original dog of the Alans, such as the German mastiff (Great Dane) and the French Dogue de Bordeaux, among others. Medieval Alania The Alans who remained in their original area of settlement north of the Caucasus (and for a time east of the Caspian Sea as well), came into contact and conflict with the Bulgars, the Gökturks, and the Khazars, who drove most of them from the plains and into the mountains. The Alans converted to Byzantine Orthodoxy in the first quarter of the 10th century, during the patriarchate of Nicholas I Mystikos. Al-Mas‘udi reports that they apostasized in 932, but this seems to have been short-lived. The Alans are collectively mentioned as Byzantine-rite Christians in the 13th century. The Caucasian Alans were the ancestors of the modern Ossetians, whose ethnonym derives from the name Ās (very probably the ancient Aorsi; al-Ma'sudi mentions al-Arsiyya as guards among the Khazars, and the Rus' called the Alans Yasi), a sister tribe of the Alans. The Armenian Geography uses the name Ashtigor for the most westerly located Alans, a name which survives as Digor and still refers to the western division of the Ossetians. Furthermore, in Ossetian, Asi refers to the region around Mount Elbrus, where they probably formerly lived. Some of the other Alans remained under the rule of the Huns. Those of the eastern division, though dispersed about the steppes until late medieval times, were forced by the Mongols into the Caucasus, where they remain as the Ossetians. Between the 9th and 12th centuries, they formed a network of tribal alliances that gradually evolved into the Christian kingdom of Alania. Most Alans submitted to the Mongol Empire in 1239–1277. They participated in Mongol invasions of Europe and the Song dynasty in Southern China, and the Battle of Kulikovo under Mamai of the Golden Horde. 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. According