Participation in the British Commonwealth Occupation Force (BCOF) marked the first time that Australians were involved in the military occupation of a sovereign nation which it had defeated in war. BCOF participation in the Allied occupation of Japan was announced on 31 January 1946, though planning and negotiations had been in progress since the end of the war. The main body of Australian troops arrived in Japan on 21 February.
The entire BCOF force totalled 45,000, from Britain, India, New Zealand, and Australia. About 16,000 Australians served in BCOF, including an infantry contingent of 4,700, base units consisting of 5,300, an air force wing of 2,200, and 130 from the Australian General Hospital. The Royal Australian Navy (RAN) also had a presence in the region as part of the British Pacific Fleet. For two-thirds of the period of occupation the Commonwealth was represented solely by Australians, and throughout its existence BCOF was always commanded by an Australian officer.