John of Plano Carpini as a Franciscan friar is the first noteworthy European traveller in the Mongol Empire, to which he was sent on a formal mission by Pope Innocent IV. He wrote an excellent firsthand account of the Mongols called Ystoria Mongolorum (The History of the Mongols Whom We Call the Tartars). He successfully recorded a detailed account as the first direct authentic description of Asia based on his personal observation throughout the journey, which was formed not chronologically but thematically. Ystoria Mongolorum was written in two separate moments: the first redaction was realized shortly after his return to Lyon. The preface and Chapters 1-8 were written as a spy report to prepare for the reinvasion of Europe by the Mongols.; the second after some rest. Chapter 9 was entirely added in the second redaction and it looks like the attempt to reject the accusation of the text. The delivery of the papal letter was the official purpose of his visit to Mongolia. This purpose coincided with his sense of mission as a Franciscan friar. Incidentally. he was assigned a spy mission. But as the papal legate, John of Plano Carpini might not have accomplished the goal of converting Güyük Khan to Catholic faith or manifest the power of Almighty God and his supreme vicar, Pope Innocent IV. Furthermore, he received a very threatening letter from Güyük Khan hinting at the intention of reinvading Europe. It became clear that the Mongols’ intention was a reinvasion of Europe. Ystoria Mongolorum as the report of his visit to Mongolia written through this process helped Latin Christendom establish an initial impression on the Mongol Empire the Europeans feared, which was also beneficial for the preparation of a war.