On the other hand, he had received a serious check, but his army remained intact and was as well prepared as ever to contest the campaign against Richmond, a campaign which had to be pushed to a successful conclusion before the war could end. The one grand opportunity of General McClellan's life was presented to him at the close of the battle of Antietam, and, failing to seize it, it never came again, and his military career ended with failure. Antietam was, in comparison to numbers engaged, the bloodiest battle of the Civil War. The Union loss was 2,108 killed; 9,549 wounded; 753 missing; total, 12,410. The Confederate loss was 1,886 killed; 9,348 wounded; 1,367 captured and missing; total, 12,601. The government was insistent that McClellan should push his advance against Richmond, but the favorable autumn wore away and the wet season arrived before a plan of campaign was formulated. This was to cross the Blue Ridge Mountains from Harper's Ferry, following the southeastern side of the range, leaving detachments to guard all the passes, and thus threaten the Confederate communications in the Shenandoah Valley. McCLELLAN SUPERSEDED BY BURNSIDE. Accordingly, on the 25th of October, the Army of the Potomac once more faced toward the Confederate capital. In the course of a week, it held the whole region southwest of the Blue Ridge and was near the army of General Lee, who fell back, cautiously followed at a safe distance by the Union commander. On the night of November 7th, while McClellan was talking in his tent with Burnside, a messenger arrived from Washington with an official order, relieving McClellan of the command of the Army of the Potomac and appointing Burnside as his successor. McClellan promptly turned over the care of the army to him, and, as directed, proceeded to Trenton, N.J., to await further orders. It may be added that General McClellan never served again in the army. He resigned in 1864, and was nominated the same year for President of the United States, but received only 21 electoral votes. He was Democratic governor of New Jersey 1878-1881, and died at his home in Orange, N.J., October 29, 1885. Burnside, although a fine corps commander, was not qualified to command the splendid body over which he was thus placed. He devoted a number of days to acquainting himself with his vastly enlarged duties. The six corps were united into three divisions of two corps each, Sumner commanding the right, Hooker the centre, and Franklin the left, while General Sigel had charge of a body of reserve. After consulting with General Halleck, it was decided that the Army of the Potomac should make a rapid march down the Rappahannock, cross by pontoon-bridges at Fredericksburg, and then advance upon Richmond by way of Hanover Court-House.