Fall of Gondolin

(1)	Morgoth's forces descend on Gondolin by night, unexpectedly emerging from the northern hills to take the city in a devastating surprise assault.
(2)	Led by Idril and Tuor, a band of survivors escape the fallen city by tunnel, emerging into the plains northward of Gondolin.
(3)	They escape into the northern mountains and pass through the cleft of Cirith Thoronath. There they are ambushed by Orcs and a Balrog, but are saved by Glorfindel and Thorondor's Eagles.
(4)	The survivors, including the young Eärendil, flee into the Vales of Sirion and travel on southward, eventually to reach the havens at the Mouths of Sirion.

The destruction of Gondolin by the forces of Morgoth, brought about by the treachery of Maeglin. Many were lost in the city's fall, not least King Turgon himself, but many also escaped by a secret way, among them Tuor and Idril and their young son Eärendil.