Buchanan's assignment as Sergeant Major was recorded as a "detail", dated May 4, 1861. He served as Sergeant Major until the regiment reorganized in April 1862. Appointment as 1st Lieutenant and Adjutant didn't come until August 31, 1863, so the roll mentioned must carry a different date. He could not have served as adjutant until a vacancy existed. The correspondence describing the vacancy which Buchanan was nominated to fill is found with Johnston's 1st Mississippi Regt.

Buchanan's regular pay as a private of Co. "I" ($11 per month) can be found in his file with the 11th Mississippi Regt. He was a private throughout the period in which he served in the Signal Corps (Sept 1862 to Aug 1863).