Complex sentence: He eventually rose to the rank of master sergeant and served as the first sergeant of the U.S. Air Force Clinic at Eielson Air Force Base in Alaska, where he first saw the snow and mountains that later became recurring themes in his artwork.
Split into simpler sentences: He eventually rose to the rank of master sergeant and served as the first sergeant of the U.S. Air Force Clinic at Eielson Air Force Base in Alaska. In Alaska, Ross first saw the snow and mountains that later became recurring themes in his artwork.