Although information about the life of Guillaume de Rubruck is very scarce, it is known that he met with famous people of his time. He was close to King Louis IX and on his behalf traveled to Mongolia. After returning to France, Rubruk sent the king a report that has survived to this day - "Notes on a journey to the eastern countries", containing information about the geography, manners and religion of the Mongol Empire.Travel Guillaume Rubruk gave a lot of new for its time information about the countries he visited, and his observation allowed him to notice many valuable and important details from the life of the Mongols of the XIII century. Rubruk's work is justly considered to be one of the most important sources on the history of the East available in Western European literature of the late Middle Ages.Having understood the circumstances at the Mongol court, Rubruk came to the decisive conclusion that all attempts to preach Catholicism in Mongolia were in vain. On his way back, he met a mission of five Dominican friars who had letters from the Roman Pope to Sartak and Munkae. They were going to preach Catholicism among the Tatars, but Rubruk explained to them in detail the hopelessness of the endeavor.