Complex sentence: He transferred to the Marine Corps Reserve's 25th Infantry Company in Huntington, West Virginia on June 9,1957, later becoming the (Interim) Commanding Officer of that unit as a warrant officer on June 6,1960.
Split into simpler sentences: He transferred to the 25th Infantry Company in Huntington, West Virginia on June 9,1957. He later became the (Interim) Commanding Officer of that unit as a warrant officer on June 6,1960.