Christianity among the Mongols  In modern times the Mongols are primarily Tibetan Buddhists, but in previous eras, especially during the time of the Mongol empire (13th–14th centuries), they were primarily shamanist, and had a substantial minority of Christians, many of whom were in positions of considerable power. Overall, Mongols were highly tolerant of most religions, and typically sponsored several at the same time. Many Mongols had been proselytized by the Church of the East (sometimes called "Nestorian") since about the seventh century, and some tribes' primary religion was Christian. In the time of Genghis Khan, his sons took Christian wives of the Keraites, and under the rule of Genghis Khan's grandson, Möngke Khan, the primary religious influence was Christian. The practice of Nestorian Christianity was somewhat different from that practiced in the West, and Europeans tended to regard Nestorianism as heretical for its beliefs about the nature of Jesus. However, the Europeans also had legends about a figure known as Prester John, a great Christian leader in the East who would come to help with the Crusades. One version of the legend connected the identity of Prester John with a Christian Mongol leader, Toghrul, leader of the Keraites. When the Mongols conquered northern China, establishing the Yuan dynasty (1271–1368), the Church of the East was reintroduced to China after a gap of centuries. As the Mongols further expanded, the Christian sympathies of the court, primarily through the influential wives of the khans, led to changes in military strategy. During the Mongols' siege of Baghdad (1258), many of the citizens of the city were massacred, but Christians were spared. As the Mongols further encroached upon Palestine, there were some attempts at forming a Franco-Mongol alliance with the Christians of Europe against the Muslims. Mongol contacts with the West also led to many missionaries, primarily Franciscan and Dominican, traveling eastward in attempts to convert the Mongols to Roman Catholicism. The Mongols had been proselytised since about the seventh century. Many Mongol tribes, such as the Keraites, the Naimans, the Merkit, the Ongud, and to a large extent the Qara Khitai (who practiced it side-by-side with Buddhism), were Nestorian Christian. Genghis Khan himself believed in traditional Mongolian shamanism, but was tolerant of other faiths.