United States Forces Korea (USFK) was established July 1, 1957.
Although the United States had been providing both military and economic aid to South Korea prior to 1957, the military aid had taken precedence as a result of the Korean War, and after the Armistice Agreement was signed the economic aid provided continued to be coordinated by the military. The US Presidential Private Advisory committee was responsible for separating the military and economic aid in 1957, with regional control of the military aid then being delegated to US Commander of the US Pacific Command in 1961. This change meant that the groups in charge of the planning and operation of military aid in Korea no longer reported to the US ambassador in Korea, but now reported to a newly appointed Commander of the US Forces in Korea: General George Decker.
More to come here.