Zelazny, Roger. "The Game of Blood and Dust"
Summary: Two aliens play at changing events in our past to compete in achieving their individual goals (success or failure for humanity).
Published: In Galaxy, April 1975; The Best from Galaxy Volume IV (ed. Jim Baen), Award 1976, Ace 1978 (0441054641); Science Fiction: Contemporary Mythology (eds. Patricia Warrick, Martin H. Greenberg and Joseph D. Olander), Harper & Row 1978; Galaxy: The Best of My Years (ed. Jim Baen), Ace 1980; The Last Defender of Camelot, Pocket 1980, Underwood/Miller 1981, Sphere 1986 (0722194137), Avon 1988 (0380703165), iBooks 2002 (0743435109), 2005 (1596871075BUY); and Futures Past (eds. Jack Dann and Gardner Dozois), q.v.
Original in: English.
Translation: Italian by Renato Pera as "Il gioco di sangue e polvere", in Il Meglio di Galaxy 4 (ed. Jim Baen), Mursia 1980.