The Indian Ocean raid was a naval sortie by the Fast Carrier Strike Force of the Imperial Japanese Navy from 31 March to 10 April 1942 against Allied shipping and bases in the Indian Ocean. It was an early engagement of the Pacific campaign of World War II.

Following the destruction of the ABDA forces in the battles around Java in February and March, the Japanese sortied into the Indian Ocean to destroy British seapower there and support the invasion of Burma. The Japanese force, commanded by Admiral Chuichi Nagumo, had six carriers: Akagi, Ryujo, Hiryu, Soryu, Shokaku, and Zuikaku. This powerful force left Staring Bay , Celebes on 26 March 1942.

Signal decrypts provided the British commander of the Eastern Fleet, Vice Admiral Sir James Somerville with warning of the Japanese sortie, and he retreated to Addu Atoll in the Maldive Islands, expecting an attack on 1 April or 2 April.

The first raids were against shipping in the Bay of Bengal by the carrier Ryujo and six cruisers under the command of Admiral Jisaburo Ozawa. They sank 23 ships, and five more were sunk by submarines off India's west coast.

When the expected attack on Ceylon failed to take place, Somerville sent the slow carrier Hermes back to Trincomalee for repairs, escorted by the heavy cruisers Cornwall and Dorsetshire, and the Australian destroyer HMAS Vampire.

On 5 April 1942 the Japanese struck the naval base at Colombo, Ceylon, sinking the auxiliary cruiser Hector and the old destroyer Tenedos in the harbour, but losing eighteen planes to heavy flak. Then Japanese search planes discovered the Cornwall and Dorsetshire 200 miles southwest of Ceylon and sank them, killing 424 men.

On 6 April 1942 the Indian sloop Indus was sunk by air attack off the coast of Burma, off Akyab.

On 9 April 1942 the Japanese attacked the harbour at Trincomalee at 07:00. The British again had warning of the attack, and Hermes and her escorts had left the night before. They were returning to port when they were discovered at 08:55. Hermes had no aircraft on board, and so was defenceless when 70 bombers attacked her at 10:35 off Batticaloa. Hit 40 times, Hermes sank with the loss of 307 men. Vampire and the corvette Hollyhock were also sunk. The hospital ship Vita later picked up 590 survivors.

The sortie demonstrated Japanese superiority in carrier operations, but it did not destroy British naval power in the Indian Ocean. By making full use of signal intercepts, decryption, reconnaissance and superior radar, Somerville was able to save his fast carriers Indomitable and Formidable to fight another day.

See also

• South-East Asian Theatre of World War II
• Military history of Britain during World War II#Indian Ocean Disaster

External links

• Order of battle
• WW2DB.com: Raids into Indian Ocean