NAVAL STAFF HISTORY SECOND WORLD WAR BATTLE SUMMARIES No.15 Naval Operations off Ceylon Mar.-Apr. 1942 (Also) No.16 Naval Operations at the capture of Diego Suarez (Operation "Ironclad") May 1942 [1943, British Navy]

The Battle of Ceylon (31 March-10 April 1942) was a major Imperial Japanese Navy operation intended to weaken Allied naval power in the Indian Ocean. Commanded by Admiral Ch¿ichi Nagumo, Japanese carrier forces struck British bases and shipping around Ceylon, demonstrating Japan's expanding maritime reach. Despite tactical success, the operation failed to destroy the British Eastern Fleet, which had withdrawn in advance under Admiral Sir James Somerville after receiving intelligence warnings. British attempts to locate and engage the Japanese carriers were frustrated by poor reconnaissance and limited tactical intelligence. The raid prompted British fears of a sustained Japanese offensive in the Indian Ocean. In response, the Eastern Fleet relocated its main base to East Africa, while defences on Ceylon were reinforced and Somerville retained his fast carrier force to counter limited Japanese incursions. These concerns also influenced Allied strategy in the region, contributing to the decision to seize Madagascar in May 1942 to deny its ports to Japanese forces and protect vital Allied shipping routes. As a result, Diego Suarez-and with it the security of the Cape Route to the East-was assured, and Madagascar was spared the fate of Indochina.