His brother, James M. McIntosh, served as a Confederate general until he was killed in the Battle of Pea Ridge.

McIntosh was born at Fort Brooke (Tampa), Florida Territory, while his father was on active duty in the Army.

He led his brigade in the campaign culminating in the Battle of Chancellorsville, winning plaudits from division commander Brig.

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.

[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.