Complex sentence: The War Department ordered him to report for duty in Arkansas, where he soon was commissioned as the Lieutenant Colonel of the 1st Arkansas Battalion and served on the staff of Lt. Gen. William J. Hardee, a former West Point instructor of infantry tactics.
Split into simpler sentences: The War Department ordered him to report for duty in Arkansas, where he soon was commissioned as the Lieutenant Colonel of the 1st Arkansas Battalion. He served on the staff of Lt. Gen. William J. Hardee, a former West Point instructor of infantry tactics.