J Force (sometimes referred to as “Jayforce”) was the name given to the New Zealand forces that were allocated to the British Commonwealth Occupation Force (BCOF) which occupied Japan following the end of the Second World War. On 21 August 1945 the New Zealand government agreed to contribute both a land and an air contingent.
Some troops who had recently returned from Europe with the 2nd Division got drafted to form a contribution (known as J-Force) toward the British Commonwealth Occupation Force (BCOF) in southern Japan. No. 14 Squadron RNZAF, equipped with Corsair fighters, and RNZN ships also joined BCOF. The force was deployed between 1946 and 1948, after which it was disbanded and its personnel repatriated to New Zealand.
Upon the surrender of Japan which ended the combat phase of the Second World War, Allied Forces, including New Zealanders, Australians, Canadians, and Indians, entered Japan as an occupying force in February 1946 to restore the peace, clean up debris from the atomic blast, help rebuild and direct Japan into becoming a democratic society. Within a week of the surrender Britain invited New Zealand to participate in the occupation of Japan. Due to its weakened condition at the end of the war Britain lacked the resources to provide a force by itself and it wanted members of Commonwealth to help supply sufficient numbers to show the United States that it was still a major power.
Source: Wikipedia, the free encyclopedia.