[1] After Korea was liberated from its status as a colony of the Empire of Japan at the end of World War II, the peninsula had been divided between the Soviet Civil Administration in the North and the United States Army Military Government in Korea in the South.
As part of the original agreement to establish both governments, they both intended to eventually withdraw from the Korean peninsula.
[1] On 14 November 1947, the UN General Assembly passed a resolution that created the UN Temporary Commission on Korea (UNTCOK).
It added a requirement to observe and report changes that "might lead to or otherwise involve military conflict in Korea".
[1] UNCOK was terminated on 7 October 1950, when the General Assembly created the United Nations Commission for the Unification and Rehabilitation of Korea (UNCURK).