View source for Indian Ocean raid

{{redirect|Operation C|the 1991 video game|Operation C (video game)}}
{{for|the later Japanese raid|Indian Ocean raid (1944)}}
{{short description|1942 raid of Allied shipping by the Imperial Japanese Navy}}
{{Use dmy dates|date=June 2020}}
{{Use British English|date=September 2015}}
{{Infobox military conflict
| conflict          = Indian Ocean raid
| partof            = the [[Pacific War|Pacific Theatre]] of [[World War II]]
| image             = Dorsetshire&Cornwall.jpg
| image_upright        = 1.23
| caption           = British [[heavy cruiser]]s {{HMS|Dorsetshire|40|6}} and {{HMS|Cornwall|56|2}} under Japanese air attack and heavily damaged on 5 April 1942.
| date              = 31 March – 10 April 1942
| place             = [[Indian Ocean]] and [[British Ceylon]]
| result            = Japanese victory
| combatant1        = {{flag|United Kingdom}}
* {{flag|British Ceylon}}
{{flag|Australia}}<br />{{flagdeco|Netherlands}} [[Dutch government-in-exile|Netherlands]]<br>{{flag|United States|1912}}<br>{{flag |Canada|1921}}
| combatant2        = {{flagicon|Empire of Japan}} [[Empire of Japan|Japan]]
| commander1        = [[James Somerville (admiral)|James Somerville]]
| commander2        = [[Chūichi Nagumo]]<ref name="Boyd_373"/><br />[[Mitsuo Fuchida]]
| units1            = {{flagicon|United Kingdom|naval}} [[Eastern Fleet]]
| units2            = {{flagicon|Empire of Japan|naval}} [[Kido Butai|Combined Fleet]]
| strength1         = 2 [[aircraft carrier|carriers]]<br />1 [[light aircraft carrier|light carrier]]<br />5 [[battleship]]s<br />7 [[cruiser]]s<br />15 [[destroyer]]s<br />7 [[submarine]]s<br />100+ [[Military aircraft|aircraft]]<br /> 30 smaller warships<br />50+ [[merchant ship]]s.
| strength2         = 5 carriers<br />1 light carrier<br />4 battleships<br />11 cruisers<br />23 destroyers<br />5 submarines<br /> 275 aircraft
| casualties1       = 1 light carrier sunk<br />2 [[heavy cruiser]]s sunk<br />2 destroyers sunk<br />1 [[Armed Merchant Cruiser]] (AMC) sunk<br />1 [[corvette]] sunk<br />1 [[Sloop-of-war|sloop]] sunk<br />20 merchant ships sunk<br />54 aircraft destroyed<br />825 killed
| casualties2       = 18 aircraft destroyed<br />31 aircraft damaged<br />32 killed
| campaignbox       =
}}
{{Campaignbox Pacific 1941}}
{{Campaignbox South-East Asia}}
{{Campaignbox Indian Ocean Theatre}}
{{Campaignbox South-East Asian Theatre}}

The '''Indian Ocean raid''', also known as '''Operation C'''<ref name="Boyd_364"/> or '''Battle of Ceylon''' in Japanese, was a naval sortie carried out by the [[Imperial Japanese Navy]] (IJN) from 31 March to 10 April 1942. Japanese aircraft carriers under Admiral [[Chūichi Nagumo]] struck Allied shipping and naval bases around [[British Ceylon]], but failed to locate and destroy the bulk of the British [[Eastern Fleet]]. The Eastern Fleet, commanded by Admiral Sir [[James Somerville (admiral)|James Somerville]], was forewarned by intelligence and sailed from its bases prior to the raid; its attempt to attack the Japanese was frustrated by poor tactical intelligence.

Following the attack, the British expected a major Japanese offensive in the [[Indian Ocean]]. The main base of the Eastern Fleet relocated to [[East Africa]], and Ceylon was reinforced, but Somerville kept his fast carrier division, ''Force A'', "...in [[Indian Ocean|Indian waters]], to be ready to deal with any attempt by the enemy to command those waters with light forces only."<ref name="Roskill_29">Roskill, p. 29</ref> However, the Japanese had no short-term plans to follow up on their success, and within the year operations in the Pacific made it impossible to do so.

==Background==
===Strategic situation===
The island of [[Ceylon]] was strategically important, since it commanded the Indian Ocean. Thus it controlled access to India, the vital Allied shipping routes to the [[Middle East]] and the oilfields of the [[Persian Gulf]]. Ceylon held most of the British Empire's resources of [[rubber]]. An important harbour and naval base, [[Trincomalee]], was located on the island's eastern coast. Japanese propaganda had an effect on some of the Sinhalese population, who now awaited their arrival.

The [[fall of Singapore]] on 15 February 1942 broke the United Kingdom's eastern defensive perimeter of the [[Bay of Bengal]]; and the [[Japanese occupation of the Andaman Islands]] on 23 March gave Japan control of the [[Andaman Sea]], enabling ships to resupply Japanese troops in the [[Burma Campaign]] for control of [[India]]. Both German and British authorities anticipated Japanese capture of Ceylon to solidify control of the Bay of Bengal and disrupt British resupply for defence of India, [[Australia]], and perhaps the Middle East. Ceylon was hastily garrisoned by Australian troops returning from North Africa; and {{HMS|Indomitable|R92|6}} was relieved of naval duties to serve as a high-speed aircraft ferry shuttling available planes to Ceylon.<ref>{{cite book |last=Churchill |first=Winston |author-link =Winston Churchill |title =The Hinge of Fate |url=https://archive.org/details/hingeoffate00chur |url-access=registration |publisher =Houghton Mifflin Company |date =1950 |location =Boston |pages =[https://archive.org/details/hingeoffate00chur/page/138 138], 172–178 }}</ref>

Japanese intentions to mount a major offensive into the Indian Ocean were placed on hold in March 1942; strong naval forces were needed in the western Pacific against the United States, and the [[Imperial Japanese Army]] (IJA) refused to allocate troops for an invasion of Ceylon. In response, the IJN developed Operation C, a plan for an aggressive raid into the Indian Ocean in early April. Operation C aimed to destroy the British [[Far East Fleet (United Kingdom)|Eastern Fleet]], and disrupt British lines of communications in the Bay of Bengal in support of the Burma Campaign.<ref name="Boyd_364">Boyd, p. 364</ref>

British intelligence correctly assessed the Japanese strategy. The Americans were notified; the [[Doolittle Raid]] – which was already in progress – took on the additional role of a diversion.<ref name="Boyd_364"/>

===Japanese preparations===
Admiral [[Isoroku Yamamoto]] issued the initial order to proceed with Operation C to the IJN's southern force, commanded by Admiral [[Nobutake Kondō]], on 9 March 1942. By 16 March, the plan was to depart from [[Staring Bay]], [[Sulawesi|Celebes]], on 26 March for an attack on Colombo ("C day") on 5 April.<ref name="Boyd_366">Boyd, p. 366</ref> The Japanese expected to destroy the British Eastern Fleet in port.<ref name="Boyd_381">Boyd, p. 381</ref>

The Japanese force, commanded by Admiral [[Chūichi Nagumo]], had a core of five aircraft carriers; {{Ship|Japanese aircraft carrier|Akagi||2}}, {{Ship|Japanese aircraft carrier|Shōkaku||2}} and {{Ship|Japanese aircraft carrier|Zuikaku||2}} in Carrier Division 5, and {{Ship|Japanese aircraft carrier|Sōryū||2}} and {{Ship|Japanese aircraft carrier|Hiryū||2}} in Carrier Division 2.<ref name="Boyd_373">Boyd, p. 373</ref> The carriers were accompanied by all four {{sclass|Kongo|battleship|2}}s, and both {{sclass|Tone|cruiser|2}}s.<ref name="Boyd_367">Boyd, p. 367</ref>

Japanese intelligence on the composition of the British Eastern Fleet in the Indian Ocean<ref name="Tully_Yu_5">Tully and Yu, p. 5</ref> was reasonably accurate, while overestimating the air strength on Ceylon.<ref name="Boyd_381">Boyd, p. 381</ref> The 19 March operational order vaguely advised that a "considerable" portion of British naval and air forces in the Indian Ocean were "deployed in Ceylon area".<ref name="Tully_Yu_5"/>

The Japanese stationed reconnaissance submarines outside of the known British anchorages at Colombo and Trincomalee; their effectiveness was limited.<ref name="Boyd_369">Boyd, p. 369</ref> At least one submarine was sent to scout the [[Maldive Islands]] but failed to detect [[Gan (Addu Atoll)|Port T]] at [[Addu Atoll]].<ref name="Boyd_370">Boyd, p. 370</ref>

At the same time as Operation C, the IJN also dispatched Malay Force under the command of Vice Admiral [[Jisaburō Ozawa]]. His force consisted of the aircraft carrier {{Ship|Japanese aircraft carrier|Ryūjō||2}}, six [[cruiser]]s, and four destroyers to destroy shipping in the Bay of Bengal on 1 April. Malay Force was not part of Operation C.<ref>Shores, Cull & Izawa, Vol. II, pp. 393, 408–411</ref>

In 3 days, Ozawa's force managed to sink 23 merchant ships (20 in a single day),<ref name=":0">{{Cite journal |last=Black |first=Jeremy |date=2009 |title=Midway and the Indian Ocean |url=https://www.jstor.org/stable/26397057 |journal=Naval War College Review |volume=62 |issue=4 |pages=135 |jstor=26397057 |issn=0028-1484 |archive-date=4 January 2024 |access-date=4 January 2024 |archive-url=https://web.archive.org/web/20240104040347/https://www.jstor.org/stable/26397057 |url-status=live }}</ref> totaling over 130,000 gross registered tons.{{sfn|Warner|Bennett|Macyntire|Uehling|1976|p=154}} In addition, April saw 32,000 tons of shipping sunk by Japanese submarines off India's west coast.<ref name=":0" /> ''Ryūjō''{{'}}s aircraft also bombed the ports of [[Cocanada]] and [[Vizagapatam]], causing relatively minor damage.<ref name=":0" /> The tonnage and number of ships sunk by Malay Force, are comparable to that of the 3-month long [[Operation Berlin (Atlantic)|Operation Berlin]] raid conducted by [[Scharnhorst-class battleship|two battleships]] of the ''[[Kriegsmarine]]'' from January to March 1941.{{sfn|Macintyre|1975|pp=104–106}} In both raids against merchant shipping, Allied merchant ships were not sailing in convoys escorted by large vessels.{{sfn|Ireland|2004|p=48}}

===British preparations===
[[File:Pacific War - Southern Asia 1942 - Map.jpg|thumb|upright=1|Japanese operation in the Northern Indian Ocean and Bay of Bengal in 1942. Nagumo's forces are shown at the bottom of the map.]]
The reinforcement of the British Eastern Fleet depended on transfers from Britain and the Mediterranean, a reflection of active warzones and the demands on the Royal Navy's (RN) resources. In late-December 1941, a reassessment of the threat posed by Japan envisioned transferring the majority of the RN's heavy units to the Eastern Fleet. Matters were made urgent by the [[Attack on Pearl Harbor|crippling]] of the [[United States Pacific Fleet]]'s battle line at [[Pearl Harbor]], which exposed the weak forces in Malaya to attack. Heavy units were freed up by American reinforcements in the Atlantic. The construction programs of the late-1930s were also starting to yield new heavy units. The Mediterranean yielded far fewer reinforcements than expected due to serious losses in that theatre in 1941.<ref name="Boyd_356">Boyd, p. 356</ref>

The Eastern Fleet that Vice Admiral Sir [[James Somerville (admiral)|James Somerville]] assumed command of in March 1942 was smaller than what had been envisioned in December 1941. Somerville divided the fleet into two groups, based on speed. The faster "Force A" included the [[aircraft carrier]]s {{HMS|Formidable|67|6}} and ''Indomitable'', the modernized [[battleship]] {{HMS|Warspite|03|6}} (as [[flagship]]), as well as the modern cruisers and destroyers. The slower "Force B" was formed around the old carrier {{HMS|Hermes|95|6}} and four unmodernized {{sclass|Revenge|battleship|2}}s. A few [[submarine]]s were also available.<ref name="Boyd_365">Boyd, p. 365</ref><ref name="Boyd_370"/><ref>Somerville, Sir James. [http://www.naval-history.net/xDKWD-EF1942-Introduction.htm ''Report of Proceedings (ROP) Of Eastern Fleet – 1942''] {{Webarchive|url=https://web.archive.org/web/20180228000034/http://naval-history.net/xDKWD-EF1942-Introduction.htm |date=28 February 2018 }}</ref><ref>Roskill, p. 23</ref> The ships had never operated together before, and both ship and air crews were deficient in training.<ref name="Boyd_365"/>

Allied intelligence accurately assessed the strength of the Japanese force.<ref name="Boyd_366"/> Somerville planned to evade the Japanese during the day and close to launch torpedo strikes with [[List of World War II British naval radar#ASV II|radar-equipped]] [[Fairey Albacore]] bombers during the night.<ref name="Boyd_370"/> However, the plan was based on information provided by the [[Far East Combined Bureau]] (FECB), which identified only two carriers in the Japanese force. FECB also believed the Japanese would sail from Staring Bay on 21 March for a "C day" of 1 April. Thus, Somerville sailed early expecting to fight a smaller and manageable enemy force, particularly in aircraft strength.<ref name="Boyd_366"/> As such, Somerville likely did not see his plan as incompatible with his orders from the [[British Admiralty|Admiralty]], which were to protect the lines of communications in the Indian Ocean, and to maintain the Eastern Fleet as a [[fleet in being]] by avoiding unnecessary risks.<ref name="Boyd_366"/>

The British recognized the threat of Japanese carrier-borne air attack on Ceylon after the strike on Pearl Harbor, and the island's air defences were reinforced. On 7 December 1941, air defences consisted of four obsolescent three-inch [[Anti-aircraft warfare|anti-aircraft]] guns – at Trincomalee – with neither fighters nor radar.<ref name="Stuart_2014_33">Stuart 2014, p. 33</ref> By 4 April, there were 67 [[Hawker Hurricane]]s and 44 [[Fairey Fulmar]] fighters, a radar station each at Colombo and Trincomalee, and 144 anti-aircraft guns;<ref name="Stuart_2014_35">Stuart 2014, p. 35</ref> 37 or 38 Hurricanes were serviceable around Colombo on 5 April.<ref name="Stuart_2014_44">Stuart 2014, p. 44</ref> The fighters were divided into three [[Royal Air Force]] (RAF) squadrons of Hurricanes (two at Colombo, and one at Trincomalee), and two squadrons of RN [[Fleet Air Arm]] (FAA) Fulmars.<ref name="Roskill_26"/> In the same time frame, other air forces increased from eight obsolete [[torpedo bomber]]s,<ref name="Stuart_2014_33"/> to seven [[Consolidated PBY Catalina]] flying boats, 14 [[Bristol Blenheim]] IV bombers, and 12 [[Fairey Swordfish]] torpedo bombers.<ref name="Stuart_2014_44"/> On the eve of battle, RAF forces were part of [[No. 222 Group RAF|222 Group]] ([[Air Vice-Marshal]] [[John D'Albiac]]).<ref name="Stuart_2014_37">Stuart 2014, p. 37</ref>

==Raid==

===First moves===
[[File:GF in Indian Ocean, 1942.jpg|thumb|The Japanese strike force advancing to the Indian Ocean, 30 March. Ships shown from left to right are: ''Akagi'', ''Sōryū'', ''Hiryū'', {{ship|Japanese battleship|Hiei||2}}, {{ship|Japanese battleship|Kirishima||2}}, ''Haruna'', and {{ship|Japanese battleship|Kongō||2}}. Taken from ''Zuikaku''.]]
The Japanese sailed from Staring Bay on 26 March as planned.<ref name="Boyd_367"/> Somerville sailed on 30 March in expectation of an attack on 1 April, and deployed his fleet in a patrol area {{convert|100|mi|km}} south of Ceylon.<ref name="Boyd_368">Boyd, p. 368</ref> Ceylon air defences and forces went on alert,<ref name="Stuart_2014_36">Stuart 2014, p. 36</ref> with land-based aerial reconnaissance concentrating on the southeast, where the Japanese were expected to approach to launch strikes at Colombo and Trincomalee.<ref name="Boyd_368"/> Late on 2 April, the British retired toward Port T – {{convert|600|mi|km}} southwest of Ceylon – to refuel.<ref name="Boyd_368"/> Somerville also detached various ships to resume previous commitments; the heavy cruisers {{HMS|Cornwall|56|6}} and {{HMS|Dorsetshire|40|6}} were sent to Colombo, and ''Hermes'' to Trincomalee.<ref name="Boyd_370"/> Air defences stood down, although Catalina patrols continued.<ref name="Stuart_2014_36"/>

At about 16:00 on 4 April, [[PBY Catalina]] [[flying boat]] (AJ155/QL-A) from the [[Royal Canadian Air Force]]'s (RCAF) [[413 Transport and Rescue Squadron|413 Squadron]] flown by [[Squadron Leader]] [[Leonard Birchall]] spotted Nagumo's fleet {{convert|360|mi|nmi km|lk=on|abbr=on}} south-east of Ceylon<ref name="Stuart_2014_37"/><ref name="Boyd_368"/> on a course that would have entered Somerville's previous patrol area from the south.<ref name="Boyd_375">Boyd, p. 375</ref> The Catalina transmitted the sighting, but not the size of the fleet, before being shot down.<ref name="Boyd_368"/> At this time, Somerville was refuelling at Port T; Force A sailed eastward toward the Japanese upon receiving the sighting;<ref name="Boyd_370"/> Force B could not be ready until 5 April.<ref name="Roskill_26">Roskill, p. 26</ref> Catalina FV-R from [[No. 205 Squadron RAF|205 Squadron RAF]] took off at 17:45 to shadow the Japanese fleet, making its first report at 22:37 on 4 April, and a final report at 06:15 on 5 April while {{convert|110|mi|nmi km|lk=on|abbr=on}} from Ceylon. FV-R was shot down about 90 minutes after the final report.<ref name="Stuart_2014_37"/>

Within an hour of QL-A's report, D'Albiac met with his subordinates to discuss an anticipated Japanese strike after dawn. 222 Group issued a warning to subordinate units before midnight, and units went on alert at 04:00 on 5 April.<ref name="Stuart_2014_37"/><ref name="Stuart_2014_38">Stuart 2014, p. 38</ref> On the morning of 5 April, six Swordfish from [[788 Naval Air Squadron]] (788 NAS) began relocating from [[China Bay Airport|China Bay]], near Trincomalee, to Colombo, in preparation for a strike on the Japanese fleet.<ref name="Stuart_2014_42">Stuart 2014, p. 42</ref> Admiral [[Geoffrey Layton]], on Ceylon, ordered ships put to sea to avoid being attacked in harbour. ''Cornwall'' and ''Dorsetshire'', which had just reached Colombo, were sent to rejoin Force A;<ref name="Roskill_26"/> they sailed late on 4 April.<ref name="Roskill_27">Roskill, p. 27</ref> ''Hermes'' sailed from Trincomalee and was ordered to hide northeast of Ceylon.<ref name="Roskill_26"/>

The Japanese did not perform an aerial reconnaissance sweep along their intended course on the afternoon of 4 April, and a planned reconnaissance of Colombo harbour by cruiser floatplanes was cancelled.<ref name="Boyd_369"/> The Japanese realized surprise was lost after intercepting a signal from Colombo asking QL-A to repeat its report.<ref name="Stuart_2006_69">Stuart 2006, p. 69</ref>

===Attack on Colombo===
{{main|Easter Sunday Raid}}
Japanese intelligence on the morning of 5 April 1942 indicated that British carriers were absent, and the Japanese morning air search was limited accordingly.<ref name="Tully_Yu_5"/> At dawn, Japanese aerial reconnaissance aircraft flew off to the south-west and north-west; they would fly out to a maximum of {{convert|200|mi|km}} over the next few hours. A reconnaissance Fulmar launched 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 {{convert|140|mi|km}} ahead of Force A.<ref name="Boyd_372">Boyd, p. 372</ref>

Shortly after 06:00<ref name="Boyd_371">Boyd, p. 371</ref> Nagumo's force began launching 91 bombers and 36 fighters for the strike on Colombo.<ref name="Roskill_26"/> British early warning failed to detect and identify the incoming strike,<ref name="Stuart_2014_38-41">Stuart 2014, p. 38–41</ref> forcing British pilots to [[Scrambling (military)|scramble]] under fire when the first Japanese aircraft appeared over them at 07:45. The effective defence of the [[Ratmalana Airport|Ratmalana]] airbase by British fighters<ref name="Stuart_2014_42-43">Stuart 2014, p. 42–43</ref> left the harbour exposed. The [[armed merchant cruiser]] {{HMS|Hector|F45|6}},<ref name="Stuart_2014_43"/> the Norwegian tanker ''Soli''<ref name="Stuart_2014_47">Stuart 2014, p. 47</ref> and the old destroyer {{HMS|Tenedos|H04|6}} were sunk; three other ships were damaged. The port was damaged<ref name="Stuart_2014_43">Stuart 2014, p. 43</ref> but was not put out of action.<ref name="Roskill_26"/> 20 of the 41 British fighters that took off were destroyed.<ref name="Stuart_2014_33"/> At least one fighter was damaged and made incapable of flight while attempting to take off. The six Swordfish of 788 NAS arrived during the battle and were shot down.<ref name="Stuart_2014_42"/> The Japanese lost seven aircraft.<ref name="Stuart_2014_33"/>

Nagumo changed course to west-southwest at 08:30<ref name="Boyd_371"/> – unknowingly causing the opposing fleets to steam toward one another<ref name="Boyd_373"/> – and recovered the Colombo strike from 09:45 to 10:30.<ref name="Boyd_373"/>

The size of the airstrike on Colombo was Somerville's first concrete evidence that the Japanese force contained more than the two carriers he expected. Nonetheless he continued to steam toward the enemy at 18 knots. Radar-based fighter direction would allow Force A to avoid surprise attack by neutralizing shadowing Japanese aircraft.<ref name="Boyd_372"/>

===Loss of ''Dorsetshire'' and ''Cornwall''===
[[File:HMS Cornwall - 1942 - WWII.jpg|thumb|{{HMS|Cornwall|56|6}} burning and sinking on 5 April 1942]]
At 10:00, an aircraft from ''Tone'' searching the southwest area spotted and began shadowing ''Dorsetshire''<nowiki>'</nowiki>s force; the aircraft reported that the cruiser was heading southwest and making 24 knots.<ref name="Boyd_373"/> The cruisers reported the shadower, but had no means to drive it off.<ref name="Roskill_27"/> Nagumo increased speed from 24 to 28 knots upon receiving the sighting. Carrier Division 5's reserve strike force was ordered rearmed with anti-ship torpedoes, replacing the high explosive bombs intended for a second strike on Colombo. The rearming encountered delays, and the strike was carried out by Carrier Division 2 instead; ''Soryu'' and ''Hiryu'' began launching dive bombers at 11:45.<ref name="Boyd_373"/> Force A radar detected the air strike on ''Dorsetshire''<nowiki>'</nowiki>s force at 13:44, putting the aircraft {{convert|34|mi|km}} to the northeast.<ref name="Boyd_372"/> ''Cornwall'' and ''Dorsetshire'' were sunk at 1400;<ref name="Boyd_374">Boyd, p. 374</ref> ultimately 424 officers and crew were lost.<ref name="Roskill_27"/>

The Japanese missed an opportunity to find Force A after sinking the cruisers. The aircraft shadowing the cruisers flew another {{convert|50|mi|km}} along the cruisers' course before returning to ''Tone''. It would have detected Force A if it had flown southwest another ten minutes.<ref name="Boyd_374"/>

Nagumo recovered the strike against the cruisers at 14:45.<ref name="Boyd_374"/>

===Nagumo evades Somerville===
Somerville launched four Albacores from ''Indomitable'' at 14:00 to search an arc to the northeast out to {{convert|200|mi|km}}. Nagumo's southeasterly course would have taken the Japanese fleet right through the centre of the arc. However, at 15:00 or 15:30, Nagumo changed course to the southwest. Carrier Division 2 did not immediately follow; it performed a series of kinking manoeuvres starting at 15:00 that initially took it northwest.<ref name="Boyd_374"/> Carrier Division 2 was spotted by the two northerly Albacores around 16:00. ''Hiryū'' launched [[Mitsubishi A6M Zero]] fighters to intercept the scouts; one Albacore was damaged at 16:04, and the other shot down at 16:28 without reporting.<ref name="Boyd_377">Boyd, p. 377</ref> The two southernmost Albacores missed Nagumo's main body.<ref name="Boyd_374"/>

Somerville did not receive the damaged Albacore's sighting report until 16:55; the report gave the position of Carrier Division 2 with reasonable accuracy, placed the Japanese {{convert|125|mi|km}} away, but contained no other data. At 17:00 he received [[signals intelligence]] (SIGINT) from Colombo reporting the Japanese course at 14:00 as southwesterly at 24 knots. Somerville ordered a course change to the southwest at 17:26, not knowing that Nagumo's main body was {{convert|120|mi|km}} away, and that Carrier Division 2 was only {{convert|100|mi|km}} away. The course change was presumably to maintain distance between a superior enemy that was believed to be still closing, or to cover Port T from attack, but it also meant the British lost an opportunity to meet the enemy; had Force A continued on its easterly course, Carrier Division 2 would have passed right in front of it at 21:00 at range of about {{convert|20|mi|km}}.<ref name="Boyd_377"/>

The damaged Albacore landed at 17:45, less than a half-hour before sunset, and the crew was debriefed. There were two resulting revisions to the 16:00 sighting, which were transmitted to Somerville at 18:00 and 18:17 respectively, and differed significantly from the other and the original report. The final revision correctly identified the two carriers of Carrier Division 2 – which Somerville likely realized to be only part of the enemy force – but also claimed they were heading toward the northwest at a position {{convert|25|mi|km}} or the original sighting. The course heading conflicted with the first revision, which suggested a course toward the southeast. Late on 5 April, FECB decrypted a [[Japanese naval codes|JN 25B]] message containing Nagumo's planned movement on 6 April, but this did not aid Somerville as the transmission to the fleet was garbled. Somerville declined to launch a strike based on poor information, and opted to head northwest in pursuit. One radar-equipped aircraft was launched to search a northern arc out to {{convert|200|mi|km}}. Later, aircraft were sent to search the easterly arc. By this time it was too late to reestablish contact with the Japanese.<ref name="Boyd_379">Boyd, p. 379</ref>

For the Japanese, too, there was a lost opportunity to find the British before night fell. Nagumo did not order a search for the British carriers at the appearance of British carrier-based aircraft. Search aircraft might require homing signals from the carriers to return, homing signals which the enemy could use to locate the Japanese. The Japanese continued southeast at 20 knots completely unaware of the presence of Force A.<ref name="Boyd_378">Boyd, p. 378</ref> Carrier Division 2 rejoined the main body's track at 18:00,<ref name="Boyd_376">Boyd, p. 376</ref> and caught up at 22:00 {{convert|180|mi|km}} due east of Force A.<ref name="Boyd_379"/> The Japanese circled wide to the south and then east in preparation for striking Trincomalee.<ref name="Roskill_27"/> The Japanese suspected the presence of British carriers, and on the morning of 6 April they launched a much denser<ref name="Tully_Yu_5"/> westward<ref name="Tully_Yu_6">Tully and Yu, p. 6</ref> air search, but found nothing.<ref name="Tully_Yu_5"/> Further searches on route to Trincomalee were equally unsuccessful as the British carriers were by that time far to the west.<ref name="Roskill_27"/>

By 6 April, British SIGINT indicated the Japanese force contained four carriers and three battleships, a force Somerville clearly realized as beyond the Eastern Fleet's capability to engage without undue risk. The declining serviceability of his fighter force also reinforced his caution.<ref name="Boyd_380">Boyd, p. 380</ref> Even so, Somerville did not immediately withdraw or return to port. Force B rejoined early on 6 April. In the afternoon 1,122 survivors<ref name="Roskill_27"/> from ''Dorsetshire''<nowiki>'</nowiki>s force were recovered, while maintaining a look-out for the superior enemy force with all-around air reconnaissance.<ref name="Boyd_384">Boyd, p. 384</ref> 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.<ref name="Roskill_27"/>

===Attack on Trincomalee===
By 8 April, the Eastern Fleet had withdrawn and the Japanese fleet was approaching Trincomalee from the east.<ref name="Roskill_27">Roskill, p. 27</ref><ref name="Roskill_28">Roskill, p. 28</ref><ref name="Stuart_2006_72">Stuart 2006, p. 72</ref> The Japanese fleet was detected by a RAF Catalina at 15:17 on 8 April and the harbour at Trincomalee was cleared that night.<ref name="Stuart_2006_72"/> ''Hermes'', escorted by {{HMAS|Vampire|D68|6}}, was sent south along the coast.<ref name="Roskill_28"/> The Japanese air search on the morning of 9 April was limited as on 5 April, as British carriers were no longer expected.<ref name="Tully_Yu_5"/> The Japanese strike group of 132 aircraft was detected at 07:06 on 9 April by the radar of AMES 272 at a range of {{cvt|91|mi}}.<ref name="Stuart_2006_72"/><ref name="Stuart_2014_43"/> The defence sent 17 Hurricanes and six Fulmars that took off in time and inflicted the first kills of the battle when a section of Hurricanes attacked three Zeroes and shot down two.<ref name="Stuart_2006_72"/><ref name="Stuart_2014_43"/> The China Bay airbase and the port were severely bombed and the monitor {{HMS|Erebus|I02|6}} was damaged.<ref name="Stuart_2006_72"/> [[SS Sagaing|SS ''Sagaing'']], a merchant ship carrying aircraft and ammunition, was set on fire and abandoned.<ref name="rogersAU">{{cite news |last1=Rogers |first1=James |title=Huge World War II shipwreck raised from the depths in massive salvage operation |url=https://www.news.com.au/technology/science/archaeology/huge-world-war-ii-shipwreck-raised-from-the-depths-in-massive-salvage-operation/news-story/66d058084186e582172b77f32d517bf9 |access-date=7 April 2018 |agency=news.com.au |publisher=news.com.au |date=3 April 2018}}</ref> Eight Hurricanes and a Fulmar were lost, although no serviceable fighters were lost on the ground and the Japanese lost four aircraft.<ref name="Stuart_2006_72"/><ref name="Stuart_2014_42"/> At 07:16 another Catalina from 413 Squadron RCAF spotted the Japanese fleet, but was shot down while reporting.<ref name="Stuart_2006_73"/>

===Blenheims attack the Japanese carriers===
Around 10:25, nine unescorted Blenheims from [[No. 11 Squadron RAF|11 Squadron RAF]]<ref name="Stuart_2006_73"/> attacked Nagumo's force. They were not detected inbound by the [[combat air patrol]] (CAP). ''Hiryū'' spotted the aircraft but failed to relay a warning to the other ships and the attack achieved surprise.<ref name="Parshall_145">Parshall, p. 145</ref> The bombers attacked ''Akagi'' at {{cvt|11000|ft}}; the bombs fell close to the target with no hits.<ref name="Shores_1993_426">Shores 1993, p. 426–427</ref><ref name="Parshall_145"/> Four bombers were shot down over the carriers by CAP A6M2 Zeroes (two of which were claimed by [[Kaname Harada]]), and another by Japanese aircraft returning from the strike on ''Hermes''. In return, a Zero was shot down near the carriers and another in the returning strike.<ref name="Shores_1993_426"/> This was the first time a Japanese carrier force had faced a concerted air attack.<ref name="Parshall_145"/>

===Loss of ''Hermes''===
[[File:HermesSinking.jpg|thumb|''Hermes'' sinking after Japanese air attack on 9 April 1942.]]
{{HMS|Hermes|95|2}} and {{HMAS|Vampire|D68|2}} were {{convert|65|mi|km}} away when Trincomalee was attacked. At 09:00 they reversed course.<ref name="Roskill_28"/> Shortly after the end of the attack on Trincomalee, an aircraft from {{ship|Japanese battleship|Haruna||2}} spotted the ships. A force of 80 [[Aichi D3A]] "Val" bombers, held in reserve on the Japanese carriers, attacked starting at 10:35.<ref name="Stuart_2006_72"/><ref name="Stuart_2006_73">Stuart 2006, p. 73</ref> Both were sunk before noon near [[Batticaloa]].<ref name="Stuart_2006_73"/><ref name="Hobbs_bac">{{cite book |last=Hobbs |first=David |year=2013 |title=British Aircraft Carriers |publisher=Seaforth Publishing |isbn=978-1-84832-138-0 |chapter=Chapter 7: Hermes}} (ebook)</ref> ''Hermes'' was lost with 307 men after being hit by over forty {{cvt|500|lb}} bombs. ''Vampire'' was lost with 8 men. The nearby [[hospital ship]] ''Vita'' rescued 600 men.<ref name="Hobbs_bac"/> The Japanese attack expanded to nearby ships. The [[Corvette#World War II|corvette]] {{HMS|Hollyhock|K64|6}} was hit by aircraft from ''Soryu'' and sunk with 53 men.<ref name="Hobbs_bac"/> Also sunk were the naval auxiliary ''Athelstone'', the  tanker ''British  Sergeant'', and the cargo ship ''Norviken''.<ref name="Stuart_2006_73"/> British land-based Fulmars arrived only after ''Hermes'' was sunk. Two Fulmars and four Vals were destroyed.<ref name="Stuart_2006_73"/> Nagumo disengaged after recovering the strike on ''Hermes''.<ref name="Stuart_2006_73"/>

==Aftermath==
===British reaction===
The Japanese inflicted disproportionate damage on the enemy. They damaged port facilities, sank one carrier and two cruisers, destroyed a third of enemy ground-based fighters and nearly all of the enemy ground-based strike aircraft. In addition, 23 merchant ships,<ref name="Boyd_384"/> totalling 112,312 tons,<ref name="Roskill_28"/> were sunk, including those by the separate Japanese Malay Force. In return, the Japanese lost only 18 aircraft (six fighters, ten dive-bombers and two high-level bombers), with damage to about 31 more. Conversely, they failed to destroy, or even locate, the main bulk of the British Eastern Fleet.<ref name="Boyd_384"/>

The British interpreted their position as precarious. Ceylon and the Eastern Fleet were required to safeguard the sea lines of communications through the Indian Ocean. The British expected the Japanese to continue threatening these lines. SIGINT suggested that the Japanese were preparing a deliberate advance across the Indian Ocean.<ref name="Boyd_385">Boyd, p. 385</ref> The raid demonstrated that the RAF was too weak to defend Ceylon and the naval anchorages,<ref name="Roskill_29"/> and that the navy was ill-prepared to meet a Japanese carrier force.<ref name="Boyd_388">Boyd, p. 388</ref>

The Eastern Fleet transferred its main base to [[Kilindini]], [[Kenya Colony|Kenya]] in East Africa, temporarily ceding the eastern Indian Ocean to the Japanese; from there it continued contesting control of the central Indian Ocean on better terms.<ref name="Boyd_385"/> Force A, including its two aircraft carriers, ''Indomitable'' and ''Formidable'', retired to Bombay,<ref name="Roskill_29"/> and Somerville regularly deployed a fast carrier force to the central Indian Ocean over the next six months, during which he operated from or near Ceylon for nearly half that time. On 18 April, naval planning accorded the Eastern Fleet the highest priority for reinforcement, which also included transferring most of the carriers from the Home Fleet and the Mediterranean, with the intention of returning to Ceylon in September.<ref name="Boyd_389">Boyd, p. 389</ref>

By June, Ceylon was defended by three RAF squadrons (64 aircraft, plus reserves), three strike squadrons (including one of Beauforts), and much improved radar and anti-aircraft defences.<ref name="Boyd_392">Boyd, p. 392</ref> Ground defences were manned by two Australian army brigades.<ref name="Boyd_391">Boyd, p. 391</ref>

The invasion scare was short-lived. British intelligence detected the movement of the Japanese carrier force eastward in mid-April, and their deployment in the Pacific in mid-May.<ref name="Boyd_393">Boyd, p. 393</ref> After the [[Battle of Midway]] in June, it was realized that there was no longer the threat of major Japanese naval activity in the Indian Ocean. In September, British intelligence predicted Japan would go over to the defensive. As a result, the Eastern Fleet was not reinforced as planned and, instead, shrank after early July.<ref name="Boyd_395">Boyd, p. 395</ref>

===Japanese reaction===
The Japanese did not exploit their victory as the British feared. The decision to postpone major operations in the Indian Ocean was upheld. The Japanese aircraft carriers required maintenance and replenishment after months of intensive operations,<ref name="Parshall_ch1">Parshall, ch. 1</ref> and there was already difficulty in maintaining the strength of frontline air units.<ref name="Parshall_ch5">Parshall, ch. 5</ref> Nagumo and officers such as [[Mitsuo Fuchida]] (commanding ''Akagi''{{'}}s air group) felt that the losses inflicted on the British did not justify the loss of experienced Japanese air crews.<ref>{{cite book| last=Perrett| first=Bryan| author-link=Bryan Perrett| title=Why the Japanese lost| publisher=Pen & Sword Military| location=Barnsley, UK| year=2014| page=114| isbn=978-1-78159-198-7}}</ref> Japanese attention also lay elsewhere. In early May, Japanese carriers fought the [[Battle of the Coral Sea]] in the southwest Pacific,<ref name="Parshall_ch1"/> followed in June by the Battle of Midway.<ref name="Boyd_395"/> In both cases, losses constrained Japanese options further. In June, the IJA developed a plan for an offensive in the Indian Ocean, including an invasion of Ceylon. The Germans were advancing in North Africa, which made an [[Axis powers|Axis]] link-up in the [[Middle East]] attractive. Resource constraints forced the IJN to reject it, especially once the [[Guadalcanal Campaign]] started.<ref name="Boyd_395"/>

The limit of Japanese operations in the Indian Ocean was against trade using submarines and [[armed merchant cruiser]]s.<ref name="BoydYoshida_90">Boyd and Yoshida, p. 90</ref> A submarine group patrolling off East Africa attacked the harbour at [[Diego-Suarez]], [[Madagascar]], while the Allies were fighting the [[Battle of Madagascar]].<ref name="BoydYoshida_88">Boyd and Yoshida, p. 89</ref> The Allies were motivated by fears that the Japanese might establish a base there to attack trade.<ref name="Boyd_392"/> Japanese attacks on trade enjoyed some success, but after 1942 the presence of large Japanese naval units in the Indian Ocean virtually ceased.<ref>{{cite journal |last1=Kowner |first1=Rotem |title=When Economics, Strategy, and Racial Ideology Meet: Inter-Axis Connections in the Wartime Indian Ocean |url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/BD54F874049F225713DD4801CE864DC2/S1740022817000067a.pdf/div-class-title-when-economics-strategy-and-racial-ideology-meet-inter-axis-connections-in-the-wartime-indian-ocean-a-href-fn1-ref-type-fn-a-div.pdf |journal=Journal of Global History |volume=12 |issue=2 |pages=240 |publisher=Cambridge University Press |doi=10.1017/S1740022817000067 |date=July 2017 |access-date=5 May 2019 |doi-access=free}}</ref>

===Criticism of Nagumo===
Nagumo's leadership has been characterized by Andrew Boyd as rigid and unimaginative, and contributed to the escape of the British Eastern Fleet. The manoeuvring of his fleet was mainly to facilitate strikes on Colombo and Trincomalee; the possibility that the enemy might be at sea was apparently not seriously considered. He failed to appreciate that the direction that ''Dorsetshire''{{'}}s force was sailing, and the later appearance of British carrier-based aircraft, were related. Furthermore, due to limited aerial reconnaissance, Nagumo had little concrete information of what was around him, especially to his front and exposed flanks. He was not served by the confidence that there was nothing else to be found outside of the few searches made.<ref name="Boyd_381"/>

The limited air searches conducted at the start of the battle reflected contemporary IJN practice, where the intensity of air searches was scaled according to expected threats. The stronger morning search on 6 April reflected the suspicion that British carriers might be present. The intensity of later air searches dropped off when the British carriers were not found and there was little expectation of encountering them. Ultimately, all navies suffered from inadequate air search planning during this period.<ref name="Tully_Yu_4-8">Tully and Yu, pp. 4–8</ref>

===Problems with Japanese carrier operations===
The raid also provided early examples of problems with Japanese carrier operations. Inadequate aerial reconnaissance failing to locate the enemy fleet in a timely fashion, the difficulty of rearming aircraft for a different mission at short notice, and the penetration of the CAP by enemy aircraft due to the lack of radar-directed fighter control would all recur at the [[Battle of Midway]].<ref name="Boyd_381"/>

===Criticism of Somerville===
Somerville's leadership was characterized by a willingness to take risks, bordering on recklessness. The initial deployment of the fleet on 30 March endangered the British fleet. Somerville was relying on radar – manned by inexperienced personnel – to locate the enemy and facilitate night strikes. If the Japanese approached as expected from the south-east and the British failed to find them before dawn, the distance between the two fleets would be no more than {{cvt|100|mi}}; the British would be detected by Japanese aerial reconnaissance at sunrise and be subject to air attack all day. Much the same could have been expected had Somerville still been on station when the Japanese arrived – as they did – from the south-west.<ref name="Boyd_369"/> Somerville's decision to refuel at Port T – rather than on Ceylon – on 2 April allowed the Eastern Fleet to avoid Nagumo a few days later, and likely saved the Eastern Fleet from destruction. The failure of the Japanese fleet to appear on 1–2 April led Somerville to mistakenly believe that the entirety, rather than a part, of Allied intelligence concerning Operation C was flawed. He detached ''Cornwall'', ''Dorsetshire'', and ''Hermes'', which were lost after being sent into areas overflown by Japanese aerial reconnaissance.<ref name="Boyd_370"/>

Andrew Boyd wrote,

{{quote|[Somerville] underestimated the risks he was running at least up to dusk on 5 April. He drew over-optimistic conclusions from the available intelligence, he grossly underestimated IJN air strength and he hazarded his fleet in direct contravention of his instructions from the chiefs of staff. Ceylon was not his finest hour.<ref name="Boyd_383">Boyd, p. 383</ref>}}

The disquieted Admiralty broadly agreed.<ref name="Boyd_383"/>

Somerville faced challenges not experienced by the RN in the Atlantic or Mediterranean. Japanese air superiority made it difficult to scout, close, and attack during the day. Radar-enabled night attack was the only viable offensive option. This was a high-risk strategy, careful positioning, luck, and Japanese errors nearly produced the conditions for a strike on the night of 5 April; the Japanese were within {{cvt|125|mi}} – 1-hour flight range in an Albacore – but accurate information on the Japanese vector was missing. Even then, it required experienced air crews to find their targets at night, using radar with a range of just {{cvt|20|mi}} and new tactics.<ref name="Boyd_382">Boyd, p. 382</ref>

==References==

===Notes===
{{reflist}}

===Articles===
* {{cite journal |last1=Stuart |first1=Robert |date=2014 |title=Air Raid Colombo, 5 April 1942: The Fully Expected Surprise Attack |url=http://www.rcaf-arc.forces.gc.ca/en/cf-aerospace-warfare-centre/elibrary/journal/2014-vol3-iss4-06-air-raid-colombo-5-april-1942.page |journal=Royal Canadian Air Force Journal |volume=3 |issue=4 |publisher=[[Department of National Defence (Canada)|Department of National Defence of Canada]] |access-date=4 January 2021}}
* {{cite journal |last1=Stuart |first1=Robert |date=2006 |title=Leonard Birchall and the Japanese Raid on Colombo |url=http://www.journal.forces.gc.ca/vo7/no4/stuart-eng.asp |journal=Canadian Military Journal |volume=7 |issue=4 |publisher=[[Department of National Defence (Canada)|Department of National Defence of Canada]] |access-date=4 January 2021}}
* {{cite journal |last1=Tully |first1=Anthony |last2=Yu |first2=Lu |date=2015 |title=A Question of Estimates: How Faulty Intelligence Drove Scouting at the Battle of Midway |url=https://digital-commons.usnwc.edu/nwc-review/vol68/iss2/6/ |journal=Naval War College Review |volume=68 |issue=2 |publisher=[[Naval War College|United States Naval War College]] |access-date=8 September 2020}}

===Books===
{{refbegin}}
* {{cite book |last=Boyd |first=Andrew |year=2017 |title=The Royal Navy in Eastern Waters |publisher=Seaforth |isbn=978-1-4738-9248-4}}
* {{cite book |last1=Boyd |first1=Carl |last2=Yoshida |first2=Akihiko |year=2013 |title=The Japanese Submarine Force and World War II |publisher=Naval Institute Press |location=Annapolis, MD |isbn=978-1-5575-0015-1|name-list-style=amp}}
* {{Cite book |last=Ireland |first=Bernard |title=Cuirassés du 20e siècle |date=2004 |publisher=Airelles |series=Airelles référence |location=St-Sulpice |language=fr |trans-title=20th Century Battleships |isbn=978-2-88468-038-7}}
* {{Cite book |last=Macintyre |first=Donald |title=Famous Fighting ships |publisher=Hamlyn |year=1975 |isbn=978-0-600-35486-4}}
* {{Cite book |last1=Parshall |first1=Jonathan |last2=Tully |first2=Anthony |year=2005 |title=Shattered Sword: The Untold Story of the Battle of Midway |name-list-style=amp |publisher=Potomac Books |location=Dulles, VA |isbn=1-57488-923-0 |url=https://archive.org/details/shatteredswordun0000pars |url-access=registration |via=Archive Foundation}}
* {{cite book| last = Roskill| first = Stephen| year = 1956| url = http://www.ibiblio.org/hyperwar/UN/UK/UK-RN-II/index.html| title = War at Sea 1939–1945, Volume II, the Period of Balance |series=United Kingdom Military Series| location = London| publisher = HMSO| access-date = 2015-09-02 }}
* {{cite book |last1=Shores |first1=Christopher |first2=Brian |last2=Cull |first3=Yasuho |last3=Izawa |year=2002 |title=Bloody Shambles: The Drift to War to the Fall of Singapore |volume=I |publisher=Grub Street |location=London |name-list-style=amp |isbn=}}
* {{cite book |last1=Shores |first1=Christopher |first2=Brian |last2=Cull |first3=Yasuho |last3=Izawa |year=1993 |title=Bloody Shambles: The Defence of Sumatra to the Fall of Burma |volume=II  |publisher=Grub Street |location=London |name-list-style=amp |isbn=978-0-94-881767-0}}
* {{Cite book |last1=Warner |first1=Oliver |series=Encyclopédie visuelle Elsevier |title=Histoire de la guerre sur mer: des premiers cuirassés aux sous-marins nucléaires |last2=Bennett |first2=Geoffrey |last3=Macyntire |first3=Donald G.F.W. |last4=Uehling |first4=Franck |last5=Wettern |first5=Desmond |last6=Preston |first6=Antony |last7=Mordal |first7=Jacques |publisher=Elsevier Séquoia |location=Paris Bruxelles |language=fr |others=Translated from the English |year=1976 |isbn=978-2-8003-0148-8}}
{{refend}}

===Further reading===
* {{cite book |last=Brown |first=David |year=1990 |title=Warship Losses of World War Two |publisher=Naval Institute Press |location=Annapolis, MD |isbn=1-55750-914-X}}
* {{cite book |last=Crusz |first=Noel |title=The Cocos Islands Mutiny |year=2001 |publisher=Fremantle Arts Centre Press |location=Fremantle |isbn=978-1-86-368310-4}}
* {{cite book |last=Dull |first=Paul S. |year=1978 |title=A Battle History of the Imperial Japanese Navy, 1941–1945 |publisher=Naval Institute Press |location=Annapolis, MD |isbn=0-87021-097-1 |url=https://archive.org/details/battlehistoryofi0000dull |url-access=registration |via=Archive Foundation}}
* {{cite book |last=Gill |first=G. Hermon |year=1985 |orig-year=1953 |url=http://www.awm.gov.au/histories/chapter.asp?volume=25 |title=Royal Australian Navy, 1942–1945 |volume=II |series=[[Australia in the War of 1939–1945]] |location=Canberra |publisher=[[Australian War Memorial]] |isbn=978-0-00-217480-0 |archive-date=27 August 2006 |archive-url=https://web.archive.org/web/20060827072128/http://www.awm.gov.au/histories/chapter.asp?volume=25 |url-status=dead}}
* {{cite book |last=Morison |first=Samuel Eliot |author-link=Samuel Eliot Morison |orig-year=1958 |year=2001 |series=[[History of United States Naval Operations in World War II]] |title=The Rising Sun in the Pacific 1931 – April 1942 |volume=III |publisher=Castle Books |location= Edison, NJ |isbn=0-7858-1304-7}}
* {{cite book |last1=Piegzik |first1=Mikhal A.|series=Asia@War No.31 |title=The Darkest Hour: The Japanese Naval Offensive in the Indian Ocean 1942 – The Opening Moves |volume=I |date=2022 |publisher=Helion |location=Warwick |isbn=978-1-915070-61-6}}
* {{cite book |last1=Piegzik |first1=Mikhal A.|series=Asia@War No. 33 |title=The Darkest Hour: The Japanese Naval Offensive in the Indian Ocean 1942 – The Attack Against Ceylon and the Eastern Fleet |volume=II |date=2022 |publisher=Helion |location=Warwick |isbn=978-1-804510-23-0}}
* {{cite book |last=Stille |first=Mark |year=2023 |title=Japan's Indian Ocean Raid, 1942 |series=Campaign |volume=396 |publisher=Osprey |isbn=978-1-47285-418-6}}

==External links==
{{Commons}}
* [http://www.navweaps.com/index_oob/OOB_WWII_Pacific/OOB_WWII_Indian_Ocean.htm Order of battle]
* [https://ww2db.com/battle_spec.php?battle_id=7 WW2DB.com: Raids into Indian Ocean]
* [https://web.archive.org/web/20070927234732/http://www.raf.mod.uk/history/ceylon.html Royal Air Force History: Battle for Ceylon]

{{coord missing|Indian Ocean}}

{{Authority control}}

[[Category:Conflicts in 1942]]
[[Category:Indian Ocean operations of World War II]]
[[Category:Military of British Ceylon]]
[[Category:Naval battles of World War II involving Japan]]
[[Category:1942 in Japan]]
[[Category:World War II raids]]
[[Category:Naval battles of World War II involving Canada]]
[[Category:Military history of Ceylon in World War II]]
[[Category:Naval battles and operations of World War II involving the United Kingdom]]
[[Category:March 1942]]
[[Category:April 1942]]
[[Category:Attacks on military installations in Sri Lanka]]
[[Category:Attacks on military installations in 1942]]
[[Category:Aerial bombing in Sri Lanka]]
[[Category:Airstrikes conducted by Japan]]
[[Category:Naval aviation operations and battles]]
[[Category:Attacks on naval bases]]