	Cossack was a dark chestnut horse standing 15.2 hands high, described by the "Farmer's Magazine" as having a "neat blood-like head", "clean shoulders" and "very muscular quarters". He was sired by the Northumberland Plate winner Hetman Platoff out of the mare Joannina, a descendant of the influential broodmares Filagree, Web and Penelope.