noted by Charles Knight, 31 January 2022.
Below is the US Army map (from the US National Archives) that designated conceptually the division of Korea after WWII. The division was intended as temporary occupation zones by the armies of the then-allied USSR & USA following the departure of the Japanese colonist army and administration.
The politics of Korean reunification and self-rule were not successfully negotiated in the 1940s or the 1950s and remain unresolved to this day. Today, there are strongly opposed ideological nationalists on both sides of the 38th parallel who refuse to settle political differences. However, it may well be China and the USA who have the greatest interest in Korea remaining divided because the peninsula’s division is thought to serve their geostrategic preferences.