Although a Democratic presidential elector in 1860, [Rawlins's] impassioned patriotism in 1861 attracted the attention of fellow townsman Ulysses S. Grant, who, when appointed brigadier general in August, offered Rawlins a staff position…. Rawlins's career intertwined with that of Grant for the rest of his brief life. Appointed adjutant with the rank of captain of volunteers, he was promoted to major (May 1862) after the battles of Fort Donelson and Shiloh. He then served as lieutenant colonel (November 1862-August 1863) during the Vicksburg campaign and was appointed brigadier general after Vicksburg fell. As adjutant he headed Grant's staff throughout the war, a position recognized formally when he was confirmed as brigadier general in the regular army in March 1865 to fill the newly created post of chief of staff to the commanding general. As chief of staff Rawlins organized headquarters paperwork, issued orders in his commander's name, and maintained offices in the field. He wrote clumsily, and Grant sometimes actually drafted orders for him to sign. Grant invariably drafted his own reports; Rawlins merely inserted copies of pertinent correspondence and verified facts and dates.
John Y. Simon, "Rawlins, John Aaron," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-00828.html.