She had won several times on the racetrack, and came from good lines, including that of the famous jumping sire Bay Ronald.
Rantzau's sire, Foxlight, was one of the best stallions of the French national stud Le Haras du Pin, and also had the blood of Bay Ronald in his pedigree.
After a notable career at the track, Foxlight retired to stud duty where he was quite successful, producing both flat racers and steeplechasers.
Marcel Boussac went on to sell Rantzau to the French National Stud at Saint-Lô, and the stallion arrived at his new home in January 1951.
Although Ibrahim took the number-one spot again in 1973, Rantzau held onto fourth place in 1980, and again managed to rank number one in 1981, ten years after his death.