Rabban Bar Sauma, Mongol envoy to the pope
Rabban Bar Sauma, 1220-1294, was a Nestorian monk who became a diplomat for the Mongol khan and one of the most experienced travelers of his day. Born near present-day Beijing, and apparently of Uyghur descent, he embarked on a pilgrimage to Jerusalem, but because of the military situation he was forced to turn back. Instead he spent several years in Baghdad, which was a part of the Mongol, Persian-based, Ilkhanate. It was from here that he was dispatched to Europe on a diplomatic mission to seek an alliance with the French against the Mamluk rulers in Egypt who had defeated both the European Crusaders and the Mongol army itself.
Rabban Bar Sauma began his journey in 1287, accompanied by a retinue of assistants, including an Italian interpreter, and some 30 riding animals. He crossed the Black Sea to Constantinople where he had an audience with the Byzantine emperor. He continued on to Italy, sailing past Sicily where he observed a spectacular eruption of Mount Etna. He arrived in Rome, but too late to meet the pope who just had died. Instead he continued to Florence, Genoa and Paris where he spent a month as the guest of the French king. In Gascony, which at the time was under English control, he met the king of England. Both the French and the English were enthusiastic about the idea of military alliance with the Mongol khans, but the details were difficult to work out. Moreover, Edward I needed soldiers at home to put down rebellions by the Welsh and the Scots.
Going back to Rome, Bar Sauma was received by the newly elected pope who gave him communion on Palm Sunday, 1288. From here he went back to Baghdad with gifts and messages from various European rulers. This is also where he spent the rest of his days, compiling a book in which he recounted his far-flung travels. He died in Baghdad in 1294. The military alliance between the Europeans and the Mongol khan never happened.
Nestorian Christians, by the way, is the branch of Christianity which expanded eastward already in Antiquity, forming thriving congregations in Central Asia, India and China during the Tang dynasty. The Nestorians were independent of Rome and worshiped according to their own rituals. They denied that Christ could simultaneously be both god and man. Today a few hundred thousand Nestorian Christians remain.