In 1253, the Franciscan monk William of Rubruck reported numerous Europeans in Central Asia. It is also known that 30,000 Alans formed the royal guard (Asud) of the Yuan court in Dadu (Beijing). Marco Polo later reported their role in the Yuan dynasty in his book "Il Milione". It is said that those Alans contributed to a modern Mongol clan, Asud. John of Montecorvino, archbishop of Dadu (Khanbaliq), reportedly converted many Alans to Roman Catholic Christianity in addition to Armenians in China. In Poland and Lithuania, Alans were also part of the powerful Clan of Ostoja.