Complex sentence: He attended high school and college in southern California, then served in the United States Air Force from 1947 to 1951, seeing action in the Korean Theater; later, he was in the United States Naval Reserve.
Split into simpler sentences: He attended high school and college in southern California, then joined the military. Between 1947 and 1951, Briggs served in the United States Air Force in the Korean Theater, and the United States Naval Reserve.