When Maj. Gen.Alfred Pleasonton reorganized the Cavalry Corps following the Battle of Brandy Station, McIntosh became a brigade commander in the second division led by Brig. Gen. David McM. Gregg. McIntosh was ill after Chancellorsville, but he was present when Gregg's division fought at the Battle of Gettysburg. He distinguished himself in the fight against J.E.B. Stuart on East Cavalry Field on July 3, 1863. When a Confederate attack led by Maj. Gen. Wade Hampton was at its height, McIntosh led some of his men in a flank attack on the attacking troopers.[1] McIntosh was injured by a fall from a horse in September 1863; and, after recovering from his injury, he was on duty in the defenses of Washington, D.C., in XXII Corps until May 1864.
McIntosh returned to the Army of the Potomac in time to be assigned a brigade in the third cavalry division of Brig. Gen. James H. Wilson during the Battle of the Wilderness. He continued in command in the operations of Maj. Gen. Philip Sheridan, including the beginning of the latter's Shenandoah Valley Campaign. McIntosh lost a leg because of a wound he received at the Third Battle of Winchester on September 19, 1864. Later he received brevet promotions of the ranks of major general, U. S. Volunteers, brigadier general, U.S. Army (regular army), and major general, U.S. Army. He retired from the army in 1870.
McIntosh died in New Brunswick. He is buried in the Elmwood Cemetery.