Complex sentence: Clinton Lawrence Rossiter served three years in the U.S. Naval Reserves between 1942 and 1946 as a gunnery officer, mostly on the USS Alabama (BB-60) in the Pacific theater, reaching the rank of lieutenant.
Split into simpler sentences: Clinton Lawrence Rossiter served 3 years in the U.S. Naval Reserves between 1942 and 1946. He was a gunnery officer, serving mostly on the USS Alabama (BB-60) in the Pacific theater, reaching the rank of lieutenant.