And so Grant came to momentous realization that in order to triumph, individual victories and defeats must necessarily matter less to him than they had to his predecessors. One defeat had been enough for each of them to abandon his strategy and withdraw to safety.
Grant was neither shrewder, nor more perceptive, than they, but he was readier to take risks and he possessed a quality that they did not -- perseverance, forged in the failures and misfortunes of his civilian life.
He might be just what the unlucky Army of the Potomac needed. Win or lose, Grant would go ahead. The romantic chivalry with which the war had begun had vanished in the red gore of Gettysburg and Chickamauga, replaced by simple mathematics: the ruthless application of greater numbers, firepower, and logistics to slowly destroy the Confederate army while moving inexorably southward -- described by Grant's aide, Lieutenant Colonel Horace Porter, as "a moving siege."
Joseph Wheelan, The Bloody Spring: Forty Days That Sealed The Confederacy's Fate (2014)