Ystoria Mongolorum
Like some other famous medieval itineraries, it shows an absence of a traveler's or author's egotism, and contains, even in the last chapter, scarcely any personal narrative. Joannes was not only an old man when he went on this mission, but was, according to accidental evidence in the annals of his order, a fat and heavy man (vir gravis et corpulentus), insomuch that, contrary to Franciscan precedent, he rode a donkey between his preachings in Germany. In his narrative, however, he never complains.
His book, as to personal and geographical detail, is inferior to one a few years later by a younger brother of the same order, William of Rubruck or Rubruquis—who was Louis IX's most noteworthy envoy to the Mongols. In spite of these defects—and the credulity he shows in the Oriental tales, which is sometimes childishly absurd—Friar Joannes' Ystoria is, in many ways, the chief literary memorial of European overland expansion before Marco Polo. Among his innovative recommendations was development of light cavalry to combat Mongol tactics.
It first revealed the Mongol world to Catholic Christendom. The account of Tatar manners, customs and history is perhaps the best treatment of the subject by any Christian writer of the Middle Ages. He provided four lists: of nations conquered by the Mongols, nations that had (as of 1245–1247) successfully resisted, the Mongol princes, and witnesses to his narrative, including various Kiev merchants. All these catalogues, unrivaled in Western medieval literature, are of great historical value.
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