Born c. 1215, Rubruck, Flanders
Died c. 1295

Early in the thirteenth century, military leader Genghis Khan (c. 1162–1227) united the many scattered tribes of Mongolia into a powerful new nation. Over the next several decades his forces and those led by his sons and grandsons—some of whom would succeed him as the Great Khan (head military leader)—would sweep north into China and west into Europe, conquering most of Russia and crushing Hungarian and Polish armies. Mongol forces would invade Persia and overthrow the Islamic caliphate (domain) at Baghdad (what is now Iraq), creating a vast empire.

During this time, leaders of western Europe were fearful that the Mongols would expand farther west, into their territory. Their one great hope to avert this disaster was to convert the Mongols to Western Christianity. At the time of their greatest conquests, the Mongols practiced...