This was the British occupation of the Cocos islands group about mid-way between Australia and Ceylon in the Indian Ocean (February/March 1942).
As in World War I, the cable station on this island group was a vital link in Allied plans. The Allies were concerned that the islands might be seized as a base for German commerce raiding vessels operating in the Indian Ocean, and were also worried, from December 1941, that as Japanese forces had occupied neighbouring island groups they might also think to take the Cocos islands: to reduce the chances of the Japanese forces’ attention being caught, the seaplane anchorage between Direction and Horsburgh islands was not used, and orders were issued for radio transmitters not to be used except in emergencies.
After the fall of Singapore in February 1942, the administration of the islands was switched from Singapore to Ceylon, and West and Direction islands were placed under Allied military administration. The islands’ garrison initially consisted of a platoon of the King’s African Rifles, located on Horsburgh island with two 6-in (152-mm) guns to cover the anchorage, but was later bolstered by a detachment of the Ceylon Defence Force.
Despite the importance of the islands as a communication centre, the Japanese made no attempt either to raid or to occupy them and contented themselves with undertaking a reconnaissance flight about once a month. On 25 December 1942, the submarine I-166 bombarded the islands with its deck gun but caused no damage.
Later in the war two airstrips were built in 'Pharos' and three bomber squadrons were moved to the islands to fly raids against Japanese targets in South-East Asia and also to provide support during the planned 'Zipper' re-invasion of Malaya and reconquest of Singapore. The first aircraft to arrive were actually Supermarine Spitfire fighters of No. 136 Squadron, RAF, but then there arrived the Consolidated Liberator long-range heavy bombers of No. 321 (Netherlands) Squadron, and later of Nos 99 and 356 Squadrons.