Complex sentence: Benjamin served during the American Civil War as a Colonel in the 43rd Regiment of the New York State Volunteers where he commanded the Light Division of Sixth Corps (part of the Army of the Potomac) as a Brevet Brigadier General.
Split into simpler sentences: Benjamin served during the American Civil War as a colonel in the 43rd Regiment of the New York State Volunteers. Later, he commanded the Light Division of Sixth Corps (part of the Army of the Potomac) as a Brevet Brigadier General.