In March 1245, Pope Innocent IV authorized three missions to the Mongols, seeking information about this menace from the East and summoning Eastern Christian support against an anticipated Mongol onslaught. Only one of the missions, led by John of Plano Carpini, reached Mongolia—the first-known Western European party to reach East Asia by a land route. Traveling along the Silk Road’s new “Grasslands Route,” John and his companion Benedict reached the camp of Güyüg Khan, where they witnessed his installation as the Great Khan. Upon their return to the papal court in 1247, they delivered Güyüg’s letter demanding the submission of the pope and all the West’s princes. John also presented a detailed report on what he and Benedict had learned. A close reading of it reveals a master intelligence operative at work. In addition to presenting an overview of Mongol history and culture, Friar John’s report provides detailed information on the Mongols’ grand strategy, their military organization and armaments, and their battle tactics. Turning from intelligence gathering to military operations, he offered practical advice on how to meet and defeat the coming Mongol onslaught, an attack that, providentially for the West, never came. What did occur was a modest but significant migration of Western missionaries and merchants to East Asia in the century following this pioneering journey.