The narrative line shifts back to the end of Book V. Gwaihir, Lord of the Eagles, and his fellow eagles have indeed come to the Pelennor Fields, and they attack the Nazgul. The united forces of the West rout the last of Sauron's forces. Gandalf announces that the Quest of the Ring-bearer has succeeded. As the enormous shadow that is Sauron rises above Mordor, "terrible but impotent," scattering in the new wind, the forces of evil also scatter, disorganized, chaotic. Some plead for mercy; many more flee. The eagles fly into Mordor to retrieve Frodo and Sam from Mount Doom.
Sam and Frodo awake in the land of Ithilien, finding themselves attended by Gandalf. Gandalf tells Sam that the great shadow of Sauron has departed, and that Aragorn, the king, has healed them. They are reunited with Aragorn and with their other companions. Even amidst the joy of these reunions, however, the text reminds readers that Tolkien's tale is a tale of apocalypse-in this context, of endings and things passing away: Legolas' song of the Sea near the chapter's close haunts with its line, "For our days are ending and our years failing."
One of the outcomes of the war against Sauron, and one of the signs that a new age for Middle-earth is at hand, is that the peoples of the world have united in their struggle against their common enemy: "Out from the beleaguered hills knights of Gondor, Riders of Rohan, Dunedain of the North, close-serried companies, drove against their wavering foes." Ever since the events of The Hobbit, Tolkien has been stressing in his tales of Middle-earth the need for unity among diverse peoples; in this chapter, we see why that unity is so essential. It enables good to win a victory, a critical victory, over evil.
That victory over evil is the central eucatastrophic moment in The Lord of the Rings. Sam's question to Gandalf perfectly summarizes Tolkien's definition of this most critical moment in fairy-stories: "Is everything that is sad going to come untrue?" In his famous essay of 1947, "On Fairy-Stories," Tolkien defined eucatastrophe as follows: "In its fairy-tale-or otherworld-setting, it is a sudden and miraculous grace: never to be counted on to recur. It does not deny the existence of dyscatastrophe, of sorrow and failure; it denies (in the face of much evidence, if you will) universal final defeat and in so far is evangelium [Greek for "good news" or "gospel"], giving a fleeting glimpse of Joy, Joy beyond the walls of the world, poignant as grief" (as quoted in Shippey, p. 211). The eucatastrophe is real, but even it is not the final word on life, as Legolas' song about the elves departing over the Sea reminds readers. All life is transitory, and so the moments of "sudden and miraculous grace" must be seen and celebrated when they occur.
The Return of the King: Novel Summary: Book VI Chapter 4