 Because McClellan failed to pursue Lee aggressively after Antietam , Lincoln ordered that he be removed from command on November 5 , 1862 . Maj. Gen. Ambrose Burnside assumed command of the Army of the Potomac on November 9 , 1862 . McClellan wrote to his wife , " Those in whose judgment I rely tell me that I fought the battle splendidly and that it was a masterpiece of art . ... I feel I have done all that can be asked in twice saving the country . ... I feel some little pride in having , with a beaten & demoralized army , defeated Lee so utterly . ... Well , one of these days history will I trust do me justice . " 
