The road to the peace treaty of 1582 signed at Jam Zapolski by King Stefan Batory of Poland and Tzar Ivan the Terrible was paved not only by teams of diplomats representing the two monarchs but also a mediator, the Jesuit Antonio Possevino. He was a special envoy of Pope Gregory XIII. In this article Possevino’s mission is discussed against the background of the long history of contacts between the West and Russia. His work is a characteristic record of a clash of cultures and mentalities. The author, a astute Vatican diplomat who uses his role of mediator in a military conflict to explore the opportunities of a union, is confronted with distrustful boyars whose only aim is to sign up a truce. Possevin’s work has attracted little attention in Polish historiography; it has not even been translated into Polish. Having reviewed the Russian and English editions of Moscovia (which differ considerably in their approach) the author of this article points out that we are still waiting for a monographic study which would recount not only Possevin’s mission to Muscovy but also the whole span of that wandering humanist’s epic life.