With the Umayyad Caliphate's conquest of Hispania, Muslim Arabs and Berbers overthrew the previous Visigothic rulers and created Al-Andalus, which contributed to the Golden age of Jewish culture, and lasted for six centuries. It was followed by the centuries-long "Reconquista", terminated under the Catholic monarchs Ferdinand V and Isabella I. The legacy Catholic Spaniards then formulated the "Cleanliness of blood" doctrine. It was during this time in history that the Western concept of aristocratic "blue blood" emerged in a racialized, religious and feudal context, so as to stem the upward social mobility of the converted New Christians. Robert Lacey explains: