Affording missionary organisations the facility of using APO numbers was something that began with the US occupation of South Korea after WW2. The USA Military Government in Korea started its own parallel Army Post Office organisation on landing in September 1945. Approved missionary organisations, together with commercial suppliers to the military (usually Korean subsidiaries of US companies, could apply for APO privileges. At the beginning the HQ postal address of the XXIV Corps APO 235 was the primary number allocated. Approved users use other APO numbers, depending on their location.
In 1949, as the US Army was implementing the reduction of occupation forces, a similar reduction in the number of approved non-military users of APO facilities was begun. The story went as follows: