Fields was a crewman aboard the Federation starship USS Enterprise under Captain James T. Kirk during the mid-2260s.
He was serving in the phaser room when the ship went into battle with the Romulans during the Neutral Zone Incursion around stardate 1709.
He reported a suspicious engineering crewman on deck 14 around stardate 2715 when there was a shipwide search for escaped mental patient Simon Van Gelder.
He was attached to a security division around that time when the children of Miri's world were discovered.
He was present during the Enterprise's first encounter with Khan Noonien Singh .