The Impeachers: The Trial of Andrew Johnson and the Dream of a Just Nation by Brenda Wineapple:
Andrew Johnson nominated William Tecumseh Sherman as General of the U.S. Army in command of the new military Division of the Atlantic. There were no military reasons for this new division, which included the District of Columbia, Maryland, Delaware, Virginia, and West Virginia, and there were no military reasons for the rank. Johnson had not consulted with the army beforehand. His sole aim was to humiliate General Grant.
Johnson was foolish to assume that Sherman would be willing to resettle in Washington, where his division would be headquartered, or that he would accept a position in rank equal to that of his friend. Sherman wearily told Johnson that the battle-tested Grant, the often-slandered Grant, the Grant who’d seen his soldiers slit the gullets of starving mules to satisfy their own hunger, this Grant now, today, had never been more upset. “If this political atmosphere can destroy the equanimity of one so guarded and prudent as he is,” Sherman explained, “what will be the result with one so careless and outspoken as I am? Therefore, with my consent, Washington never.”