This really sells Grant short on his abilities to manage the Washington power structure in order to maximize his ability as commanding general:
General-in-Chief Henry W. Halleck, now outranked by his former subordinate, had forced Grant's hand by requesting to be relieved. Higher rank required Grant to assume overall command.Grant resolved the problem by arranging Halleck's appointment as chief of staff, leaving him in Washington to coordinate orders, freeing Grant to establish headquarters wherever he wished. Halleck's new post separated strategic command from administration, a crucial innovation in modern warfare. Grant avoided the role of military advisor to Lincoln and Secretary of War Edwin M. Stanton, a role congenial to Halleck, but intolerable to Grant, who intended to remain a commander, rather than a courtier, and to distance himself from politicians. Lincoln's Generals, Grant, Lincoln, and Unconditional Surrender, John Y. Simon, [pg 165-6]