Complex sentence: After commanding the battalion at Fredericksburg in December 1862, Latimer was promoted to major in March 1863 and became an officer in Richard Snowden Andrews's Battalion of Edward "Allegheny" Johnson's Division.
Split into simpler sentences: After commanding the battalion at Fredericksburg in December 1862, Latimer was promoted to major in March 1863. He became an officer in Maj. Richard Snowden Andrews's Battalion of Maj. Gen. Edward "Allegheny" Johnson's Division.