Oates became a drifter, settling in Texas for a couple of years before returning to Alabama at the urging of his younger brother John, who the family had dispatched to locate him.

[3][4] Oates stated: His [Col. Chamberlain's] skill and persistency and the great bravery of his men saved Little Round Top and the Army of the Potomac from defeat.

Oates was wounded during the Battle of Fussell's Mill on the outskirts of Richmond, losing his right arm, which ended his active service.

[5] Oates resumed his law practice in Henry County, Alabama, and served as a delegate to the 1868 Democratic National Convention.

Oates married Sarah Toney of Eufaula on March 28, 1882, and they had one son, William Calvin, Jr., who eventually joined his father in the law practice.