 Several attempts at a Franco @-@ Mongol alliance against the Islamic caliphates , their common enemy , were made by various leaders among the Frankish Crusaders and the Mongol Empire in the 13th century . Such an alliance might have seemed an obvious choice : the Mongols were already sympathetic to Christianity , given the presence of many influential Nestorian Christians in the Mongol court . The Franks ( Western Europeans and those in the Crusader States of the Levant ) were open to the idea of support from the East , in part owing to the long @-@ running legend of the mythical Prester John , an Eastern king in a magical kingdom who many believed would one day come to the assistance of the Crusaders in the Holy Land . The Franks and Mongols also shared a common enemy in the Muslims . However , despite many messages , gifts , and emissaries over the course of several decades , the often @-@ proposed alliance never came to fruition . 
