The British Commonwealth Occupation Force (BCOF) was a part of the Allied occupation of Japan at the end of WWII...
An almost entirely Australian force by 1950, the presence of BCOF in Japan when the Korean War began enabled the rapid commitment of Australian sea, air and ground forces to the new conflict.
While the larger United States occupation force was charged with the military government of Japan, BCOF's task was the occupation of five Japanese provinces with a population of nineteen million, the demobilising of Japanese troops, and the dismantling of Japan's war-making capacity by the destruction of dumps of military equipment. BCOF began operations on 21 February 1946 and ceased in 1952 with the coming into force of the peace treaty on 28 April.
BCOF grew rapidly to 36,000 personnel by the beginning of 1947. Later in the year, owing to the success of the occupation mission and the requirement for BCOF units to deploy elsewhere, BCOF was rapidly reduced in size. BCOF was initially composed of Australians, British, Indians and New Zealanders. Australia was the major contributor, providing 16,200 personnel, the command and much of the administration. The Australian component of BCOF was drawn from the Australian Imperial Force (to become the Australian Regular Army in 1947), the Royal Australian Navy and the Royal Australian Air Force. The infantry component was the newly raised 34th Infantry Brigade Group (66th, 67th and 68th Battalions). The Navy provided HMAS Australia, Hobart, Shropshire, Culgoa, Arunta, Bataan, Murchison, Shoalhaven, Quadrant, Quiberon, Manoora, Kanimbla and Westralia. The RAAF units were 76, 77 and 82 Squadrons.
From 1948, with the departure of other contingents, BCOF became effectively an Australian force. The following year Australia too began to reduce its commitment. In May 1950 the Menzies government decided to withdraw all Australians by November. When the Korean War broke out in June this decision was reversed. There was then one infantry battalion, one fighter squadron and two ships. All of these were quickly deployed to Korea.