Nírnaeth Arnoediad

In J. R. R. Tolkien's legendarium of Middle-earth, the (Dagor) Nírnaeth Arnoediad (IPA: [ˈdɑɡɒr ˈniːrnɑɛ̯θ ɑrˈnœdiɑd]; in later Sindarin rather IPA: [ɑrˈnɛdiɑd]) or (Battle of) Unnumbered Tears was the climactic Fifth Battle in the Wars of Beleriand.

In the almost two decades since their defeat in the Dagor Bragollach, the Noldor had lost control over the entire north of Beleriand, and were for the most part reduced to holding on defensively in Hithlum, Himring and Nargothrond. Gondolin was shut and unknown. The great deeds of Beren and Lúthien in defeating Sauron, overthrowing his fortress of Tol-in-Gaurhoth and wresting a Silmaril from Morgoth's Crown, as well as the military victories of Thingol on all the borders of his realm of Doriath, gave hope to the Noldor that Morgoth could still be defeated. In the year 468 of the Years of the Sun in the First Age, Maedhros began building an alliance capable of taking the war to Angband and regaining the lands of the Noldor.

...
Wikipedia