Conversation so far:
When did Ronald Reagan join the military?
Ronald Reagan enlisted in the Army Enlisted Reserve on May 25, 1937.
What did Ronald Reagan do while in the military?
Ronald Reagan was commissioned a second lieutenant in the Officers' Reserve Corps of the Cavalry.
Where was Ronald Reagan stationed in the military?
Ronald Reagan's first assignment was at the San Francisco Port of Embarkation at Fort Mason, California, as a liaison officer of the Port and Transportation Office.
Where was Ronald Reagan stationed after Fort Mason, California?
Ronald Reagan applied for a transfer from the cavalry to the AAF  and was assigned to AAF Public Relations and to the First Motion Picture Unit in Culver City, California.
Did Ronald Reagan go into combat at all while in the military?
Due to his poor eyesight, Ronald Reagan was classified for limited service only, which excluded him from serving overseas.
How long was Ronald Reagan in the military for?
Ronald Reagan was separated from active duty on December 9, 1945, as an Army captain - 8 years since commissioning as a second lieutenant in 1937.

Question: Why was he separated from active duty?
Self-contained rewrite: Why was Ronald Reagan separated from active duty?