Parzival by Wolfram von Eschenbach was, according to the introduction to the Random House edition (1961, translation by Helen M. Mustard and Charles E. Passage) probably written during the years 1197-1212. It is divided into 16 books, and at the beginning of Book XV, Parzival and his half-brother Feirefiz, who have never met, encounter each other in a forest, neither knowing who the other is. They begin fighting, for adventure and the honor of their ladies. Each is an ever-victorious superhero type, and the author writes of Parzival that
whatever his hand had won hitherto was mere child's work. - If I could turn this story backwards, I would not want to take a chance on my hero.
They are both in danger, not only of death, but of disgrace for killing a kinsman. Fortunately, after several pages of fighting (with the author cheering Parzival on, and worrying about him at the same time), they take a break, and ask each other's names; and when they figure out who the other is, call off the fight.
With movies and tapes and CD's today, it is reasonable to think of turning a story back, and fantasizing that if one did so it might come out different; but it is harder to see what led von Eschenbach to the image of "turning this story backward".
I found Parzival fascinating reading. One can't say its characters are realistic, but neither are they stereotypes; rather, they continually behave in surprising and unpredictable ways. The author clearly loves all his characters, heros and villains alike.
Although the book was written after the beginning of the Crusades, "heathens" (i.e., Arabs) are not portrayed as evil, or even as generally opposed to Christians: Various Christian and heathen kingdoms are allied against various other Christian and heathen kingdoms. As for the religious difference, the author merely remarks that it is strange that these people, who know so much more science than Europeans, are ignorant of God's word. He seems to know nothing about their actual religion: he has Feirefiz (son of Parzival's Christian father and an Arab queen, who has raised him) swear by "Jupiter and Juno", perhaps the only heathen gods the author knew of.