Bull Dog was by American Jefferson Davis Cohn at his Haras du Bois-Roussel in Alençon in France's Lower Normandy region, and raced for him as a homebred.

Bull Dog was a full brother to Sir Gallahad, who won the Poule d'Essai des Poulains and became a leading sire in North America.

Plucky Liege also produced two other colts, Bois Roussel and Admiral Drake, who went on to sire classic winners in Europe.

Plucky Liege was sired by Spearmint, a winner of the two most prestigious races in England and France in 1906, The Derby and the Grand Prix de Paris.

Because of his immediate success, American E. Dale Schaffer purchased Bull Dog in late 1930 and brought him to the United States too stand at his Coldstream Stud in Lexington, Kentucky.