I believe you are thinking of South Korea after the Korean War. The fact is that South Korea was basically a rogue territory grabbed by the resistance against the totalitarian Korean government. It resulted in the Us´s interest to step in and offered protection for total military control.
Not entirely either. Syngman Rhee's government (and his successor's government) was succeeded by Park Chung-hee as a result of the military coup. In the end, South Korea is still a authoritarian government during Park's government. The military still exists after Park was assassinated. Korean War occurred under Rhee's government. The path to democracy in South Korea was marked by a authorartian start that slowly becomes more peaceful as protests for greater democratic rights grew during Park's reign that led to eventual democratization that is conducted in peaceful manner and done without bloodshed. With that being said, the military still exists. Right now, they (or at least military officials) do not have as much say in the politics as they used to during Rhee's through Chun Doo-hwan's and Roh Tae-woo's governments (who were last two military officials to hold presidency in South Korea). Despite the transitions of power from one presidency to another, the military still exists.
