The Sixth corps was commanded by Franklin, and was composed of Smith's and Slocum's divisions, old soldiers of the Peninsula. A portion of them were engaged in the battle of Williamsburg. Smith's division was in the fight at Fair Oaks; and Slocum crossed to the north bank of the Chickahominy, in season to save Fitz-John Porter from annihilation in the battle of Gaines's Mills. They held the rear at White-Oak Swamp, and had borne their share in the battle of Malvern. The Fifth corps was commanded by Porter, and was composed of Sykes's division of Regulars and Morell's division; the same which had fought gloriously at Gaines's Mills, and Malvern, and reluctantly at Groveton. The Ninth corps was commanded by Burnside. He had four divisions,--Wilcox's, Sturgis's, Rodman's, and Cox's. Sturgis's and Rodman's troops were Burnside's own, which had a good record at Roanoke and Newbern. Wilcox's were of Sherman's army from Port Royal, and had seen some of the hardships of campaigning. They had been hurried up from the South, when it was discovered that Lee contemplated an invasion of the North. The Thirty-fifth Massachusetts in this corps had been but a few days in the service. How well they fought, we shall see hereafter. The troops commanded by General Cox were of the Kanawha division,--Western Virginia and Ohio soldiers, who had seen service among the mountains. The Twelfth corps, which had fought at Winchester and Cedar Mountain under Banks, was now commanded by General Mansfield. It contained but two divisions, Williams's and Greene's. Couch commanded an independent division, the troops which had stemmed the tide at Seven Pines. These corps composed the Army of the Potomac, which was organized into three grand divisions. Burnside commanded the right wing, having his own,--the Ninth and First corps. General Cox commanded the Ninth after the death of Reno at South Mountain, and the appointment of Burnside to the command of the grand division. The center was under the command of Sumner, and was composed of the Second and Twelfth corps,--his own and Mansfield's. The left wing was commanded by Franklin, and was composed of the Fifth and Sixth corps. General Lee's army was composed of the commands of Jackson, Longstreet, D. H. Hill, McLaw, and Walker. An estimate of his forces in the battle of Antietam, obtained from prisoners, deserters, and spies, is ninety-seven thousand. "It was fought for half a day with forty-five thousand men on the Confederate side, and for the remaining half with no more than an aggregate of seventy thousand,"[59] writes a Southern historian, who estimates McClellan's force at a hundred and thirty thousand. [Footnote 59: Pollard, Vol. II. p. 137.]