This was the Japanese seizure of the Andaman and Nicobar island groups in the Bay of Bengal to shield the left flank of the Japanese forces in the process of completing their 'B' (iii) conquest of Burma and also to deny the islands to the British for any possible preparation and launch of an amphibious assault to start the reconquest of southern Burma and/or northern Malaya (23 March 1942).
The Andaman islands group lies between Sumatra and Burma, and divides the Bay of Bengal from the Indian Ocean. The group is part of the island arc making up most of the Netherlands East Indies, but was a British possession in 1941. There are 572 islands in the group with a total area of 2,474 sq miles (6408 km²). The islands are rugged and covered with jungle, earthquakes are frequent, and in 1941 the islands had few inhabitants. The only significant settlement was Port Blair, which had only primitive facilities in 1941.
The Nicobar islands group is located on the Indonesian island arc between Sumatra and the Andaman islands group. The islands, of which there are 16 in three groups, have an area of 710 sq miles( 1840 km²), are mountainous and covered with jungle, and in 1941 had almost no resources or population. The bulk of the population and the administrative centre were located on Car Nicobar, the most northerly and also the flattest of the islands.
The Andaman and Nicobar island groups were most important to the British for the small naval base at Port Blair, whose garrison comprised a 300-man Sikh militia force commanded by 23 British officers. In January 1942 this garrison was reinforced by a Gurkha detachment of the 4/12th Frontier Force Regiment of Brigadier J. K. Jones’s Indian 16th Brigade, but after the fall of Rangoon on 8 March the British decided that defence of Port Blair was impossible and withdrew the Gurkhas.
The occupation was the task of Vice Admiral Noboru Hirata’s 1st Southern Expeditionary Fleet. On 23 March 1942 one battalion of Lieutenant General Renya Mutaguchi’s 18th Division and the 9th Base Force, carried in the 8,407-ton Kinugasa Maru, arrived by sea with the support of 10 other ships, namely the training cruiser Kashii, escort vessel Shumushu, minelayer Hatsutaka, converted gunboat Eiko Maru, minesweepers W-1, W-3 and W-4 of the 1st Minesweeper Division, and minesweepers Choko Maru, Shonan Maru No. 7 and Shonan Maru No. 5 of the 91st Special Minesweeper Division. Limited air support was provided by the floatplanes of the seaplane tender Sagara Maru, which operated in the waters to the east of the Nicobar islands group.
The invasion force was escorted by the light cruiser Yura and destroyers Amagiri, Asagiri, Yugiri and Shirakumo of the Invasion Force Escort Unit No. 1, with close cover provided by the light cruiser Sendai of the 19th Destroyer Division and destroyers Isonami, Uranami and Ayanami of the 20th Destroyer Division, and distant cover provided by the light carrier Ryujo and heavy cruiser Chokai (flag) of the 4th Carrier Division, heavy cruisers Kumano, Suzuya, Mikuma and Mogami of the 7th Cruiser Division, and destroyers Fubuki, Hatsuyuki, Shirayuki and Murakami of the 11th Destroyer Division.
Wholly outnumbered and outgunned, the Sikh militia offered no resistance, and its men were then disarmed and interned, though many of them later re-enlisted in the Indian National Army headed by the anti-British Subhas Chandra Bose. The British officers were sent to prisoner-of-war camps in Singapore, while Chief Commissioner Waterfall, Deputy Commissioner Major A. G. Bird, and other British civilian leaders were imprisoned locally. The islands were placed under the command of an Indian National Army officer, Colonel Bucho.
Japanese aircraft started to arrive on 26 March, and by the end of that month the islands were garrisoned by 600 men of Colonel (from February 1944 Major General) Yoshisuke Inoue’s 35th Independent Mixed Brigade in the Andaman islands group and Colonel (from February 1944 Major General) Toshio Itsuki’s 36th Independent Mixed Brigade in the Nicobar islands group, supported by an unknown number of policemen.
Accounts of the Japanese occupation describe many atrocities committed by Japanese troops, but no official records exist. Local women were pressed into service as ‘comfort women’, while men became forced labourers in the construction of a new airfield. An estimated 2,000 persons of the population of Port Blair, about 10% of the total, were killed by the Japanese during the occupation. Bird is known to have been executed on the orders of Bucho. The islands were nominally handed over to Indian rule under the authority of Bose on 29 December 1943, although the Japanese retained effective control until the end of the war.