The Indian Ocean raid, also known as Operation C 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 Ceylon, but failed to locate and destroy the bulk of the British Eastern Fleet. The Eastern Fleet, commanded by Admiral Sir 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 waters, to be ready to deal with any attempt by the enemy to command those waters with light forces only." 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 Japanese occupation of the Andaman Islands on 23 March 1942 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 was relieved of naval duties to serve as a high-speed aircraft ferry shuttling available planes to Ceylon. 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