Dagor Bragollach - The fourth great battle of the Wars of Beleriand

On a winter's night, Morgoth sent out rivers of flame from Thangorodrim, and the Mountains of Iron spewed fires and deadly fumes. The flames consumed the plain of Ard-galen, which was renamed Anfauglith. Many Elves perished as they tried to escape the fire, and the confusion caused by the flame and smoke hindered the defenders that watched Angband. Then Morgoth sent forth his armies, led by Glaurung, first of the Urulóki. Behind Glaurung came Balrogs and multitudes of Orcs, and they slaughtered anyone they came across. Thus the Siege of Angband was broken, and the forces of Morgoth were able to roam at will throughout the north. His enemies were decimated, and most of the Grey-elves fled south to Doriath, Nargothrond, Falas and Ossiriand. However, Morgoth could not completely destroy his foes as they scattered and hid in secret places, and he had himself been wounded.