Indian Ocean Raid - Results

Results

The sortie demonstrated Japanese superiority in carrier operations, and exposed the unprofessional manner in which the RAF was run in the East, but it did not destroy British naval power in the Indian Ocean. It is arguable that, by making full use of signal intercepts, decryption, reconnaissance and superior radar, Somerville was able to save his fast carriers HMS Indomitable and Formidable to fight another day. However, it might equally be said that the blunders made by the Royal Navy meant that the main fleet from Addu was not able to make contact with Nagumo's force as it intended.

An invasion was feared by the British, who interpreted the Japanese failure to do so as due to heavy losses over Ceylon—and hence led to claims of a British victory. However, in reality the Japanese did not have the men, shipping or land based air power to spare for an invasion and occupation and were not even in a position to make a temporary occupation as a raid. The island did not face a real threat of invasion at any point during the war.

The island of Ceylon (Sri Lanka) 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 harbor and naval base, Trincomalee, was located on the island’s eastern coast. Japanese propaganda had an effect on many of the Sinhalese population, who now awaited their arrival.

The raid had allowed the Imperial Japanese Navy to demonstrate their mastery of the Indian Ocean and Bay of Bengal and their ability to seize territory by capturing the Andaman Islands. Despite losses, the British fleet escaped conflict by retiring; in view of the overwhelming superiority of the Japanese, particularly in carrier operations, this seems to have been a wise decision by Admiral Somerville. Japanese plans were already made for a submarine base on the island of Madagascar to attack Allied shipping routes; now a weakened Ceylon invited invasion, possibly with limited objectives, like the taking of Trincomalee, a more convenient base.

That the British expected invasion—from their mastery of Japanese codes and other sources—is borne out by a speech, the C. in C. of Ceylon, Admiral Sir Geoffrey Layton, made in mid-April, to personnel of the damaged airfield, at China Bay in Trincomalee Harbor. He warned them, ‘The Japanese Fleet has retired to Singapore, to refuel and rearm, and to organise an invasion force, which we think is coming back to attack us.’ He ended by saying, ‘He was going for re-enforcements, while you men here, must be prepared to fight to the last man to stop the Japanese.' The Admiral’s speech had a negative effect on personnel, particularly his reference to leaving the island for re-enforcements; afterwards he became known as ‘Runaway Layton’.

Three British army divisions came to strengthen Ceylon’s defences against a possible internal anti-British uprising; also measures to improve morale ensued, such as ensuring Sinhalese food rations were increased. Several minor mutinies against the British by native soldiers were quickly put down. Admiral Sir G. Layton remained in Ceylon for most of the war. Later, Ceylon would become an important base for the planned retaking of Malaya and Singapore.