There is a book titled, "Hell Riders: The Charge of the Light Brigade" by Terry Brighton that mentions three men from the 8th Hussars and the 17th Lancers who served in regiments of the Union Army ( as I recall the 19th Penn Cav and a Mass Cav regiment), he further mentions officers of both sides who served in the CW that were Prussians, French and Russian. Not sure how much help that will be. It is unique that survivors of the Charge of the Light Brigade went on to serve in other wars. Most counted themselves lucky and left the service and enjoyed their remaining years.