Complex sentence: During World War I O'Neal served overseas in the United States Army as an enlisted man in the Fifth Field Artillery in the First Division, and as an officer in the One Hundred and Third Field Artillery in the Twenty-sixth Division from 1917-1919.
Split into simpler sentences: During World War I O'Neal served overseas in the United States Army. O'Neal was enlisted in the Fifth Field Artillery in the First Division, and as an officer in the One Hundred and Third Field Artillery in the Twenty-sixth Division from 1917-1919.