Abstract
In a letter from pope Innocent IV to Alexander Nevsky, it was stated that Alexander’s father, Yaroslav Vsevolodovich, before his death agreed to convert to Catholicism ‘through the hands’ of John de Plano Carpini, the papal envoy to the Mongols. This message is often questioned or rejected as unreliable. Although there is no direct confirmation of this fact in Friar John’s report, other information he provides allows us to conclude that the papal envoy was with the dying prince until his death in order to administer the last rites – communion and unction – according to the rules of the Roman Church. As a result, Friar John violated one of the important ritual prohibitions in force among the Mongols: no one could visit the Khan’s headquarters for a year if he was present at the death of another person. Thus, the papal envoy jeopardized the failure of his diplomatic mission, which significantly devalued its results.