| 0

|Merchant ships||align="right"| 29 ||align="right"| 0

|Aircraft||align="right"| 54 ||align="right"| 18

The Japanese damaged port facilities, sank the aircraft carrier Hermes, the cruisers Cornwall and Dorsetshire destroyed a third of the British 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 and by submarines on the west coast of India, concurrent with Operation C. The Japanese lost 17 aircraft, six Zeros, ten Vals and a Kate, with 31 damaged.

Japanese order of battle

Southern Force

{|class="wikitable sortable"

|+Southern Force

! scope="col" width="40px" |Ship

! scope="col" width="120px"|(English)

! scope="col" width="160px"|Flag

! scope="col" width="160px"|Class

! Notes

! colspan="5" |Vice-Admiral Chūichi Nagumo, C-in-C 1st Air Fleet ()

! colspan="5" |Striking Force ()

! colspan="5" |1st Carrier Squadron

|align="left"|

|align="left"|Red Castle

|align="left"|

! colspan="5" |2nd Carrier Squadron

|align="left"|

|align="left"|Blue [or Green] Dragon

|align="left"|

|align="left"|aircraft carrier

|align="left"|

|align="left"|Flying Dragon

|align="left"|

|align="left"|aircraft carrier

|align="left"|

! colspan="5" |5th Carrier Squadron (reserve)

|align="left"|

|align="left"|Soaring Crane

|align="left"|

|align="left"|Auspicious Crane

|align="left"|

Support Force

{|class="wikitable sortable"

|+Support Force ()

! scope="col" width="40px" |Ship

! scope="col" width="120px"|(English)

! scope="col" width="160px"|Flag

! scope="col" width="160px"|Class

! Notes

! colspan="5"|3rd Battleship Squadron

! colspan="5"|1st Section

|align="left"|

|align="left"|Mount Hiei

|align="left"|

|align="left"|3 Dave seaplanes

|align="left"|

|align="left"|Mount Kirishima

|align="left"|

|align="left"|3 Dave seaplanes

! colspan="5"|2nd Section

|align="left"|

|align="left"|Mount Haruna

|align="left"|

|align="left"|3 Dave seaplanes

|align="left"|

|align="left"|Mount Kongō

|align="left"|

|align="left"|3 Dave seaplanes

! colspan="5"|8th Cruiser Squadron

|align="left"|

|align="left"|Tone River

|align="left"|

|align="left"|1 Alf, 1 Jake, 3 Dave seaplanes

|align="left"|

|align="left"|Chikuma River

|align="left"|

|align="left"|1 Alf, 1 Jake, 3 Dave seaplanes

Kidō Butai cover force

{|class="wikitable sortable"

! scope="col" width="40px" |Ship

! scope="col" width="120px"|(English)

! scope="col" width="160px"|Flag

! scope="col" width="160px"|Class

! Notes

! colspan="5"|1st Torpedo Squadron

|align="left"|

|align="left"|Abukuma River

|align="left"|

|align="left"|1 Alf seaplane

! colspan="5"|4th Destroyer Division (2nd Section)

|align="left"|

|align="left"|Clover Wind

|align="left"|

|align="left"|Dancing Wind

|align="left"|

! colspan="5"|17th Destroyer Division

|align="left"|

|align="left"|Beach Wind

|align="left"|

|align="left"|Wind on the Beach

|align="left"|

|align="left"|Valley Wind

|align="left"|

|align="left"|Wind on the Sea

|align="left"|

! colspan="5"|18th Destroyer Division

|align="left"|

|align="left"|Hailstone

|align="left"|

|align="left"|Heat Haze

|align="left"|

|align="left"|Haze

|align="left"|

|align="left"|Phosphorescent Light

|align="left"|

|align="left"|Autumn Clouds

|align="left"|

|align="left"|det. 5th Carrier Division

Japanese carrier aircraft

{|class="wikitable sortable"

|+1st Air Fleet

! scope="col" width="50px" |Fighter

! scope="col" width="100px"|Dive bomber

! scope="col" width="140px"|Torpedo bomber

! Notes

! colspan="4" |Air attack Group

! colspan="4" |

|align="left"|19 Zero

|align="left"|17 Aichi D3A (Val)

|align="left"|18 Nakajima B5N (Kate)

|align="left"|54 aircraft, not all used on raid

! colspan="4" |

|align="left"|20 Zero

|align="left"|18 Aichi D3A (Val)

|align="left"|18 Nakajima B5N (Kate)

|align="left"|56 aircraft, not all used on raid

! colspan="4" |

|align="left"|18 Zero

|align="left"|18 Aichi D3A (Val)

|align="left"|18 Nakajima B5N (Kate)

|align="left"|54 aircraft, not all used on raid

! colspan="4" |Reserve

! colspan="4" |

|align="left"|18 Zero

|align="left"|19 Aichi D3A (Val)

|align="left"|19 Nakajima B5N (Kate)

|align="left"|56 aircraft, not used on raid

! colspan="4" |

|align="left"|18 Zero

|align="left"|19 Aichi D3A (Val)

|align="left"|18 Nakajima B5N (Kate)

|align=", not all used on raid"|55 aircraft, not used on raid

! colspan="4" |Totals

|align="left"| 93 Zero

|align="left"| 91 Aichi D3A (Val)

|align="left"| 91 Nakajima B5N (Kate)

|align="right"| 275, 111 reserves

Supply Force ()

{|class="wikitable sortable"

|+Supply Unit

! scope="col" width="100px" |Ship

! scope="col" width="20px"|Year

! scope="col" width="160px"|Flag

! scope="col" width="100px"|Class

! Notes

! colspan="5"|1st Supply Division

|align="left"|

|align="left"|1940

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

|align="left"|1939

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

|align="left"|1936

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

|align="left"|1939

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

|align="left"|1939

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

|align="left"|1934

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

! colspan="5"|2nd Supply Division

|align="left"|

|align="left"|Oiler

|align="left"|

|align="left"|1939

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

|align="left"|1939

|align="left"|

|align="left"|Kawasaki-type oiler

|align="left"|

Submarine Unit C

{|class="wikitable sortable"

|+Submarine reconnaissance

! scope="col" width="20px" |Boat

! scope="col" width="20px"|Year

! scope="col" width="160px"|Flag

! scope="col" width="120px"|Class

! Notes

! colspan="5" |2nd Submarine Division

|align="left"|

|align="left"|1924

|align="left"|

|align="left"|Type J1 submarine

|align="left"|To Yokosuka for engine repairs

|align="left"|

|align="left"|1926

|align="left"|

|align="left"|Type J1 submarine

|align="left"|

|align="left"|1926

|align="left"|

|align="left"|Type J1 submarine

|align="left"|

|align="left"|1929

|align="left"|

|align="left"|Type J1 submarine

|align="left"|

|align="left"|1932

|align="left"|

|align="left"|Junsen I Mod (I-5 class)

|align="left"|

|align="left"|1935

|align="left"|

|align="left"|Junsen II (I-6 class)

|align="left"|

|align="left"|1937

|align="left"|

|align="left"|Junsen III (I-7 class)

|align="left"|

Ships sunk, 5 April 1942

{|class="wikitable sortable"

|+British warships sunk or damaged

! scope="col" width="80px"|Ship

! scope="col" width="80px"|Flag

! scope="col" width="120px"|Class

! Notes

! colspan="4" |Colombo harbour

|align="left"|

|align="left"|Armed merchant cruiser

|align="left"|Damaged, settled on bottom

|align="left"|

|align="left"|submarine depot ship

|align="left"|Damaged

|align="left"|

|align="left"|S-class destroyer

|align="left"|Sunk

! colspan="4" |At sea

|align="left"|

|align="left"|Sunk

|align="left"|

|align="left"|Sunk

{|class="wikitable sortable"

|+Merchant ships sunk or damaged, 5 April 1942

! scope="col" width="100px"|Ship

! scope="col" width="120px"|Flag

! scope="col" width="20px"|GRT

! Notes

! colspan="4" |Colombo harbour

|align="left"|

|align="left"|5,943

|align="left"|Damaged

|align="left"|

|align="left"|5,960

|align="left"|Damaged

|align="left"|

|align="left"|5,834

|align="left"|Damaged

Air raids, 9 April 1942

Warships

{|class="wikitable sortable"

|+Sunk or damaged

! scope="col" width="80px"|Ship

! scope="col" width="150px"|Flag

! scope="col" width="110px"|Class

! Notes

! colspan="5" |Trincomalee harbour

|align="left"|

|align="left"|Monitor

|align="left"|Damaged, 9† 22 wounded

|align="left"|

|align="left"|Damaged

! colspan="5" |At sea

|align="left"|

|align="left"|Aircraft carrier

|align="left"|Sunk, 7°35′28.39″N, 82°5′55.09″E 307†

|align="left"|

|align="left"|Sunk, 07°30′N, 81°57′E, 53†

|align="left"|

|align="left"|V-class destroyer

|align="left"|Sunk, 8†

|align="left"|

|align="left"|Hospital ship

|align="left"|Rescued 600 survivors, undisturbed by Japanese aircraft

Merchant ships

{|class="wikitable sortable"

|+Sunk or damaged

! scope="col" width="100px"|Ship

! scope="col" width="20px"|Year

! scope="col" width="120px"|Flag

! scope="col" width="20px"|GRT

! Notes

! colspan="5" |In harbour

|align="left"|

|align="left"|1925

|align="left"|

|align="left"|7,968

|align="left"|Damaged, beached, 2† 136 surv, scuttled 1943

! colspan="5" |At sea

|align="left"|

|align="left"|1918

|align="left"|

|align="left"|5,571

|align="left"|Tanker, bombed, sunk, 07°30′N, 81°56′E, 0†

|align="left"|

|align="left"|1922

|align="left"|

|align="left"|5,868

|align="left"|Tanker, bombed, sunk, 08°01′N, 81°38′E, 0† 59 surv.

|align="left"|

|align="left"|1925

|align="left"|

|align="left"|2,924

|align="left"|Bombed, ship abandoned, 4† 42 surv

Malaya Unit Striking Force

{|class="wikitable sortable"

|+Malaya Force (1–11 April 1942)

! scope="col" width="40px" |Ship

! scope="col" width="120px"|(English)

! scope="col" width="160px"|Flag

! scope="col" width="140px"|Class

! Notes

! colspan="5" |Vice-Admiral Jisaburō Ozawa

! colspan="5" |4th Carrier Squadron

|align="left"|

|align="left"|Prancing Dragon

|align="left"|

|align="left"|Light aircraft carrier

|align="left"|

|align="left"|Mikuma River

|align="left"|

|align="left"|Mogami River

|align="left"|

|align="left"|Suzuya River

|align="left"|

! colspan="5" |7th Cruiser Squadron

|align="left"|

|align="left"|Mount Chōkai

|align="left"|

|align="left"|Mount Takao

|align="left"|

! colspan="5" |11th Destroyer Division (to 3–4 April)

|align="left"|

|align="left"|Yura River

|align="left"|

|align="left"|Blizzard

|align="left"|

|align="left"|White Snow

|align="left"|

|align="left"|First Snow

|align="left"|

|align="left"|Massed Clouds

|align="left"|

! colspan="5" |20th Destroyer Division (from 3–4 April)

|align="left"|

|align="left"|Fogged/Clouded Sky

|align="left"|

|align="left"|Morning Fog

|align="left"|

|align="left"|Tide Wind

|align="left"|

|align="left"|White Cloud

|align="left"|

Malaya Force groups

{|class="wikitable sortable"

|+Malaya Force (1–11 April 1942)

! scope="col" width="50px" |Ship

! scope="col" width="90px"|(English)

! scope="col" width="160px"|Flag

! scope="col" width="120px"|Class

! Notes

! colspan="5" |Northern Force

|align="left"|

|align="left"|Kumano River

|align="left"|

|align="left"|7th Cruiser Division

|align="left"|

|align="left"|Suzuya River

|align="left"|

|align="left"|7th Cruiser Division

|align="left"|

|align="left"|White Cloud

|align="left"|

|align="left"|20th Destroyer Division

! colspan="5" |Central Force

|align="left"|

|align="left"|Prancing Dragon

|align="left"|

|align="left"|Light aircraft carrier

|align="left"|4th Carrier Division

|align="left"|

|align="left"|Mount Chōkai

|align="left"|

|align="left"|Yura River

|align="left"|

|align="left"|Morning Fog

|align="left"|

|align="left"|20th Destroyer Division

|align="left"|

|align="left"|Evening Mist

|align="left"|

|align="left"|20th Destroyer Division

! colspan="5" |Southern Force

|align="left"|

|align="left"|Mikuma River

|align="left"|

|align="left"|7th Cruiser Division

|align="left"|

|align="left"|Mogami River

|align="left"|

|align="left"|7th Cruiser Division

|align="left"|

|align="left"|Clouded Sky

|align="left"|

|align="left"|20th Destroyer Division

Replenishment Unit

{|class="wikitable sortable"

|+Supply Unit

! scope="col" width="100px" |Ship

! scope="col" width="80px"|(English)

! scope="col" width="160px"|Flag

! scope="col" width="150px"|Class

! Notes

! colspan="5" |Transport Force ()

|align="left"|

|align="left"| —

|align="left"|

|align="left"|Tanker

|align="left"|

|align="left"|Twilled Waves

|align="left"|

|align="left"|Det. 4th Carrier Division

|align="left"|

|align="left"|Sea Breeze

|align="left"|

|align="left"|Det. 4th Carrier Division

Guard Unit

{|class="wikitable sortable"

|+Guard Unit

! scope="col" width="40px" |Ship

! scope="col" width="120px"|(English)

! scope="col" width="160px"|Flag

! scope="col" width="120px"|Class

! Notes

! colspan="5" |Cover Force ()

|align="left"|

|align="left"|Blizzard

|align="left"|

|align="left"|Flag, 3rd Torpedo Squadron

|align="left"|

|align="left"|Blizzard

|align="left"|

|align="left"|21st Destroyer Division, 3rd Torpedo Squadron

|align="left"|

|align="left"|White Snow

|align="left"|

|align="left"|21st Destroyer Division, 3rd Torpedo Squadron

|align="left"|

|align="left"|First Snow

|align="left"|

|align="left"|21st Destroyer Division, 3rd Torpedo Squadron

|align="left"|

|align="left"|Massed Clouds

|align="left"|

|align="left"|21st Destroyer Division, 3rd Torpedo Squadron

|align="left"|

|align="left"|Shore Wave

|align="left"|

|align="left"|19th Destroyer Division, 3rd Torpedo Squadron

|align="left"|

|align="left"|Shore Wave

|align="left"|

|align="left"|19th Destroyer Division, 3rd Torpedo Squadron

Ships sunk by Malaya Force

{|class="wikitable sortable"

|+Merchant ships attacked

! scope="col" width="120px" |Name

! scope="col" width="15px" |Year

! scope="col" width="120px" |Flag

! scope="col" width="15px" |GRT

! Notes

! colspan="5" |Northern Force

|align="left"|

|align="left"|1922

|align="left"|

|align="right"|7,718

|align="left"|6 April 1942, gunfire, 19°40′N, 86°50′E, sunk, 18† 82 surv

|align="left"|

|align="left"|1928

|align="left"|

|align="right"|5,381

|align="left"|6 April 1942, gunfire, 35 nmi E. of Cuttack. sunk, 1† 29 surv

|align="left"|Exmoor

|align="left"|1919

|align="left"|

|align="right"|4,986

|align="left"|6 March 1942, gunfire, sunk

|align="left"|

|align="left"|1938

|align="left"|

|align="right"|6,622

|align="left"|6 April 1942, gunfire, Bay of Bengal, sunk, 2† 81 surv

|align="left"|

|align="left"|1922

|align="left"|

|align="right"|9,066

|align="left"|6 April 1942, gunfire, 19°45′N, 86°27′E, sunk, 25† 154 surv

|align="left"|

|align="left"|1922

|align="left"|

|align="right"|4,921

|align="left"|6 April 1942, gunfire off Puri, sunk, 0† 57 surv

|align="left"|

|align="left"|1920

|align="left"|

|align="right"|2,410

|align="left"|6 April 1942, gunfire, off Puri, 3†

! colspan="5" |Central Force

|align="left"|

|align="left"|1928

|align="left"|

|align="right"|5,268

|align="left"| Damaged

|align="left"|

|align="left"|1939

|align="left"|

|align="right"|1,279

|align="left"|6 April 1942, gunfire, sunk, 13†

|align="left"|

|align="left"|1939

|align="left"|

|align="right"|1,279

|align="left"| Damaged

|align="left"|

|align="left"|1921

|align="left"|

|align="right"|5,491

|align="left"|6 April 1942, carrier aircraft, 17°48′N, 84°09′W, 24† 17 surv, sank

|align="left"|

|align="left"|1930

|align="left"|

|align="right"|6,245

|align="left"|6 April 1942, carrier aircraft, sunk, 15†

|align="left"|

|align="left"|1934

|align="left"|

|align="right"|5,082

|align="left"|5 April 1942, carrier aircraft 19°19′N, 85°46′E, 11† 33 surv, sank

|align="left"|

|align="left"|1909

|align="left"|

|align="right"|3,827

|align="left"|6 April 1942, damaged

|align="left"|

|align="left"|1920

|align="left"|

|align="right"|4,839

|align="left"|Damaged

|align="left"|

|align="left"|1915

|align="left"|

|align="right"|2,646

|align="left"|6 April 1942, carrier aircraft, 17°32′N, 82°50′E, no†

|align="left"|

|align="left"|1921

|align="left"|

|align="right"|5,686

|align="left"|7 April 1942, carrier aircraft, sunk, 0†

|align="left"|

|align="left"|1935

|align="left"|

|align="right"|3,471

|align="left"|6 April 1942, gunfire, 17°52′N, 83°40′E, sunk, 15† 107 surv

|align="left"|

|align="left"|1942

|align="left"|

|align="right"|2,073

|align="left"|8 April 1942, carrier aircraft, sunk, 0†

! colspan="5" |Southern Force

|align="left"|

|align="left"|1930

|align="left"|

|align="right"|4,434

|align="left"|6 April 1942, gunfire, 16°15′N, 82°09′E, sunk, 0† 40 surv

|align="left"|

|align="left"|1923

|align="left"|

|align="right"|7,726

|align="left"|6 April 1942, gunfire, carrier aircraft

|align="left"|

|align="left"|1919

|align="left"|

|align="right"|5,281

|align="left"|6 April 1942, gunfire, 16°03′N, 82°20′E, sunk, 13† 69 surv

|align="left"|

|align="left"|1925

|align="left"|

|align="right"|1,515

|align="left"|6 April 1942, gunfire, Bay of Bengal, scuttled, 0†

British order of battle

Army

{|class="wikitable sortable"

|+Ceylon garrison, March 1942

! scope="col" width="180px" |Unit

! scope="col" width="120px"|Flag

! scope="col" width="60px"|Type

! Notes

! colspan="4" |Ceylon Defence Force

|align="left"|Ceylon Light Infantry

|align="left"|

|align="left"|Infantry

|align="left"|

|align="left"|Ceylon Planters Rifle Corps

|align="left"|

|align="left"|Infantry

|align="left"|

|align="left"|Colombo Town Guard

|align="left"|

|align="left"|Infantry

|align="left"|

|align="left"|Ceylon Garrison Artillery

|align="left"|

|align="left"|Artillery

|align="left"|6-inch naval, 9.2-inch naval

|align="left"|65th Heavy AA Regt

|align="left"|

|align="left"|Anti-Aircraft

|align="left"|40 × 3.7-inch AA,, 4 × 3-inch 20 cwt AA

|align="left"|43rd Light AA Regt

|align="left"|

|align="left"|Anti-Aircraft

|align="left"|69 × Bofors 40 mm AA from March 1942

! colspan="4" |Indian Army

|align="left"|34th Indian Division

|align="left"|

|align="left"|Infantry

|align="left"|

|align="left"|21st (East Africa) Infantry Brigade

|align="left"|

|align="left"|Infantry

|align="left"|Attached to 34th Indian Division

! colspan="4" |Australian Army

! colspan="4" |6th Australian Division

|align="left"|16th Australian Brigade

|align="left"|

|align="left"|Infantry

|align="left"|

|align="left"|17th Australian Brigade

|align="left"|

|align="left"|Infantry

|align="left"|

Royal Air Force, Fleet Air Arm

{|class="wikitable sortable"

|+222 Group RAF

! scope="col" width="120px" |

! scope="col" width="160px"|Flag

! scope="col" width="80px"|Type

! scope="col" width="80px"|Base

! Notes

! colspan="5" |RAF

! colspan="5" |Colombo

|align="left"|11 Squadron

|align="left"|

|align="left"|Bomber

|align="left"|Racecourse

|align="left"|14 Blenheim Mk IV

|align="left"|30 Squadron

|align="left"|

|align="left"|Fighter

|align="left"|RAF Ratmalana

|align="left"|22 Hurricane Mk IIb, 8 shot down

|align="left"|258 Squadron

|align="left"|

|align="left"|Fighter

|align="left"|Racecourse

|align="left"|9 Hurricane Mk IIb, 5 Mk Ib, 8 shot down

! colspan="5" |Galle

|align="left"|202 Squadron

|align="left"|

|align="left"|Flying boat

|align="left"|RAF Koggala

|align="left"|1 Catalina

|align="left"|205 Squadron

|align="left"|

|align="left"|Flying boat

|align="left"|RAF Koggala

|align="left"|Catalina FV-R

|align="left"|413 Squadron

|align="left"|

|align="left"|Flying boat

|align="left"|RAF Koggala

|align="left"|3 Catalina

! colspan="5" |Netherlands Naval Aviation Service

|align="left"|-2

|align="left"|

|align="left"|Flying boat

|align="left"|RAF Koggala

|align="left"|(Aircraft Group-2 [GVT-2]) Catalina Y-64

|align="left"|-16

|align="left"|

|align="left"|Flying boat

|align="left"|RAF Koggala

|align="left"|(GVT-16) Catalinas Y-55, Y-56 and Y-57

! colspan="5" |Trincomalee

|align="left"|261 Squadron

|align="left"|

|align="left"|Fighter

|align="left"|RAF China Bay

|align="left"|1 Hurricane Mk I, 17 Mk IIb

|align="left"|273 Squadron

|align="left"|

|align="left"|Fighter

|align="left"|RAF China Bay

|align="left"|16 Fulmar Mk I, Mk II

|align="left"|788 Naval Air Squadron

|align="left"|

|align="left"|Torpedo-bomber

|align="left"|RAF China Bay

|align="left"|6 Swordfish, Albacore, 6 Swordfish shot down

|align="left"|803 Naval Air Squadron

|align="left"|

|align="left"|Carrier fighter

|align="left"|RAF China Bay

|align="left"|12 Fulmar Mk II

|align="left"|806 Naval Air Squadron

|align="left"|

|align="left"|Carrier fighter

|align="left"|RAF China Bay

|align="left"|12 Fulmar Mk II

|align="left"|814 Naval Air Squadron

|align="left"|

|align="left"|Torpedo-bomber

|align="left"|RAF China Bay

|align="left"|10 Swordfish ashore from

|align="left"|

|align="left"|Fighter

|align="left"|RAF China Bay

|align="left"|2 Martlet ashore from Indomitable

Eastern Fleet

{|class="wikitable sortable"

|+Eastern Fleet

! scope="col" width="120px"|Ship

! scope="col" width="160px"|Flag

! scope="col" width="200px"|Class

! Notes

! colspan="4" |Admiral James Somerville

! colspan="4" |Force A

|align="left"|

|align="left"|Flag

! colspan="4" |Heavy cruisers

|align="left"|

! colspan="4" |Light cruisers

|align="left"|

! colspan="4" |Destroyers

|align="left"|

|align="left"|F-class destroyer

|align="left"|

|align="left"|H-class destroyer

|align="left"|

|align="left"|N-class destroyer

|align="left"|

|align="left"|N-class destroyer

|align="left"|

|align="left"|P-class destroyer

|align="left"|

|align="left"|P-class destroyer

|align="left"|

! colspan="4" |Vice-Admiral Algernon Willis

! colspan="4" |Force B

|align="left"|

|align="left"|Aircraft carrier

|align="left"|12 Fairey Swordfish, 10 ashore, 2 u/s

|align="left"|

! colspan="4" |Light cruisers

|align="left"|

! colspan="4" |Destroyers

|align="left"|

|align="left"|A-class destroyer

|align="left"|

|align="left"|D-class destroyer

|align="left"|

|align="left"|F-class destroyer

|align="left"|

|align="left"|G-class destroyer

|align="left"|

|align="left"|N-class destroyer

|align="left"|

|align="left"|S-class destroyer

|align="left"|

|align="left"|V-class destroyer

|align="left"|

Eastern Fleet aircraft

{|class="wikitable sortable"

|+ Naval Air Squadrons

! scope="col" width="120px" |

! Type

! Notes

! colspan="5" |

|align="left"|818 Naval Air Squadron

|align="left"|9 Fairey Albacore

|align="left"|Torpedo-bomber

|align="left"|820 Naval Air Squadron

|align="left"|12 Fairey Albacore

|align="left"|Torpedo-bomber

|align="left"|888 Naval Air Squadron

|align="left"|12 Martlet Mk II

|align="left"|Fighter

! colspan="5" |

|align="left"|800 Naval Air Squadron

|align="left"|12 Fairey Fulmar Mk II

|align="left"|Fighter

|align="left"|827 Naval Air Squadron

|align="left"|12 Fairey Albacore

|align="left"|Torpedo-bomber

|align="left"|831 Naval Air Squadron

|align="left"|12 Fairey Albacore

|align="left"|Torpedo-bomber

|align="left"|880 Naval Air Squadron

|align="left"|9 Sea Hurricane Mk Ib

|align="left"|Fighter

! colspan="5" |

|align="left"|814 Naval Air Squadron

|align="left"|12 Fairey Swordfish Mk I

|align="left"|2 u/s, 10 at China Bay

Notes

Footnotes

Bibliography

Books

Journals

Websites

External links

Order of battle
WW2DB.com: Raids into Indian Ocean
Royal Air Force History: Battle for Ceylon

Background

British Ceylon (Sri Lanka)

Japanese preparations

2nd Submarine Squadron

British preparations

Raid

26 March − 3 April

4 April

5 April

Cornwall and Dorsetshire

5 April, afternoon

6–8 April

9 April

Trincomalee

At sea

Japanese withdrawal

Associated operations

Malay Force

2nd Submarine Squadron

Aftermath

Analysis

Casualties

Japanese order of battle

Southern Force

Support Force

Kidō Butai cover force

Japanese carrier aircraft

Supply Force ()

Submarine Unit C

Ships sunk, 5 April 1942

Air raids, 9 April 1942

Warships

Merchant ships

Malaya Unit Striking Force

Malaya Force groups

Replenishment Unit

Guard Unit

Ships sunk by Malaya Force

British order of battle

Army

Royal Air Force, Fleet Air Arm

Eastern Fleet

Eastern Fleet aircraft

Notes

Footnotes

Bibliography

Books

Journals

Websites

Further reading

External links