William was born in Randolph County, Alabama, to Joseph and Nancy Buchanan (spelled multiple ways, including Buckhanon) of North Carolina. At age 19 he enlisted on July 2, 1862, in what was originally Company B (under Captain William T. Smith), 5th (Slaughter's) Battalion Cavalry, Hilliard's Legion, Alabama Volunteers, but later was merged into the 10th Regiment Cavalry. The next February he married Elizabeth Williamson of Heard County, Georgia, and spent the rest of his adult life there as a farmer.