The Birth of Christ is the eucatastrophe of Man’s history. – Tolkien
For me, the last section of Tolkien’s On Fairy-Stories makes the slog that is the first half quite worth it. Tolkien’s exposition of eucatastrophe, “the happy turn” in a story, is unforgettable, an idea that has been expounded in countless places by numerous writers. Eucatastrophe is Tolkienian through-and-through. Not only is it a beautiful idea, but it’s a beautiful word as well.
Things get really wonderful when Tolkien speaks of the Birth of Christ – the Incarnation – as “the eucatastrophe of Man’s history.” Why does he say this? Tolkien was obsessed with the hopelessness and darkness of mankind’s case in the ancient world, something he probably picked up from his deep interest in mythology. In the Incarnation, man is re-directed towards his ultimate destiny as the benevolent viceroy of the cosmos, the blessed bridge between the heaven and earth.
The Incarnation is eucatastrophe because it is a surprise; like the appearance of the Eagles in various eucatastrophic moments of the Third Age, Christ first comes amid a desperate situation. Yes, the Jews hoped for a Messiah, but every indication is that they were looking for a great prophet and a warrior-king, one who would restore the kingdom of Israel to its Davidic pinnacle. Who would have thought that God would choose to draw so near to us as to become like us “in every way except sin,” indeed to renounce all of His rights as God in order to show us the beauty and triumph of the way of humility?
Eucatastrophe in Action
It seems that Tolkien was so intent on this idea that he worked it into The Lord of the Rings, for it is on March 25th, the traditional date of the Annunciation , that the One Ring is destroyed. And this is important: the One Ring is not finally destroyed by any Man, nor indeed by any hobbit, but by the invisible hand of the storyteller at work behind the scenes. Tolkien sets things up so that none of the three figures present  can claim credit for its destruction in the final analysis. No, the creature cannot save himself, not without divine aid, and though the great soul of the lowly hobbit is a sign of the greatness of humility itself, we see here that the hobbit is not even capable of finally putting the greatest of evils to death, of plunging the knife into its very heart.
Thus, we can see how fitting it is that Eagles are frequent instruments of eucatastrophe, for they represent the power and will of Manwë, the greatest of the angelic Valar. Their coming from the clouds is as the descent of a supernatural power.
Ask any Christian you know that has spent time dwelling upon it: the Incarnation is magical as a fairy-tale, and all the more so because we believe it to be as true as the fall of Rome. It is the wondrous event at the heart of everything, and yes, we mean everything. It is a thing wonderful to behold and to ponder. I get all misty-eyed when I think about it, and for good reason, for in it, we glimpse the mysterious ways of God Himself, saving and surprising us despite ourselves, drawing us ever closer to the deepness of a love vast as the cosmos.
1 – Subtract 9 months from December 25th and what do you get? More here.
2 – Frodo, Sam, and Gollum. While Gollum is ultimately responsible on an operative level of destroying the One Ring, he certainly does not will its destruction.