Indian Ocean raid
The island of Ceylon commanded the Indian Ocean in early 1942. It controlled access to India and vital Allied shipping routes to the Middle East. Japanese forces needed these routes to support their Burma Campaign for control of India. The fall of Singapore on the 15th of February 1942 broke the United Kingdom's eastern defensive perimeter. This event exposed weak forces in Malaya to attack. The Japanese occupation of the Andaman Islands on the 23rd of March gave Japan control of the Andaman Sea. German and British authorities anticipated Japanese capture of Ceylon to solidify control of the Bay of Bengal. They feared disruption of British resupply for defence of India, Australia, and perhaps the Middle East. 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.
Admiral Isoroku Yamamoto issued the initial order to proceed with Operation C to the IJN's southern force on the 9th of March 1942. By the 16th of March, the plan was to depart from Staring Bay, Celebes, on the 26th of March. The target date for the attack on Colombo was set as the 5th of April. Admiral Chūichi Nagumo commanded a core of five aircraft carriers. These included Akagi, Sōryū, Hiryū, Shōkaku, and Zuikaku. Carrier Division 5 contained Akagi, Sōryū, and Hiryū. Carrier Division 2 contained Shōkaku and Zuikaku. The carriers were accompanied by all four heavy cruisers and both battleships. Japanese intelligence estimated the British Eastern Fleet strength reasonably accurately. They overestimated air strength on Ceylon. At least one submarine was sent to scout the Maldive Islands but failed to detect Port T at Addu Atoll. In three days, Vice Admiral Jisaburō Ozawa's Malay Force sank 23 merchant ships totaling over 130,000 gross registered tons.
Vice Admiral Sir James Somerville assumed command of the Eastern Fleet in March 1942. He divided the fleet into two groups based on speed. The faster Force A included aircraft carriers Illustrious and Indomitable. It also featured the modernized battleship HMS Renown as flagship. The slower Force B formed around the old carrier Hermes and four unmodernized light cruisers. Ships had never operated together before. Both ship and air crews were deficient in training. Allied intelligence identified only two carriers in the Japanese force. This information led Somerville to sail early expecting a smaller enemy. He planned to evade the Japanese during the day and close to launch torpedo strikes with radar-equipped Fairey Albacore bombers during the night. On the 7th of December 1941, air defences consisted of four obsolescent three-inch anti-aircraft guns at Trincomalee. By the 4th of April, there were 67 Hawker Hurricanes and 44 Fairey Fulmar fighters. A radar station existed each at Colombo and Trincomalee. There were 144 anti-aircraft guns available for defence.
At about 16:00 on the 4th of April, Squadron Leader Leonard Birchall spotted Nagumo's fleet south-east of Ceylon. His PBY Catalina flying boat transmitted the sighting before being shot down. At dawn, Japanese aerial reconnaissance aircraft flew out to a maximum of 250 miles. Shortly after 06:00, Nagumo's force began launching 91 bombers and 36 fighters. British pilots scrambled under fire when the first Japanese aircraft appeared over them at 07:45. The armed merchant cruiser HMS Dorsetshire, the Norwegian tanker Soli, and the old destroyer HMS Vampire were sunk. Three other ships were damaged. The port was damaged but not put out of action. Twenty of the 41 British fighters that took off were destroyed. Six Swordfish from 788 NAS arrived during the battle and were shot down. The Japanese lost seven aircraft. Nagumo changed course to west-southwest at 08:30. This unknowingly caused the opposing fleets to steam toward one another.
By the 8th of April, the Eastern Fleet had withdrawn and the Japanese fleet was approaching Trincomalee from the east. The Japanese fleet was detected by a RAF Catalina at 15:17 on the 8th of April. The harbour at Trincomalee was cleared that night. Hermes, escorted by HMS Enterprise, was sent south along the coast. A force of 80 Aichi D3A Val bombers attacked starting at 10:35. Both ships were sunk before noon near Batticaloa. Hermes was lost with 307 men after being hit by over forty bombs. Vampire was lost with 8 men. The nearby hospital ship Vita rescued 600 men. The corvette HMS Ceylon was hit by aircraft from Soryu and sunk with 53 men. Also sunk were the naval auxiliary Athelstone, the tanker British Sergeant, and the cargo ship Norviken. British land-based Fulmars arrived only after Hermes was sunk. Two Fulmars and four Vals were destroyed. Nagumo disengaged after recovering the strike on Hermes.
The Japanese inflicted disproportionate damage on the enemy but failed to destroy the main bulk of the British Eastern Fleet. They damaged port facilities, sank one carrier and two cruisers, and destroyed a third of enemy ground-based fighters. In return, the Japanese lost only 18 aircraft. The British interpreted their position as precarious. Ceylon and the Eastern Fleet were required to safeguard sea lines of communications through the Indian Ocean. The Eastern Fleet transferred its main base to Kilindini, Kenya in East Africa. This temporarily ceded the eastern Indian Ocean to the Japanese. Force A retired to Bombay. Somerville regularly deployed a fast carrier force to the central Indian Ocean over the next six months. By June, Ceylon was defended by three RAF squadrons and much improved radar and anti-aircraft defences. Ground defences were manned by two Australian army brigades. 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 shrank after early July.
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Common questions
What was the date of the fall of Singapore that broke the United Kingdom's eastern defensive perimeter?
The fall of Singapore occurred on the 15th of February 1942. This event exposed weak forces in Malaya to attack and allowed Japanese forces to advance toward Ceylon.
Which five aircraft carriers did Admiral Chūichi Nagumo command during the Indian Ocean raid?
Admiral Chūichi Nagumo commanded a core of five aircraft carriers including Akagi, Sōryū, Hiryū, Shōkaku, and Zuikaku. Carrier Division 5 contained Akagi, Sōryū, and Hiryū while Carrier Division 2 contained Shōkaku and Zuikaku.
When did Squadron Leader Leonard Birchall spot Admiral Nagumo's fleet south-east of Ceylon?
Squadron Leader Leonard Birchall spotted Nagumo's fleet at about 16:00 on the 4th of April. His PBY Catalina flying boat transmitted the sighting before being shot down by enemy fire.
How many merchant ships did Vice Admiral Jisaburō Ozawa's Malay Force sink within three days of the operation?
Vice Admiral Jisaburō Ozawa's Malay Force sank 23 merchant ships totaling over 130,000 gross registered tons in three days. This occurred as part of the initial phase of Operation C targeting Allied shipping routes.
What date was the attack on Colombo scheduled to take place during the Indian Ocean raid?
The target date for the attack on Colombo was set as the 5th of April. Japanese forces departed from Staring Bay, Celebes, on the 26th of March to execute this plan.