World War II: Indian Ocean Raid

HMS Hermes sinking during World War II
HMS Hermes sinks on April 9, 1942. Public Domain

Indian Ocean Raid - Conflict & Dates:

The Indian Ocean Raid was conducted March 31 to April 10, 1942, during World War II (1939-1945).

Forces & Commanders


  • Vice Admiral Sir James Somerville
  • 3 carriers, 5 battleships, 7 cruisers, 15 destroyers


  • Vice Admiral Chuichi Nagumo
  • 6 carriers, 4 battleships, 7 cruisers, 19 destroyers

Indian Ocean Raid - Background:

Following the Japanese attack on the American fleet at Pearl Harbor on December 7, 1941 and the start of World War II in the Pacific, the British position in the region quickly began to unravel. Beginning with the loss of Force Z off Malaysia on December 10, British forces surrendered Hong Kong on Christmas before losing the Battle of Singapore on February 15, 1942. Twelve days later, the Allied naval position in Dutch East Indies collapsed when the Japanese soundly defeated American-British-Dutch-Australian forces at the Battle of the Java Sea. In an effort reestablish a naval presence, the Royal Navy dispatched Vice Admiral Sir James Somerville to the Indian Ocean as Commander-in-Chief, Eastern Fleet in March 1942. To support the defense of Burma and India, Somerville received the carriers HMS Indomitable, HMS Formidable, and HMS Hermes as well as five battleships, two heavy cruisers, five light cruisers, and sixteen destroyers.

Best known for his reluctant attack on the French at Mers el Kebir in 1940, Somerville arrived on Ceylon (Sri Lanka) and quickly found the Royal Navy's principal base at Trincomalee to be poorly defended and vulnerable. Concerned, he directed that a new forward base be constructed on Addu Atoll six hundred miles to the southwest in the Maldives. Alerted to the British naval build up, the Japanese Combined Fleet directed Vice Admiral Chuichi Nagumo to enter the Indian Ocean with the carriers Akagi, Hiryu, Soryu, Shokaku, Zuikaku, and Ryujo and eliminate Somerville's forces while also supporting operations in Burma. Departing Celebes on March 26, Nagumo's carriers were supported by a variety of surface vessels as well as submarines.

Indian Ocean Raid - Nagumo Approaches:

Warned of Nagumo's intentions by American radio intercepts, Somerville elected to withdraw the Eastern Fleet to Addu. Entering the Indian Ocean, Nagumo detached Vice Admiral Jisaburo Ozawa with Ryujo and ordered him to strike British shipping in the Bay of Bengal. Attacking on March 31, Ozawa's aircraft sank 23 ships. Japanese submarines claimed five more along the Indian coast. These actions led Somerville to believe that Ceylon would be struck on April 1 or 2. When no attack materialized, he decided to dispatch the older Hermes back to Trincomalee for repairs. The cruisers HMS Cornwall and HMS Dorsetshire as well as the destroyer HMAS Vampire sailed as escorts. On April 4, a British PBY Catalina succeeded in locating Nagumo's fleet. Reporting its position, the Catalina, flown by Squadron Leader Leonard Birchall, was soon downed by six A6M Zeros from Hiryu.

Indian Ocean Raid - Easter Sunday:

The next morning, which was Easter Sunday, Nagumo launched a large raid against Ceylon. Making landfall at Galle, the Japanese planes moved up the coast to strike at Colombo. Despite the warning the previous day and sightings of the enemy aircraft, the British on the island were effectively taken by surprise. As a result, the Hawker Hurricanes based at Ratmalana were caught on the ground. Conversely, the Japanese, who were unaware of the new base at Addu, were equally taken aback to find that Somerville's ships were not present. Striking the available targets, they sank the auxiliary cruiser HMS Hector and the old destroyer HMS Tenedos as well as destroyed twenty-seven British aircraft. Later in the day, the Japanese located Cornwall and Dorsetshire which were en route back to Addu. Launching a second wave, the Japanese succeeded in sinking both cruisers and killing 424 British sailors.

Putting out from Addu, Somerville sought to intercept Nagumo. Late on April 5, two Royal Navy Albacores spotted the Japanese carrier force. One aircraft was quickly downed while the other was damaged before it could radio an accurate spotting report. Frustrated, Somerville continued to search through the night in the hopes of a mounting an attack in the dark using his radar-equipped Albacores. These efforts ultimately proved fruitless. The next day, Japanese surface forces sank five Allied merchant vessels while aircraft destroyed the sloop HMIS Indus. On April 9, Nagumo again moved to strike Ceylon and mounted a large raid against Trincomalee. Having been alerted that an attack was imminent, Hermes departed with Vampire on the night of April 8/9.

Indian Ocean Raid - Trincomalee & Batticaloa:

Hitting Trincomalee at 7:00 AM, the Japanese struck targets around the harbor and one aircraft conducted a suicide attack into a tank farm. The resulting fire lasted a week. Around 8:55 AM, Hermes and its escorts were spotted by scout plane flying from the battleship Haruna. Intercepting this report, Somerville directed the ships to return to port and attempts were made to provide fighter cover. Shortly thereafter, Japanese bombers appeared and commenced attacking the British ships. Effectively unarmed as its aircraft had been landed at Trincomalee, Hermes was hit around forty times before sinking. Its escorts also fell victim to the Japanese pilots. Moving north, Nagumo's planes sank the corvette HMS Hollyhock and three merchant ships. The hospital ship Vita later arrived to pick up survivors.

Indian Ocean Raid - Aftermath:

In the wake of the attacks, Admiral Sir Geoffrey Layton, Commander-in-Chief, Ceylon feared that the island would be the target of invasion. This proved not to be the case as the Japanese lacked the resources for a major amphibious operation against Ceylon. Instead, the Indian Ocean Raid accomplished its goals of demonstrating Japanese naval superiority and forcing Somerville to withdraw west to East Africa. In the course of the campaign, the British lost an aircraft carrier, two heavy cruisers, two destroyers, a corvette, an auxiliary cruiser, a sloop, as well as over forty aircraft. Japanese losses were limited to around twenty aircraft. Returning to the Pacific, Nagumo's carriers began preparing for the campaigns that would culminate with the Battles of the Coral Sea and Midway.

Selected Sources

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Your Citation
Hickman, Kennedy. "World War II: Indian Ocean Raid." ThoughtCo, Aug. 26, 2020, Hickman, Kennedy. (2020, August 26). World War II: Indian Ocean Raid. Retrieved from Hickman, Kennedy. "World War II: Indian Ocean Raid." ThoughtCo. (accessed March 20, 2023).