In the second half of the 13th century, the Mongol empire and the Christian west began a series of diplomatic exchanges in an effort to organize a military alliance against their common enemy, the Mamluk Sultanate. From the west came Franciscan missionaries, sent by the Pope and by the French King Louis IX (ca. 1214-1270), while from the east came ambassadors of the Mongol sovereign Arghun (ca. 1250-1291), the Ilkhan of Persia from 1284 to 1291. After crushing defeats suffered at the hands of the Egyptian Mamluks, Arghun sent numerous ambassadors to Phillip IV of France (1268-1314), Edward I of England (1239-1307), and Pope Honorius IV (1210-1287). One of these ambassadors was the Nestorian monk Rabban Bar Sauma (ca. 1220-1294), who journeyed from Khān Bālīq to Persia in 1260, together with the future patriarch of the Church in Persia, Rabban Marcos (1245-1317).
In 1288, accompanied by two Genoese interpreters, Rabban Bar Sauma visited Constantinople, Sicily, Naples, Rome (where he learned of the death of Honorius IV), Tuscany, the Republic of Genoa, and numerous localities in France, where he was received by the kings of France and England. Returning to Rome, he was received by the new Pope, Nicholas IV (1227-1292), and returned to Baghdad in 1289. Despite these promising diplomatic engagements, the death of Arghun in 1291 and the definitive fall of the port of Saint John of Acre into Mamluk hands brought an end to the project of a Franco-Mongol alliance.
Rabban Bar Sauma recounted his voyages in a work composed in the Syriac language, describing especially the journey from Khān Bālīq to Persia, the vicissitudes of the patriarch Rabban Marcos, and his peregrinations through Europe. The volume is one of the first Mongol sources to describe the Mediterranean world and Christian Europe, documenting political and geographic interests comparable to those of the travel accounts of the evangelizing friars and Marco Polo (1254-ca. 1324). The Mongol-Christian diplomatic exchanges help to explain the impressive detail of information about Persia and the Mongol khanates of Central Asia found in the world map by Fra Mauro (active ca. 1430-ca. 1459/1464).