The 'Battle of Christmas Island' was a small engagement between Japanese and British forces for Christmas island in the Indian Ocean as 'X' (31 March/1 April 1942).

Assisted by a mutiny of Indian soldiers of the British Indian army against their British officers, men of the Imperial Japanese army were able to occupy Christmas island without any land-based resistance, but the US submarine Seawolf caused severe damage to the Imperial Japanese navy’s light cruiser Naka during the landings.

At the time, Christmas island was a British possession with an area of 52 sq miles (134.7 km²) under the administrative control of the Straits Settlement, and is situated 185 miles (298 km) to the south of Java. It was a perfect control post for the eastern Indian Ocean and it was an important source of phosphates, which were needed by Japanese industry. Since 1900, the island had been mined for its phosphate, and at the time of the battle there was a large labour force, consisting of 1,000 Chinese and Malays working under the supervision of a small group of British overseers. In addition, there were about 100 women and 200 children on the island.

After the 'J' occupation of Java, the Japanese Imperial General Headquarters issued orders on 14 March 1942 for the 'X' operation to occupy Christmas island. Rear Admiral Shōji Nishimura was assigned to command the 2^nd Southern Expeditionary Fleet's occupation force, with the light cruiser Naka as his flagship. The fleet also comprised the light cruisers Nagara and Natori, and the destroyers Minegumo, Natsugumo, Amatsukaze, Hatsukaze, Satsuki, Minazuki, Fumizuki and Nagatsuki, together with the oiler Akebono Maru and the troop transports Kimishima Maru and Kumagawa Maru carrying 850 men of the 21^st Special Base Force, 24^th Special Base Force and 102^nd Construction Unit.

Opposing this invasion force was a single 6-in (152.4-mm) gun which had been made in 1900 and had been mounted on Christmas island in 1940. The British garrison’a detachment of the Hong Kong and Singapore Royal Artillery numbered 32 men led by a British officer, Captain L. W. T. Williams. Williams’s force comprised one Indian officer, Subadar Muzaffar Khan, 27 Punjabi non-commissioned officers and gunners, and four British enlisted men.

A group of Punjabi troops, apparently believing Japanese propaganda concerning the liberation of India from British rule, and probably acting with the tacit support of some or all of the local Sikh police officers, mutinied. On 11 March, they shot and killed Williams and the four British enlisted men before hurling their bodies into the sea. The mutineers then locked the district officer and the island’s few other European inhabitants pending an execution that was apparently thwarted by the Japanese occupation.

At dawn on 31 March, a dozen Japanese bombers launched the attack, destroying the radio station. The mutineers signalled their intention to surrender, raising a white flag before the 850-man landing force had come ashore. The Japanese expeditionary force was able to disembark at Flying Fish Cove without opposition.

At 09.49 on the same morning, the US submarine Seawolf fired four torpedoes at Naka, but all missed. Seawolf attacked again at 06.50 on the following morning, firing three torpedoes at Natori, again missing. During the evening of this day, with her final two torpedoes launched at as range of only 1,100 yards (1005 m) Seawolf managed to hit Naka on her starboard side, near her No. 1 boiler. The damage was severe enough that Naka had to be towed to Singapore by Natori, and eventually was forced to return to Japan for a year of repairs. Following the hit, the other Japanese vessels depth charged the US submarine for more than nine hours, but it escaped.

Natori returned to Christmas island and withdrew all elements of the occupation force but a 20-man garrison detachment, to Banten Bay in the Dutch East Indies on 3 April. The Japanese gained phosphate rock which was loaded on the transport ships.

Following the occupation, the Japanese garrison attempted to put the Chinese and Malays to work, although many escaped farther inland to live off the land. The mutineers also became labourers, being used to clean storage bins. Production was very limited after the occupation and after 17 November, when the Nissei Maru was sunk by the US submarine Searaven while unloading at the wharf, phosphate production was halted. More than three-fifths of the island’s population, including the European prisoners, had been relocated to Java by December 1943. After the war, Christmas island was reoccupied by the UK in the middle of October 1945.[2]

In the post war period, seven Punjabi mutineers were traced and court-martialled in Singapore. The first six to be identified and tried were convicted on 13 March 1947. Five were sentenced to death, and one was sentenced to two years' imprisonment and discharge with ignominy. King George VI confirmed the death sentences on 13 August 1947. British rule in India ended shortly afterward, with India gaining independence and Pakistan being created before the executions could be carried out, and thus diplomatic issues had to be taken into account. In October 1947, a seventh mutineer was identified. He was also court-martialled and sentenced to death. An eighth soldier was identified as a participant in the mutiny but was never caught. On 8 December 1947, the death sentences were commuted to penal servitude for life after the governments of India and Pakistan made representations. After further arguments between the UK and Pakistan over where the sentences should be served, with the British demanding they serve nine years, the six prisoners were transferred to Pakistan in June 1955, after which the British government ended its interest in the case.